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Effects of chewing on cognitive processing speed
Abstract
In recent years, chewing has been discussed as producing effects of maintaining and sustaining cognitive performance. We have reported that chewing may improve or recover the process of working memory; however, the mechanisms underlying these phenomena are still to be elucidated. We investigated the effect of chewing on aspects of attention and cognitive processing speed, testing the hypothesis that this effect induces higher cognitive performance. Seventeen healthy adults (20-34years old) were studied during attention task with blood oxygenation level-dependent functional (fMRI) at 3.0 T MRI. The attentional network test (ANT) within a single task fMRI containing two cue conditions (no cue and center cue) and two target conditions (congruent and incongruent) was conducted to examine the efficiency of alerting and executive control. Participants were instructed to press a button with the right or left thumb according to the direction of a centrally presented arrow. Each participant underwent two back-to-back ANT sessions with or without chewing gum, odorless and tasteless to remove any effect other than chewing. Behavioral results showed that mean reaction time was significantly decreased during chewing condition, regardless of speed-accuracy trade-off, although there were no significant changes in behavioral effects (both alerting and conflict effects). On the other hand, fMRI analysis revealed higher activations in the anterior cingulate cortex and left frontal gyrus for the executive network and motor-related regions for both attentional networks during chewing condition. These results suggested that chewing induced an increase in the arousal level and alertness in addition to an effect on motor control and, as a consequence, these effects could lead to improvements in cognitive performance.
... 뿐만 아니라 저작은 학 습, 기억, 주의력과 같은 인지기능의 유지 및 개선에 있어 긍정적인 영 향을 미치는 것으로 보고되고 있다 7) . Hirano 등 8,9) 17,18) . 또한 두 영역은 저작 시 주의과정(attentional process)에도 기여하는 것으로 알려져 있으며 8,9) . ...
... Hirano 등 8,9) 17,18) . 또한 두 영역은 저작 시 주의과정(attentional process)에도 기여하는 것으로 알려져 있으며 8,9) . 쐐기앞소엽의 경우 작업기억, 출처기억 및 자기참조 처리에 관여하고 있어 8,9,19) ...
... 또한 두 영역은 저작 시 주의과정(attentional process)에도 기여하는 것으로 알려져 있으며 8,9) . 쐐기앞소엽의 경우 작업기억, 출처기억 및 자기참조 처리에 관여하고 있어 8,9,19) ...
... This is not the case with trigeminal stimulation that occurs during chewing activity, which is based on both motor and sensory signals. Chewing improves cognitive performance [8], memory and learning [9][10][11] (see however [12,13]), and reduces the visual reaction time of subjects [8]. These effects are coupled with an increase in cerebral blood flow in the brain regions engaged in the performed task [8]. ...
... This is not the case with trigeminal stimulation that occurs during chewing activity, which is based on both motor and sensory signals. Chewing improves cognitive performance [8], memory and learning [9][10][11] (see however [12,13]), and reduces the visual reaction time of subjects [8]. These effects are coupled with an increase in cerebral blood flow in the brain regions engaged in the performed task [8]. ...
... Chewing improves cognitive performance [8], memory and learning [9][10][11] (see however [12,13]), and reduces the visual reaction time of subjects [8]. These effects are coupled with an increase in cerebral blood flow in the brain regions engaged in the performed task [8]. The time passed from the initial session (experimental session 1) is indicated in the grey bars. ...
Chewing improves visuospatial performance through locus coeruleus (LC) activation. The effects of bilateral and unilateral mastication were investigated in subjects showing different degrees of asymmetry in masseter electromyographic (EMG) activity during clenching and in pupil size at rest (anisocoria), which is a proxy of LC imbalance. Correlations between performance changes and asymmetry values were found in males, but not in females. Among males, subjects with low asymmetry values (balanced-BAL) were more sensitive than those with high asymmetry values (imbalanced-IMB) to bilateral and unilateral chewing on the side with higher EMG activity (hypertonic). The opposite was true for hypotonic side chewing. BAL subjects were sensitive to unilateral chewing on both sides, while in IMB subjects, hypertonic side chewing did not influence performance in either males or females. Bilateral chewing elicited larger effects in BAL subjects than in IMB subjects, exceeding the values predicted from unilateral chewing in both groups. Finally, pupil size and anisocoria changes elicited by chewing were correlated with asymmetry values, independent of sex. Data confirmed the facilitation of visuospatial performance exerted by chewing. Trigeminal asymmetries modulate the chewing effects, making occlusal rebalancing an appropriate strategy to improve performance.
... According to Ohta et al. (2017Ohta et al. ( , 2018, chewing enhances the autonomic nervous system activities of individuals aged ≥70 years. Moreover, gum chewing increases the activities in the inferior frontal gyrus, which is located in the frontal lobe (Hirano et al., 2013;Quintero et al., 2013). These studies have indicated that gum chewing affects frontal lobe activities. ...
... Mastication exercise using chewing gum was also found to improve working memory and learning ability (Fukushima-Nakayama et al., 2017;Jiang et al., 2015) and activate the parasympathetic nervous system (Ohta et al., 2017(Ohta et al., , 2018. Moreover, this exercise can improve reaction time in response to instructions, wakefulness, and cognitive functions (Hirano et al., 2013;Sakamoto et al., 2009). ...
... In addition, the elastic oral appliance chewing exercise may influence frontal lobe activities through a mechanism similar to gum chewing. Thus, this exercise may increase frontal lobe activities among denture wearers, thereby improving memory, learning ability, (Fukushima-Nakayama et al., 2017;Jiang et al., 2015), and speed of response to stimulation (Hirano et al., 2013;Sakamoto et al., 2009). In addition, our results suggest that the elastic oral appliance chewing exercise may increase frontal lobe activities without food or gum. ...
Objectives:
Chewing increases frontal lobe activity, resulting in improved memory, learning ability, and response reaction time. This study aimed to assess the effects of elastic oral appliance chewing on the activities and functions of the frontal lobe.
Methods:
The study participants were 15 healthy men with full dentulous (mean age, 27.4 ± 4.1 years). A prospective crossover design was used to assess frontal lobe activities and functions. Changes in frontal lobe activities were measured with near-infrared spectroscopy (NIRS). At baseline, the participants were assessed in the resting state. Changes in channels #7, representing right frontal lobe activities by NIRS, and #10, representing left frontal lobe activities, during the first and second chewing periods in a total of two periods were evaluated. Frontal lobe functions were measured using the Trail Making Test Part A (TMT-A) in the resting state and after elastic oral appliance or gum chewing. These values were compared with each period.
Results:
Elastic oral appliance chewing caused significant differences between the baseline and first chewing periods for channel #7 (p = .032) and significant differences between the baseline and second chewing periods for channels #7 and #10 (p < .001 and p < .001, respectively) using NIRS. Moreover, significant differences were found in the TMT-A results between the resting state and elastic oral appliance chewing (p = .04).
Conclusions:
Elastic oral appliance chewing improves frontal lobe activities to a level similar to that obtained with gum chewing.
... A very significant correlation was observed between anisocoria and EMG asymmetry, pupil size being larger on the side of higher EMG activity (hypertonic side). Correction of the trigeminal imbalance by an orthotic splint leads to a great reduction of the anisocoria, with an associated improvement in performance It is well known that chewing gum is used for sleepiness prevention during work, learning, and driving (50). In addition, it has been shown in the elderly that a decrease in the number of residual teeth is related to dementia onset (50). ...
... Correction of the trigeminal imbalance by an orthotic splint leads to a great reduction of the anisocoria, with an associated improvement in performance It is well known that chewing gum is used for sleepiness prevention during work, learning, and driving (50). In addition, it has been shown in the elderly that a decrease in the number of residual teeth is related to dementia onset (50). Moreover, the changes induced by bite wearing in pupil size and anisocoria were significantly related to the corresponding changes in EMG activity and asymmetry during clenching: this finding underlines the importance of sensorimotor trigeminal activity in determining the LC discharge level and the degree of its left-right imbalance. ...
... The rate of chewing and subjective force of chewing seems not to alter mood but have some limited effects on attention (41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54). Chewing gum during the workday was associated with higher productivity, and fewer cognitive problems raised cortisol levels in the morning and did not affect heart rate. ...
In recent years, chewing has been discussed as producing effects of maintaining and sustaining cognitive performance. It is reported that mastication improves cognitive function by activating cerebral cortical activity, and it is important to demonstrate the cognitive effects of masticatory training using various interventions. Recent studies emphasized that chewing gum can attenuate reductions in alertness, suggesting that chewing gum enhances worker performance. Several mechanisms have been proposed to account for the facilitation in performance observed when the gum is chewed during cognitive testing. Chewing gum during exposure to stress decreases plasma and salivary cortisol levels and reduces mental stress, although other studies report no such effect. In addition, chewing reduces stress-induced changes in central nervous system morphology, especially in the hippocampus and hypothalamus. However, further research on the alerting effects of chewing gum and possible improved test performance in these situations is needed.
... In the present study, sleepiness and fatigue did not differ, regardless of eating. It is speculated that rice balls are mainly carbohydrates, low in fat, and relatively slow to digest and absorb, and their granular shape is presumed to require chewing; in addition to the effect on motor control, chewing increases the arousal level and alertness [38]. Thus, these factors may have prevented a significant increase in drowsiness [38]. ...
... It is speculated that rice balls are mainly carbohydrates, low in fat, and relatively slow to digest and absorb, and their granular shape is presumed to require chewing; in addition to the effect on motor control, chewing increases the arousal level and alertness [38]. Thus, these factors may have prevented a significant increase in drowsiness [38]. Therefore, we concluded that the ingestion of the snack (352 kcal) did not change the subjects' sleepiness and fatigue. ...
... According to recent reviews, eating breakfast may result in acute improvements of memory, attention, and motor and executive function, although no conclusion about the effect of macronutrients on cognitive function has been reached [38]. The present result shows that a small snack lessened the decline in the number of correct answers on the UKT. ...
Background
Night shift workers might not eat due to their busy schedules during the night shift. However, food may not only satisfy hunger, but also affect performance and errors. The aim of this study was to clarify the effect of a snack on performance and errors during 2-day, 16-h, simulated night shifts.
Methods
A randomized, repeated-measure, crossover study was performed to investigate subjective and cognitive performance in 15 healthy female adults (mean age, 21.7 years) after they consumed a snack (352 kcal) during a simulated night shift (16:00 to 09:00) from October to November 2018. The participants were kept awake from waking up in the morning to the next day at 09:00. Subjects were tested for performance on the Uchida-Kraepelin test, as well as for subjective feeling, body temperature, psychomotor vigilance test, and heart rate variability, before and after they consumed the snack. One day before the experiment, all participants wore an actigraphy monitoring device to determine their sleep state.
Results
There was no difference between having (Snack condition) and not having (Skipping condition) the snack in sleep states the day before the experiment. On the day of the experiment, between 16:00 and 09:00, subjective sleepiness, fatigue, and body temperature were not different between the two conditions. Subjects maintained performance on the Uchida-Kraepelin test and showed a significant improvement in false starts on the psychomotor vigilance test, the primary outcome measure, in the Snack condition compared with the Skipping condition. The Snack condition was also associated with decreased high-frequency power, a decreased low-frequency power/high-frequency power ratio, and increased heart rate in the vagally mediated heart rate variability indices, which may reflect a higher ability to modulate cognitive and behavioral processes.
Conclusions
These results suggest that providing a snack to shift workers during night shifts might improve work safety and efficiency.
... In the present study, sleepiness and fatigue did not differ, regardless of eating. It is speculated that rice balls are mainly carbohydrates, low in fat and relatively slow to digest and absorb, and their granular shape is presumed to require chewing; in addition to the effect on motor control, chewing increases the arousal level and alertness [33]. Thus, these factors may have prevented a signi cant increase in drowsiness [33]. ...
... It is speculated that rice balls are mainly carbohydrates, low in fat and relatively slow to digest and absorb, and their granular shape is presumed to require chewing; in addition to the effect on motor control, chewing increases the arousal level and alertness [33]. Thus, these factors may have prevented a signi cant increase in drowsiness [33]. Therefore, we concluded that the ingestion of the snack (352 kcal) did not change the subjects' sleepiness and fatigue. ...
... According to recent reviews, breakfast consumption may result in acute improvements of memory, attention, and motor and executive function, although no conclusion about the effect of macronutrients on cognitive function has been reached [33]. The present result shows that a small snack lessened the decline in the number of correct answers on the UKT. ...
Background: Night shift workers might not eat due to their busy schedules during the night shift. However, diet may not only satisfy hunger, but also affect performance and errors.
The aim of this study was to clarify the effect of a snack on performance and errors during 2-day, 16-h simulated night shifts.
Methods: A randomized repeated-measure crossover study was performed to investigate subjective and cognitive performance in 15 healthy female adults (mean age, 21.7 years) after they consumed a snack (352 kcal) during a simulated night shift (16:00 to 09:00). The participants were kept awake from wake up in the morning to the next day at 09:00. Subjects were tested for performance on the Uchida-Kraepelin test, as well as for subjective feeling, body temperature, psychomotor vigilance test, and heart rate variability, before and after they consumed the snack. One day before the experiment, all participants wore an actigraphy monitoring device to determine their sleep state.
Results: There was no difference between the snack condition and the skipping condition in sleep states the day before the experiment. On the day of the experiment, between 16:00 and 09:00, subjective sleepiness, fatigue, and body temperature were not different between the two conditions. Subjects showed a significant improvement in performance on the Uchida-Kraepelin test and total errors on the psychomotor vigilance test, the primary outcome measure, when they consumed a snack compared with the skipping condition. In addition, the snack condition was associated with decreased high-frequency power, decreased low-frequency power/high-frequency power ratio, and increased heart rate, in the vagally mediated heart rate variability indices, which may reflect a higher ability to modulate cognitive and behavioral processes.
Conclusions: These results suggest that providing a snack to shift workers during night shifts might improve work safety and efficiency.
Trial registration: This study was registered with the University Hospital Medical Information Network-Clinical Trials Registry (UMIN-CRT registry ID: UMIN 000034345).
... Additionally, the NTS is linked to glutamatergic and GABAergic systems [13]. Through these projections and connections, an increase in the activity of trigeminal nuclei can have several behavioral and physiological consequences [14] including enhanced vigilance [15,16], accelerated mental information processing [17], reduced response delays [18], augmentation of the oxygen-dependent signal in cerebral blood flow, and mydriasis in response to tasks [19]. ...
... An increase in the activity of trigeminal nuclei can have several behavioral and physiological consequences [14][15][16][17][18][19]. There are several pathway mechanisms via which TNS has the potential to produce these effects, with one example pathway being via the LC. ...
tDCS is widely assumed to cause neuromodulation via the electric field in the cortex acting directly on cortical neurons. However, recent evidence suggests that tDCS may indirectly influence brain activity through cranial nerve pathways, notably the trigeminal nerve, but these neuromodulatory pathways remain unexplored. To investigate the first stages in this potential pathway we developed an animal model to study the effect of trigeminal nerve direct current stimulation (TN-DCS) on neuronal activity in the principal sensory nucleus (NVsnpr) and the mesencephalic nucleus of the trigeminal nerve (MeV). We conducted experiments on twenty-four male Sprague Dawley rats (n = 10 NVsnpr, n = 10 MeV during anodic stimulation, and n = 4 MeV during cathodic stimulation). DC stimulation, ranging from 0.5 to 3 mA, targeted the trigeminal nerve’s marginal branch. Concurrently, single-unit electrophysiological recordings were obtained using a 32-channel silicon probe, encompassing three 1-min intervals: pre, during, and post-stimulation. Xylocaine trigeminal nerve blockage served as a control. TN-DCS increased neuronal spiking activity in both NVsnpr and MeV, returning to baseline during the post-stimulation phase. The 3 mA DC stimulation of the blocked trigeminal nerve failed to induce increased spiking activity in the trigeminal nuclei. These findings provide empirical support for trigeminal nuclei modulation via TN-DCS, suggesting the cranial nerve pathways could play a role in mediating the tDCS effects in humans.
... Additionally, the NTS is linked to glutamatergic and GABAergic systems [11]. Through these projections and connections, an increase in the activity of trigeminal nuclei can have several behavioral and physiological consequences [12] including enhanced vigilance [13,14], accelerated mental information processing [15], reduced response delays [16], augmentation of the oxygen-dependent signal in cerebral blood ow, and mydriasis in response to tasks [17]. ...
... An increase in the activity of trigeminal nuclei can have several behavioral and physiological consequences [12][13][14][15][16][17]. There are several pathway mechanisms via which TNS has the potential to produce these effects, with one example pathway being vitae the LC. ...
Recent evidence suggests that transcranial direct current stimulation (tDCS) indirectly influences brain activity through cranial nerve pathways, particularly the trigeminal nerve. However, the electrophysiological effects of direct current (DC) stimulation on the trigeminal nerve (DC-TNS) and its impact on trigeminal nuclei remain unknown. These nuclei exert control over brainstem centers regulating neurotransmitter release, such as serotonin and norepinephrine, potentially affecting global brain activity. To investigate how DC-TNS impacts neuronal activity in the principal sensory nucleus (NVsnpr) and the mesencephalic nucleus of the trigeminal nerve (MeV), twenty male Sprague Dawley rats (n = 10 each nucleus) were anesthetized with urethane. DC stimulation, ranging from 0.5 to 3 mA, targeted the trigeminal nerve's marginal branch. Simultaneously, single-unit electrophysiological recordings were obtained using a 32-channel silicon probe, comprising three one-minute intervals: pre-stimulation, DC stimulation, and post-stimulation. Xylocaine was administered to block the trigeminal nerve as a control. DC-TNS significantly increased neuronal spiking activity in both NVsnpr and MeV, returning to baseline during the post-stimulation phase. When the trigeminal nerve was blocked with xylocaine, the robust 3 mA trigeminal nerve DC stimulation failed to induce increased spiking activity in the trigeminal nuclei. Our results offer initial empirical support for trigeminal nuclei activity modulation via DC-TNS. This discovery supports the hypothesis that cranial nerve pathways may play a pivotal role in mediating tDCS effects, setting the stage for further exploration into the complex interplay between peripheral nerves and neural modulation techniques.
... In the gum-chewing condition, MRTs of participants were significantly shorter than in the neutral condition. This finding is consistent with previous studies that investigated the relation between gum chewing and sustained attention (Hirano et al., 2013;Johnson et al., 2013;Miquel et al., 2019;Tucha & Simpson, 2011). These studies have reported a significant decrease in MRTs with the gum chewing conditions. ...
... These studies have reported a significant decrease in MRTs with the gum chewing conditions. Hirano et al. (2013) have reported that MRTs of participants significantly shortened in attentional network task during gum chewing. Johnson et al. (2013) have reported similar results with sustained attention response task. ...
Attention is a cognitive and behavioural process that can be affected by numerous internal and external factors. Gum chewing (GC) and repetitive motor activity (RMA) have previously been associated with improved attention. This study aimed to investigate the effects of GC and RMA on sustained attention in Attention Deficit-Hyperactivity Disorder (ADHD) A modified AX-CPT was applied to all participants (35 adults with ADHD and 30 healthy adults) for three conditions neutral, GC and RMA. There were significant differences between the groups in terms of the target responses for the neutral and the RMA conditions. A 2 (Groups) × 3 (Conditions) ANOVA revealed only a significant condition main effect. In GC and RMA, MRTs were decreased for both groups compared to the neutral condition. Both GC and RMA have improved sustained attention performance, similarly in ADHD and healthy adults so they may be used as easily accessible tools for improving attention.
... Thus, our data were consistent with the stimulated brain areas described in previous studies [37,40]. Several studies have reported that the recovery of oral function might stimulate improvement of cognitive functions, governed by the frontal lobe and hippocampus [42][43][44]. A previous study reported that the brain activity of the anterior cingulate cortex and left frontal gyrus were increased and attentional networks were affected by chewing [44]. ...
... Several studies have reported that the recovery of oral function might stimulate improvement of cognitive functions, governed by the frontal lobe and hippocampus [42][43][44]. A previous study reported that the brain activity of the anterior cingulate cortex and left frontal gyrus were increased and attentional networks were affected by chewing [44]. Chewing stimulated the neuronal activity within a network between the right prefrontal cortex and the hippocampus [38]. ...
Purpose: To reveal effects of improvement of masseter muscle activity on brain function in elderly people wearing complete dentures.
Methods: Subjects were 14 edentulous patients with a chief complaint of the inconvenience of their complete dentures. The surface electromyographic (EMG) activity of the masseter muscles was measured. Brain activities were analyzed with functional magnetic resonance imaging (fMRI), employing chewing gum as the task program. Cognitive functions were evaluated with Trail Making Test Part A (TMT-A), Rey Auditory Verbal Learning Test (RAVLT) and Rey-Osterrieth Complex Figure Test (R-OCFT). Those evaluations were performed in which subjects wore their old dentures (OD) or newly fabricated dentures (ND).
Results: We compared ND condition with OD condition. The masseter muscle activity significantly increased in ND condition (p < 0.05, Wilcoxon signed rank test). The brain activity increased significantly in the superior frontal gyrus, precentral gyrus, putamen, inferior parietal lobule, cerebellum, inferior frontal lobe, and middle frontal gyrus under the ND condition than under the OD condition (p < 0.01, uncorrected, cluster size > 10 voxels). Results of TMT-A, RAVLT, and R-OCFT were also significantly improved (p < 0.05, Wilcoxon signed rank test).
Conclusions: In the edentulous elderly, the brain activity was increased following the improvement of the masseter muscle activity. Consequently, it is possible that the improvement of the masseter muscle activity might influ ence on the attention, verbal skills, and visual memory.
... Accordingly, in humans, chewing quickens cognitive processing (Hirano et al. 2013) and ...
... improves arousal (Allen and Smith 2012;Johnson et al. 2012) and attention (Tucha et al. 2004), leading to an increment of blood perfusion in several cortical and subcortical structures (Hirano et al. 2013). Moreover, chewing can prevent degenerative process in older animals and, possibly, in humans, where it is related to preserved cognitive functions (Moriya et al. 2011), thus prompting its use in the field of neurorehabilitation for contrasting the cognitive decline associated to age-related neurodegenerative processes (Wilson et al. 2010). ...
Trigeminal sensorimotor activity stimulates arousal and cognitive performance, likely through activation of the Locus Coeruleus (LC). In this study we investigated, in normal subjects, the effects of bilateral trigeminal nerve stimulation (TNS) on the LC-dependent P300 wave, elicited by an acoustic oddball paradigm. Pupil size, a proxy of LC activity, and electroencephalographic power changes were also investigated. Before TNS/sham-TNS, pupil size did not correlate with P300 amplitude across subjects. After TNS but not sham-TNS a positive correlation emerged between P300 amplitude and pupil size within frontal and median cortical regions. TNS also reduced P300 amplitude in several cortical areas. In both groups, before and after TNS/sham-TNS, subjects correctly indicated all the target stimuli. We propose that TNS activates LC, increasing the cortical norepinephrine release and the dependence of the P300 upon basal LC activity. Enhancing the signal-to-noise ratio of cortical neurons, norepinephrine may improve the sensory processing, allowing the subject to reach the best discriminative performance with a lower level of neural activation (i.e., a lower P300 amplitude). The study suggests that TNS could be used for improving cognitive performance in patients affected by cognitive disorders or arousal dysfunctions.
... 60,67,123 Functional MRI and position emission topography studies have also reported increased cortical blood flow 124 and activation of the primary sensorimotor cortex, pre-frontal cortex, pre-motor cortex, supplementary motor area, insular cortex, thalamus, cerebellum and hippocampus after mastication. [63][64][65]76,82,125,126 ; which are significantly associated with various cognitive functions, including episodic memory, verbal fluency, psychomotor performance and delayed word recall. 29,82,126 Few studies have investigated the relationship between the rehabilitation of edentulous jaws with implant prostheses and its effect on cortical activity. ...
... [63][64][65]76,82,125,126 ; which are significantly associated with various cognitive functions, including episodic memory, verbal fluency, psychomotor performance and delayed word recall. 29,82,126 Few studies have investigated the relationship between the rehabilitation of edentulous jaws with implant prostheses and its effect on cortical activity. These studies, including our study, reported a gradual increase in brain activity and cognitive scores with the progression of prosthetic rehabilitation. ...
Background:
The implications of oral rehabilitation after tooth loss requires further investigation.
Objectives:
To conduct a pilot study to investigate: i) changes in masticatory performance with progressive oral implant rehabilitation (POR); ii) association between POR and neurocognitive function using functional magnetic resonance imaging (fMRI); and (iii) oral health-related quality of life (OHQoL) outcomes.
Methods:
Four completely edentulous patients (mean age: 73±1.4 years) participated. Each received new complete removable dental prostheses (RDPs) transitioned to mandibular two implant-retained RDPs (IR-RDP). Assessments were performed at 4 time points for neurocognitive skills, fMRI with functional tasks (jaw clenching, working memory and sustained attention, inhibition), masticatory performance with colour-changing gum and OHQoL. Assessments were performed with new complete RDPs (T0 as baseline data) and IR-RDPs at 1 week (T1), 6 weeks (T2) and 12 months (T3) post-insertion. Data analyses were based on intra-patient and inter-patient results.
Results:
Masticatory performance and QoL improved with an IR-RDP at each time point. FMRI jaw clenching sensory and motor cortical activity decreased at T1, with motor cortical activity increasing to T0 levels at T2. For cognitive fMRI activation tasks, cortical activity decreased from T0 to T1 across all regions of interests (ROI), and increased at T2 throughout the cognitive brain regions. Neurocognitive skills declined at T1, followed by improvement to or beyond T0 levels at T2.
Conclusion:
Improvements in masticatory performance and OHQoL occurred from complete RDPs to IR-RDP. Prosthetic adaptation was associated with neurocognitive changes to pre-insertion activity levels or greater after 6 weeks. This pilot data suggests both behavioural and neural associations between POR and cognition, however, larger study numbers are required.
... Chewing also improves masticatory function by increasing the mass of the masticatory muscles [10]. In addition, previous studies [11][12][13][14] suggest that chewing positively influences cerebral blood flow, alleviates stress, and regulates cognitive function. Overall, chewing is thought to be a favorable masticatory behavior. ...
Background: Consuming a variety of foods is believed to promote thorough chewing; however, it remains unclear whether individuals who consume various foods actually chew them thoroughly. Therefore, this study aimed to examine the association between dietary variety and masticatory behaviors, measured using wearable devices, among community-dwelling older adults. Methods: Participants were from the Itabashi Longitudinal Study of Aging, meeting the eligibility criteria, including the ability to exchange messages via smartphone or computer. Masticatory behaviors (number of chews, chewing duration, and speed) and meal photo data were objectively measured using an ear-worn bite sensor and its application for two or three meals per day for at least three days at home. The “modified Dietary Variety Score (m-DVS)” (range 0–10, with higher values indicating greater dietary variety) was calculated by registered dietitians. Generalized linear mixed models assessed the association between m-DVS as the exposure variable and masticatory behaviors as the outcome variable. Covariates included sociodemographic status, health behavior, health status, oral health, and oral function. Results: Five hundred and eighty-seven mealtime data entries from 63 participants were included in the analysis. The m-DVS was significantly positively associated with the number of chews (cycles, unstandardized regression coefficient = 116.5, 95% confidence interval [CI] = 85.2 to 147.8) and chewing duration (min, unstandardized regression coefficient = 1.7, 95% CI = 1.3 to 2.2). Conclusions: Consuming more varied food groups was associated with more chews and longer chewing duration among community-dwelling older adults, potentially promoting thorough chewing.
... The preservation of mechanoreceptors in the periodontium and alveolar bone is a significant predictor of the preservation of masticatory abilities of chewing muscles (Brodin et al. 1993;Türker et al. 2007). Preserving masticatory abilities is essential for fast and appropriate cognitive reactions and responses (Hirano et al. 2012), with mastication reducing latencies of relevant potentials related to external stimuli and increasing vigilance (Sakamoto et al. 2015). The entry of the trigeminal nerve into the brain around the pons Varoli has both acute and long-lasting effects on the brain and its cognitive functions. ...
Our review study addresses the issue of tooth loss, which is caused by loss of masticatory function and its impact on cognitive functions, dementia, and Alzheimer's disease. Numerous studies have confirmed a positive correlation between premature tooth loss, reduction in masticatory function and significant cognitive decline observed through learning disabilities, including overcoming ordinary life problems to early and advanced forms of dementia. Reduced numbers of teeth in the main food processing area, i.e., loss of large molars, have been implicated as a possible cause of cognitive impairment. In research in this area, some groups of major etiopathogenetic causes of this issue have also been established. A significant etiopathogenetic cause of tooth loss is the disappearance of their mechanoreceptors in the periodontium, causing the disappearance of sensorimotor excitation via the cranial nerve V and the associated atrophic changes in the trigeminal brain nuclei and their branching in the Locus Coeruleus area. It may cause further neurodegenerative involvement in this area, one of the centers of the adrenergic system involved in cognitive function. Relatively well-studied factors are the lack of blood supply to the cerebral area during inadequate mastication caused by loss of molars and the consequent hypoxia of brain and nerve structures. In the research and development of Alzheimer's disease, there have been many recent references to the fact that the primary bacterium causing periodontitis, Porphyromonas gingivalis, can infect the neurons of the cranial nerve V ending close to the Locus Coeruleus and thus tau proteins, after tooth extractions, can spread to other subcortical nuclei in the brain. These findings are of great relevance to clinical practice in dentistry as we strive to prevent tooth loss in the distal compartment, which is made possible by the tremendous expansion of endodontic techniques and technologies to save de facto every tooth and its periodontium with the mechanoreceptors necessary to preserve sensorimotor nerve excitability and sensorimotor nerve networks. We uncompromisingly eliminate every periodontal infection in the subgingival region as part of our preventive-therapeutical procedures.
... Although alternative input methods such as voice recognition are feasible, buttons were selected due to their operational simplicity. Buttons have been used in research on care robots [12] and found to be usable with sufficient response speed even by the elderly [39][40][41]. This article has been accepted for publication in IEEE Access. ...
The rising aging population has escalated the need for physically assistive robots to aid the elderly, potentially taking over some roles of caregivers. However, a general unease exists among people when they physically interact with autonomously operating robots, leading to their limited adoption. To address this issue, accountability has been studied to reduce anxiety by displaying robot information. However, the one-way information presentation leaves the user feeling anxious because the content and timing of the movements might be inconsistent with the user’s intentions. Therefore, the importance of mutual communication in care robots was validated in this study using a user interface simple enough for the elderly to use during daily activities. A care robot was equipped with a screen and speaker for information presentation and user-operable buttons for intention input, enabling two-way communication. The robot presents its movement options to the user for confirmation when the robot detects user abnormality, followed by the user conveying the desired intention to the robot. The effectiveness of this mutual communication approach was rigorously tested under various conditions. The results of questionnaires indicated that the inclusion of button input for mutual communication enhanced user comfort and ease of use, underpinning the importance of bidirectional interaction in physically assistive robotics.
... Furthermore, 45 min of acute highintensity resistance exercise reduced behavioral performance on the Stroop task but increased RT, whereas 180 min of moderateintensity exercise improved behavioral performance on the Simon task and cognitive EF (Brush et al., 2016). Most reports have shown that acute moderate-intensity resistance exercise can cause cognitive function decline (Hirano et al., 2013;Russell et al., 2021;Engeroff et al., 2022). Consistent with the literature, this research found that the 1,500 m freestyle at maximal speed led to a decrease in cognitive function; IC in the Stroop task, SGT, and TMT were reduced, and serum 5-HT increased, which is possibly due to central fatigue and cognitive decline, affecting the effective contraction of skeletal muscle (Kieran et al., 2018;Zhai et al., 2018). ...
Introduction
Physical exercise can improve cognitive function, and the degree of impact on cognitive function is related to exercise modality, intensity, and duration. However, few studies have been conducted on the effects of competitive sports on cognitive function. The 1,500 m freestyle is the longest pool-based swimming event in the Olympic Games. This study explores the effects of 1,500 m freestyle at maximal speed on athletes’ cognitive function and analyzes the potential mechanism of cognitive function reduction in freestyle at maximal speed from the perspective of hemoglobin oxygenation difference (Hbdiff).
Methods
A total of 13 male university swimmers were required to take part in a 1,500 m freestyle competition, swimming at maximal speed. The relevant indicators, including cognitive function and freestyle at maximal speed, before and after the competition were tested and analyzed. Cognitive function was assessed using the Schulte grid test (SGT), the trail-making test (TMT), and the digit span test (DST). The neurobiological characteristics of cognitive function, such as the prefrontal cortex (PFC), response time (RT), and accuracy rate (ACC), were tested using functional near-infrared spectroscopy (fNIRS).
Results
A significant decrease in scores for SGT, TMT, and digit span test-backward (DST-B) (p < 0.01). Oxygenated hemoglobin (Oxy-Hb) concentrations in the right frontopolar area (R-FPA) of brain channels 8 (p < 0.01) and 9 (CH8, 9) (p < 0.05), the right dorsolateral prefrontal cortex (R-DLPFC) CH10 (p < 0.05), and the middle dorsolateral prefrontal cortex (M-DLPFC) CH18 (p < 0.01) were significantly altered, and the right area of the brain was activated. The total Oxy-Hb concentrations in the regions of interest (ROIs) of R-FPA, R-DLFPC, and M-DLFPC were changed significantly (p < 0.01).
Discussion
The exhaustive performance of a 1,500 m freestyle event resulted in both physical fatigue and a decline in cognitive function. This decline may be attributed to the activation of specific regions of interest, namely the FPA, DLPFC, and M-DLPFC, within the prefrontal cortex (PFC), as well as alterations in functional connectivity.
... Emergent evidence on the effects of chewing on increased attention, memory, and cognitive processing shows that the masticatory condition is related to cognitive function. [26,[29][30][31][32][33][34][35]. ...
Masticatory function such as chewing is expected to modify human cognitive function, and/or the possibility of improving cognitive function is also predicted. This systematic review investigated whether masticatory function affects cognitive function for older/young adults. Full articles written in English from January 2000 to April 2022 were collected using PubMed and Cochrane Library. Target outcomes were cognitive function test scores, cognitive processing speed (reaction time), and masticatory function. For each research question, two independent reviewers conducted the search and screening, data extraction, quality assessment, and risk of bias assessment. The reviewers resolved any disagreements by discussion. From 226 articles retrieved, 20 were included in this review. Older adults with lower scores on the cognitive function test had lower masticatory performance, lower chewing ability, chewing difficulty, and decreased number of teeth. An increased risk of cognitive impairment was found in older adults with masticatory dysfunction. For young adults, gum chewing significantly reduced the processing speed of cognitive tasks compared to no gum chewing. Although most of the evidence included had a low level of evidence and a high risk of bias because of the research designs, the results still suggest that mastication may be a factor in improving cognitive function.
... on cognitive function [9][10][11]. ...
Purpose: Individuals with impaired masticatory function tend to prefer soft foods, which results in decreased masticatory muscle activity. This study examined the association between the oral condition (number of teeth, occlusal force, and occlusal contact area) and dietary hardness using a daily dietary questionnaire.
Methods: This cross-sectional study evaluated 1841 participants aged 69–71 and 79–81 years. Registered dentists examined the number of teeth, occlusal force, and occlusal contact area. Dietary hardness was defined as the estimated masticatory muscle activity required for a habitual diet. Habitual diet during the preceding month was assessed using a brief self-administered diet history questionnaire. Confounding factors, such as age, sex, socioeconomic status, smoking habits, history of chronic diseases (hypertension, hyperlipidemia, and diabetes), and cognitive function were also evaluated. Multivariate linear regression analyses were performed to assess the association between dietary hardness and each oral condition.
Results: Occlusal force (standardized regression coefficients [β]=0.08, P < 0.01) and occlusal contact area (β=0.06, P < 0.01) were significantly associated with dietary hardness after adjusting for the confounding factors. Number of teeth was not significantly associated with dietary hardness. In addition, the associations between dietary hardness, sex, and a history of diabetes were stronger than those between dietary hardness and oral factors.
Conclusions: Occlusal force and contact area were significantly associated with dietary hardness as estimated from the masticatory muscle activity using a daily diet questionnaire.
... The previous studies reported an effect of mastication on cognitive tests related to arousal (Nageishi et al., 1993), shortened reaction time (Chu, 1994), and working memory (Baker et al., 2004;Stephens & Tunney, 2004;Wilkinson et al., 2002). Furthermore, functional magnetic resonance imaging (fMRI) studies have revealed increased brain activity in specific regions during mastication, including the prefrontal cortex, anterior cingulate cortex, and left frontal gyrus during mastication (Higaki et al., 2016;Hirano et al., 2013). ...
Mastication leads to an immediate enhancement in cognitive functions, including inhibitory control. Furthermore, the hardness of the food increases sympathetic nerve activity during and immediately after mastication. Hence, the cognitive function could be enhanced by increased sympathetic nerve activity. The present study aimed to investigate the effects of food hardness on cognitive inhibitory control function in humans. The participants were 23 healthy adults (19-22 years old). Experiments were conducted with two types of gummies (soft and hard). The participants ingested 13 g of gummies and performed a stop-signal task to measure cognitive inhibitory control function after they rested for 5 min. The reaction time for the stop-signal task after gummy consumption was significantly shorter in the hard gummy condition compared to the soft gummy condition (p < .05). Furthermore, the accuracy rate of the responses was also significantly higher in the hard gummy condition compared to the soft gummy condition (p < .05). The results of the present study suggest that food hardness enhances cognitive inhibitory control function in humans.
... The results of the UKT in the present study showed no effect of a 90-min nap plus a 30-min nap on early morning computational performance. The UKT is used to measure cognitive task performance, and involves mental arithmetic and handwriting 30 . It is possible that a 90-min nap may be more effective than a 30-min nap for complex task performance. ...
The aim of this study was to investigate alertness and cognitive performance immediately after and until the end of the night shift after taking a 120-min monophasic nap (One-nap) or a split 90-min and 30-min nap (Two-nap) during a 16-h simulated night shift, and the relationship between sleep quality and both alertness and performance. This study was performed in 41 females. Among them, 15 participants were included in the No-nap group, 14 in the One-nap group (22:00–00:00), and 12 in the Two-nap group (22:30–00:00 and 02:30–03:00). Participants were tested every hour from 16:00 to 09:00 for performance on the Uchida-Kraepelin test, as well as for subjective feelings of fatigue and drowsiness, body temperature, and heart rate variability. The shorter the sleep latency, the worse the alertness immediately after the 90-min nap. The 120-min and 30-min naps also revealed that prolonged total sleep time led to increased fatigue and drowsiness upon awakening. From 04:00 to 09:00, in the No-nap and One-nap groups, fatigue was higher than in the Two-nap group. The One-nap and Two-nap groups did not show improved morning performance. These results suggest that a split nap might improve drowsiness and fatigue during a long night shift.
... The impact of chewing on maxillofacial development, stomatognathic system balance, and central motor control are extensively documented in the literature [11,12]. Several experimental and epidemiological studies have investigated the relationship between chewing function and cognitive status or cerebral activation [13][14][15][16]. In particular human experimental studies have shown that short-term use of chewing gum results in increased regional cerebral blood flow and enhancement of cognitive function, such as working memory [15,16]. ...
Food hardness is one of the dietary features that may impact brain functions. We performed a systematic review to evaluate the effect of food hardness (hard food versus soft food diet) on behavior, cognition, and brain activation in animals and humans (PROSPERO ID: CRD42021254204). The search was conducted on 29 June 2022 using Medline (Ovid), Embase, and Web of Science databases. Data were extracted, tabulated by food hardness as an intervention, and summarized by qualitative synthesis. The SYRCLE and JBI tools were used to assess the risk of bias (RoB) of individual studies. Of the 5427 studies identified, 18 animal studies and 6 human studies met the inclusion criteria and were included. The RoB assessment indicated that 61% of animal studies had unclear risks, 11% had moderate risks, and 28% had low risks. All human studies were deemed to have a low risk of bias. The majority (48%) of the animal studies showed that a hard food diet improved behavioral task performance compared to soft food diets (8%). However, 44% of studies also showed no differential effects of food hardness on behavioral tests. It was also evident that certain regions of the brain were activated in response to changes in food hardness in humans, with a positive association between chewing hard food, cognition performance, and brain function. However, variations in the methodologies of the included studies hindered the meta-analysis execution. In conclusion, our findings highlight the beneficial effects of dietary food hardness on behavior, cognition, and brain function in both animals and humans, however, this effect may depend on several factors that require further understanding of the causality.
... While there were no major differences in behaviors such as warning or collision, short-term chewing alone was able to increase exercise speed and accuracy, in addition to blood oxygen levels, demonstrating that oral function can control cognitive and physical functions. [29] In the present study, the OR for cognitive impairment was about 1.28 times as high in people with poor chewing function than in those with good chewing function (Model I). In Model II, which identified changes in chewing function from the first wave to the last wave (sixth wave), ORs were 2.21 (95% CI = 1.90-2.58) in the good-poor group and 2.11 (95% CI = 1.74-2.55) in the poor-poor group. ...
A growing body of literature suggests that oral health can influence cognitive function during aging. However, it is currently unclear whether reduced masticatory efficiency influences cognitive impairment in longitudinal studies.
This study sought to investigate the effects of reduced chewing ability on the incidence of cognitive impairment using national representative data from 10 years of follow-up in Korea. Among the 10,254 people recruited in 2006 (1st wave), 7568 with normal cognitive function were selected. The participants were followed up every 2 years. The number of participants followed up until the 6th wave was 5020 in 2016. Chewing ability and scores on the Mini-Mental State Examination were recorded using self-reported questionnaires. Risk factors for dementia taken from systematic literature reviews were used as covariates. We performed logistic regression and created general estimating equation models after controlling for all covariates to assess the relationship between chewing ability and cognitive decline. Decreased chewing function was associated with mild cognitive impairment after controlling for confounding variables.
The odds ratio for cognitive impairment was about 1.28 times higher than in people with poor chewing function as in those with good chewing function. We identified changes in chewing function from the 1st wave to the 6th wave; the odds ratios were 2.21 (95% confidence interval = 1.90–2.58) in the good-poor group and 2.11 (95% confidence interval = 1.74–2.55) in the poor-poor group.
We identified an impairment in cognitive function in the poor (poor-poor and good-poor) chewing ability group. Therefore, we have confirmed that reduced mastication efficiency may contribute to a deterioration in cognitive function. People with deteriorated chewing ability must be given additional attention to aid in the prevention of cognitive decline.
... Recent investigations have shown how chewing can exert a stimulating effect on cognitive performance. Gum chewing enhances alertness and attention (Tucha et al., 2004;Allen and Smith, 2012;Johnson et al., 2012), speed of neural processing (Hirano et al., 2013), learning and memory (Allen et al., 2008;Smith, 2009). Shortening of reaction times and latencies of stimulus-triggered evoked potentials are also observed (Sakamoto et al., 2009;Hirano and Onozuka, 2014). ...
Chewing improves cognitive performance, which is impaired in subjects showing an asymmetry in electromyographic (EMG) masseter activity during clenching. In these subjects, the simultaneous presence of an asymmetry in pupil size (anisocoria) at rest indicates an imbalance in Ascending Reticular Activating System (ARAS) influencing arousal and pupil size. The aim of the present study was to verify whether a trigeminal EMG asymmetry may bias the stimulating effect of chewing on cognition. Cognitive performance and pupil size at rest were recorded before and after 1 min of unilateral chewing in 20 subjects with anisocoria, showing an EMG asymmetry during clenching. Unilateral chewing stimulated performance mainly when it occurred on the side of lower EMG activity (and smaller pupil size). Following chewing on the hypotonic side, changes in cognitive performance were negatively and positively correlated with those in anisocoria and pupil size, respectively. We propose that, following chewing on the hypotonic side, the arousing effects of trigeminal stimulation on performance are enhanced by a rebalancing of ARAS structures. At variance, following chewing on the hypertonic side, the arousing effect of trigeminal stimulation could be partially or completely prevented by the simultaneous increase in ARAS imbalance.
... It includes, among others, cardiovascular diseases and hypertension and stroke, diseases of the stomach, duodenum, kidneys and pancreas, rheumatoid arthritis, neoplastic lesions of the oesophagus and upper gastrointestinal tract and other neoplasms, diabetes, and complications during pregnancy. The range of neurological diseases, mood disorders, obstructive sleep apnea, cervical spine pain, migraine and headaches, hippocampal lesions, memory impairment and general dementia, are considerable [129][130][131][132][133]. These numerous diseases affect many people and have a strong impact on the employment situation in the labor markets, the organization of health care and social security systems in many countries. ...
This paper is a literature review with additional virtual analyses of the authors’ own experimental research results. Knowledge from various areas was synergistically combined, appropriately for concurrent engineering, presenting several possible methodological approaches used in research, optimizing the selection of engineering materials and the conditions of their application with particular application in endodontics. Particular attention was paid to the theoretical aspects of filling material strengths, weaknesses, opportunities, and threats SWOT analysis. Attention was paid to the original concepts of Sustainable Dentistry Development in conjunction with Dentistry 4.0, which includes endodontics as an important element. The dentists’ actions, among others, in conservative dentistry, along with endodontics, requires close cooperation with engineers and the enginering sciences. Methods of root canal preparation were described, together with selected tools, including those made of nitinol. Principles concerning the process of cleaning and shaping the pulp complex are presented. The importance of obturation methods, including the Thermo-Hydraulic-Condensation THC technique, and the selection of filling materials with the necessary sealants for the success of endodontic treatment are discussed. The experimental studies were carried out in vitro on human teeth removed for medical reasons, except for caries, for which two groups of 16 teeth were separated. After the root canal was prepared, it was filled with studs and pellets of a filling material based on polyester materials, which has gained the common trade name of resilon or, less frequently, RealSeal (SybronEndo) with an epiphany sealant. The teeth for the first group were obturated by cold lateral condensation. In the second case the obturation was performed using the Thermo-Hydraulic-Condensation technique using System B and Obtura III. The experimental leakage testing was done using a scanning electron microscope SEM and a light stereoscopic microscope LSM, as typical research tools used in materialography. The research results, in a confrontation with the data taken from the literature studies, do not indicate the domination of resilon in endodontics.
... Mastication and deglutition are essential for dietary intake. Mastication influences not only nutritional status but also oral health-related quality of life (OHRQoL) [6,7] and cognitive function [8][9][10]. Objective assessment of masticatory function (masticatory performance [MP] or masticatory efficiency) has been widely used to evaluate the treatment effect [6,7,[9][10][11][12][13][14][15][16][17][18]. ...
Purpose:
To evaluate masticatory performance (MP), maximum occlusal force (MOF), maximum tongue pressure (MTP) and oral diadochokinesis (ODK) among community-dwelling elderly patients without posterior occlusal support.
Methods:
This study enrolled community-dwelling elderly patients (≥65 years old) who belonged to Eichner A, B4, C1, C2, and C3. Each oral function was statistically compared among groups. Correlations between MP and other variables were examined in Eichner B4 and C patients.
Results:
MP and MOF values in Eichner B4 and C patients were significantly lower than in Eichner A patients. There were significant differences in MTP values between Eichner "A and C2, C3", and "B4 and C2, C3". ODK in Eichner C patients showed significantly lower values compared to Eichner A patients in general. Although there were statistically significant correlations of MP with age, the number of remaining teeth and all oral functions were identified, and multiple regression analysis indicated that MOF and MTP were independently related to MP.
Conclusion:
Oral functions in Eichner B4 and C patients were lower compared to Eichner A patients. MP was significantly correlated with MOF and MTP in elderly patients without posterior occlusal support, suggesting the importance of rehabilitation of MOF and MTP in MP.
... The load generated by mastication effects the maxillary bones growth maintaining the patency and viscoelasticity of the cranial sutures during aging (Sun, Lee, & Herring, 2007;Herring, 2008;Rice, 2008;Sun, Lee, & Herring, 2004) and the mandibular growth acting on the development of the condyle and changes in the thickness of the cartilage (Hinton, 2014;Hinton, Jing, & Feng, 2015;Ishida, Yabushita, & Ono, 2013;Radke, Kull, & Sethi, 2014). Further mastication seems to have considerable effects on general health problems in adults such as dementia (Tada & Miura, 2017) and obesity (Tada & Miura, 2018) and during developmental age such as impaired spatial memory and learning function (Fukushima-Nakayama', Ono, & Hayashi, 2017;Hirano et al., 2013;Masood, Masood, & Newton, 2014). ...
... The global dental consumables market, which also applies to endodontics to some extent, in 2016 reached USD 38.921 million, while it is forecasted to reach USD 55.584 million in 2023, with a CAGR of 5.2% [128] ( Figure 3). The treatment is based on caries, as the most common infectious disease in the world, affecting 3-5 billion people [1], causing many systemic diseases [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], as well as personality changes leading to dementia [29][30][31][32][33][34][35], and if necessary the necessity to extract teeth, causing toothlessness, which may also cause many systemic complications [8][9][10][11][12][13]. However, it should be emphasized that dentists treat tooth extraction as a necessity in the event of failure to continue endodontic treatment [103,104], performed carefully to avoid complications due to iatrogenic causes [53][54][55][56][57][58]. ...
The importance of endodontics is presented within our own concept of Dentistry Sustainable Development (DSD) consisting of three inseparable elements; i.e., Advanced Interventionist Dentistry 4.0 (AID 4.0), Global Dental Prevention (GDP), and the Dentistry Safety System (DSS) as a polemic, with the hypothesis of the need to abandon interventionist dentistry in favour of the domination of dental prevention. In view of the numerous systemic complications of caries that affect 3−5 billion people globally, endodontic treatment effectively counteracts them. Regardless of this, the prevention of oral diseases should be developed very widely, and in many countries dental care should reach the poorest sections of society. The materials and methods of clinical management in endodontic procedures are characterized. The progress in the field of filling materials and techniques for the development and obturation of root canals is presented. The endodontics market is forecast to reach USD 2.1 billion in 2026, with a CAGR of 4.1%. The most widely used and recognized material for filling root canals is gutta-percha, recognized as the “gold standard”. An alternative is a synthetic thermoplastic filler material based on polyester materials, known mainly under the trade name Resilon. There are still sceptical opinions about the need to replace gutta-percha with this synthetic material, and many dentists still believe that this material cannot compete with gutta-percha. The results of studies carried out so far do not allow for the formulation of a substantively and ethically unambiguous view that gutta-percha should be replaced with another material. There is still insufficient clinical evidence to formulate firm opinions in this regard. In essence, materials and technologies used in endodontics do not differ from other groups of materials, which justifies using material engineering methodology for their research. Therefore, a detailed methodological approach is presented to objectify the assessment of endodontic treatment. Theoretical analysis was carried out using the methods of procedural benchmarking and comparative analysis with the use of contextual matrices to virtually optimize the selection of materials, techniques for the development and obturation of root canals, and methods for assessing the effectiveness of filling, which methods are usually used, e.g., in management science, and especially in foresight research as part of knowledge management. The results of these analyses are presented in the form of appropriate context matrices. The full usefulness of the research on the effectiveness and tightness of root canal filling using scanning electron microscopy is indicated. The analysis results are a practical application of the so-called “digital twins” approach concerning the virtual comparative analysis of biomaterials used in endodontic treatment.
... Bae and Park [42] reported that denture-wearers had decreased neck muscle strength than those without dentures, which may cause the body to bend forward. Moreover, previous studies reported that masticatory function may affect cognitive processing speed [43], physical reaction time [44], and cerebral blood oxygen-dependent signal [45]. Other studies have reported that the restoration of masticatory function can improve arousal and modulate cognitive functions [46]. ...
While appropriate nutrient intake is important for older adults, various oral problems cause decreased masticatory function. This cross-sectional study aimed to identify the factors associated with decreased masticatory performance in older adults. Oral examinations were performed on 80 participants (mean age: 75.10 ± 5.64 years) to determine the number of functional tooth units (FTUs). Symptoms of periodontal and temporomandibular diseases were evaluated via a questionnaire. The tone, elasticity, and dynamic stiffness of the masseter muscle were measured using the Myoton® PRO device. The mixing ability test was used to assess the masticatory performance, and the mixing ability index (MAI) was calculated. The analysis of covariance test was performed to adjust for confounding factors, and multiple logistic regression analysis was performed to identify the risk factors affecting MAI. A lower MAI was significantly associated with higher tone (p = 0.006) and lower elasticity (p = 0.013). The number of FTUs (adjusted odds ratio (OR) = 0.724, p = 0.029), tone (adjusted OR = 1.215, p = 0.016), and elasticity (adjusted OR = 4.789, p = 0.038) were independently associated with the MAI. Muscle function training and prosthetic treatments may help increase masticatory performance in older adults, which would improve overall health.
... Bae and Park [42] reported that denture-wearers had decreased neck muscle strength than those without dentures, which may cause the body to bend forward. Moreover, previous studies reported that masticatory function may affect cognitive processing speed [43], physical reaction time [44], and cerebral blood oxygen-dependent signal [45]. Other studies have reported that the restoration of masticatory function can improve arousal and modulate cognitive functions [46]. ...
While appropriate nutrient intake is important for older adults, various oral problems cause de-creased masticatory function. This cross-sectional study aimed to identify the factors associated with decreased masticatory performance in older adults. Oral examinations were performed on 80 participants (mean age: 75.10 ± 5.64 years) to determine the number of functional tooth units (FTUs). Symptoms of periodontal and temporomandibular diseases were evaluated via a ques-tionnaire. The tone, elasticity, and dynamic stiffness of the masseter muscle were measured using the Myoton® PRO device. The mixing ability test was used to assess the masticatory performance and the mixing ability index (MAI) was calculated. The analysis of covariance test was performed to adjust for confounding factors and multiple logistic regression analysis was performed to identify the risk factors affecting MAI. A lower MAI was significantly associated with higher tone (p = 0.006) and lower elasticity (p = 0.013). The number of FTUs (adjusted odds ratio [OR] = 0.724, p = 0.029), tone (adjusted OR = 1.215, p = 0.016), and elasticity (adjusted OR = 4.789, p = 0.038) were independently associated with the MAI. Muscle function training and prosthetic treatments may help increase masticatory performance in older adults, which will improve overall health.
... Rising evidence on the effects of chewing in increased attention, memory, and cognitive processing demonstrates that masticatory condition has a link to cognitive health [19]. Since exosomes can translocate from muscle cells to nerve cells as cargo vehicles, our hypothetic mechanism for connecting mastication and cognitive health is that muscle activity can directly affect amyloid β burden. ...
Cognitive health is subject to decline with increasing numbers of lost teeth which impacts mastication. This study is a descriptive data analysis of the association between masticatory and cognitive conditions using a large database. We obtained the dental and medical records from Japan's universal healthcare system (UHCS) from the national database in 2017. The data from 94% of the Japanese population aged 65 and over is included. It is inclusive of diagnostic codes for various types of cognitive impairment, as well as dental treatment records from 2012 to 2017. The cognitive impairment group was compared to those without a diagnosis of cognitive impairment. Crude odds ratio between loss of mastication with natural teeth (exposure) and cognitive impairments (outcome) were compared. Patients who have lost masticatory function are likely to have cognitive impairment with an odds ratio of 1.89 (p<0.0001) for early elderly (aged 65-75) and 1.33 (p<0.0001) for advanced elderly (over 75). Patients who are edentulous and function with complete dentures are likely to have cognitive impairment with an odds ratio of 2.38 (p<0.0001) and 1.38 (p<0.0001), respectively. The data shows a convincing and significant result of an association between cognitive health and oral health, related to masticatory conditions.
... A study of cerebral blood flow responses while fatigued found that the blood flow response decreased in associated areas of the visual cortex [23]. Conversely, the increased cerebral blood flow, as a result of chewing gum, has been suggested to help increase alertness or at least attenuate reductions in alertness [24,25]. Regarding the findings related to relaxation caused by odor and/or taste, rather than mastication, we used samples with the same odors and tastes. ...
Purpose. To investigate the effects of chewing gum and tablet candy to reduce eyestrain in healthy individuals. Materials and Methods. A double-blinded crossover trial was conducted. Forty-six healthy individuals (23 men, 23 women) between 20 and 59 years old, feeling eyestrain, were enrolled. Each 10-year age group included 12 individuals except the 30s group, which included 10 individuals. A visual task was performed on reading material displayed on a computer screen at a fixed distance for 60 min. Gum or tablet candy of two pieces were chewed for two 15-min periods starting 15 and 45 min after starting to read. Subjects chewed gum on Day 1 and tablet candy on Day 2, and vice versa. Primary outcome is as follows: subjective eye fatigue (eye tiredness, eye heaviness, blurred vision, double vision, and eye dryness) using a visual analog scale (VAS). Secondary outcomes are as follows: subjective accommodation from near and far points of accommodation measured with a D’ACOMO, spherical equivalent refraction, and eye dryness by analyzing ring break-up time (RBUT) measured with the RT-7000 Auto Ref-Topographer. Results. The VAS scores of subjective eye fatigue were not significantly changed between chewing gum and tablet candy (P=0.397-P=0.909). Those scores of eye tiredness and eye heaviness were significantly longer before and after the visual task with tablet candy (P=0.013 and P=0.025, respectively) but not with chewing gum. The changes of subjective accommodation were significantly lower after the visual task between chewing gum and candy (P=0.043). There were significant differences among each age group (20 s vs. 30 s, P=0.594; 20 s vs. 40 s, P=0.002; 20 s vs. 50 s, P=0.002). After reading, the changes of spherical equivalent refraction did not indicate a shift toward myopia (P=0.267). In the RBUT, there were no significant differences between the samples (P=0.680). Conclusions. Chewing gum helps improve the ability of the eye to focus, especially in young adults.
... The load generated by mastication effects the maxillary bones growth maintaining the patency and viscoelasticity of the cranial sutures during aging (Sun, Lee, & Herring, 2007;Herring, 2008;Rice, 2008;Sun, Lee, & Herring, 2004) and the mandibular growth acting on the development of the condyle and changes in the thickness of the cartilage (Hinton, 2014;Hinton, Jing, & Feng, 2015;Ishida, Yabushita, & Ono, 2013;Radke, Kull, & Sethi, 2014). Further mastication seems to have considerable effects on general health problems in adults such as dementia (Tada & Miura, 2017) and obesity (Tada & Miura, 2018) and during developmental age such as impaired spatial memory and learning function (Fukushima-Nakayama', Ono, & Hayashi, 2017;Hirano et al., 2013;Masood, Masood, & Newton, 2014). ...
Objective
This systematic review had the purpose to collect existing data concerning the influence of food hardness on mastication in adults.
Design
The review was listed with PROSPERO (CRD42017069760) and was directed following with PRISMA and CRD (Centre for Reviews and Dissemination, University of York) statement. A database search of articles issued from 1998 up to December 2018 was carried-out using four databases: Pubmed, Cochrane Library, Web of Science and Scopus. The lists of references of the articles selected for the review were read to identify any other relevant studies. The included publications were analysed for level of evidence, study design, sample characteristics, test of mastication, primary outcomes and key results. A quality assessment of the articles included in the review was performed.
Results
1686 articles were found through database searching. The studies that complied with all the inclusion criteria and were considered for the conclusive analysis were 38 and their methodological quality was scored as moderate/low. The findings of the analysed articles were consistent, despite the presence of different methodologies and the lack of a complete control of the bias. They revealed that the majority of the chewing parameters, which were gathered in four groups: 1) number of cycles, 2) sequence duration, 3) muscle activity and 4) coordination and amplitudes and shape of mandibular displacements, increased in the transition from soft to hard food.
Conclusions
Hard-diet in adults has an impact on the masticatory function increasing almost all the physiological masticatory parameters, muscle coordination and changes of masticatory side.
... Toothlessness is often the direct cause of shortening human life. Chewing dysfunction causes morphological and functional changes in the hippocampus while chewing helps to maintain the proper functions of the hippocampus [51][52][53][54][55][56][57]. V. ...
The general goals of advanced digitized production in the Industry 4.0 stage of the industrial revolution were presented along with the extended holistic model of Industry 4.0, introduced by the authors, indicating the importance of material design and the selection of appropriate manufacturing technology. The effect of the global lockdown caused by the SARS-CoV-2 virus transmission pandemic was a drastic decrease in production, resulting in a significant decrease in the gross domestic product GDP in all countries, and gigantic problems in health care, including dentistry. Dentists belong to the highest risk group because the doctor works in the patient’s respiratory tract. This paper presents a breakthrough authors solution, implemented by the active SPEC strategy, and aims to eliminate clinical aerosol at the source by negative pressure aspirating bioaerosol at the patient’s mouth line. The comparative benchmarking analysis and its results show that only the proprietary solution with a set of devices eliminates the threat at the source, while the remaining known methods do not meet the expectations. The details of this solution are described. Photopolymer materials and additive Digital Light Printing (DLP) technology were used.
Background:
A decline in masticatory function may indicate brain dysfunction related to dementia, but the relationship between masticatory function and dementia risk remains unclear. This study aimed to investigate whether masticatory function is associated with the risk of cognitive decline and dementia.
Methods:
Data were obtained from the nationwide prospective cohort study of randomly sampled community-dwelling Koreans aged ≥ 60 years. The 5,064 non-demented participants, whose number of chewing cycles per bite was assessed by clinical interview, were followed for 8 years with biennial assessments of cognitive performance and clinical diagnoses of all-cause dementia and Alzheimer's disease (AD). Structural brain magnetic resonance imaging was collected from a subset of cohort participants and their spouses for imaging analyses.
Results:
Males who chewed ≥ 30 cycles/bite had faster decline in global cognition and memory function and were at higher risk for incident all-cause dementia (hazard ratio [HR], 2.91; 95% confidence interval [CI], 1.18-7.18) and AD (HR, 3.22; 95% CI, 1.14-9.11) compared to males with less than 10 cycles/bite. Additionally, increased chewing cycles in males were associated with reduced brain volume, particularly in regions involved in compensatory cognitive control of mastication. There was no significant association between chewing cycles and the risk of dementia or brain volume in females.
Conclusion:
Older men who frequently chew their meals could be considered a notable population at risk for dementia who should be carefully assessed for their cognitive trajectories.
Objectives:
Chewing gum has been shown to improve aspects of cognition and mood with sustained attention being particularly receptive to the effects of chewing. Chewing gum may also be a useful vehicle for administering functional ingredients. The herbal extract Rhodiola rosea and certain B-vitamins have previously been shown to improve aspects of cognition and subjective state, but their combined effects have not been studied to date.
Methods:
The current randomised, placebo-controlled, double-blind, balanced crossover study compared the effects of a functional gum containing Rhodiola rosea and B-vitamins to flavour-matched regular chewing gum and a flavour-matched placebo. Thirty-six healthy young participants completed measures of attention and mood at baseline, during chewing, and 1-h after chewing.
Results:
Chewing both functional and regular gum was shown to reduce errors on a digit vigilance task compared to placebo irrespective of whether measured during or after chewing. There were no benefits to adding functional ingredients to the gum.
Discussion:
Future chewing research should consider different formats of placebo. Sex differences in response to chewing and the impact of rate and intensity of chewing should also be explored.
Trial registration:
ClinicalTrials.gov identifier: NCT05544500.
Chewing is a simple and effective method for managing psychological stress and maintaining optimal physical and mental health. This study aimed to systematically review the potential benefits and disadvantages of chewing in sports. We conducted a comprehensive literature search for all relevant articles sourced from the Cochrane Central Register of Controlled Trials, MEDLINE, and PUBMED. We used “chewing OR mastication OR masticatory” and “sport OR sports OR training OR exercise OR physical fitness OR athletic OR athlete OR performance.” We adopted a three-step screening process for titles, abstracts, and full-texts to select eligible articles. After applying our inclusion and exclusion criteria, we performed a full-text screening of 101 articles. The results showed that chewing could improve muscle activation, force production, muscle strength, and postural stability, positively affecting sports performance, especially in rugby, judo, kendo, and climbing. The beneficial effects of chewing on sports performance may be associated with the activation of central nervous system circuits, an increase in arousal level and alertness, and improvements in cognitive ability. In contrast, chewing gum poses a potential risk of laryngeal spasm during activities, such as swimming or cricket. Attention should be paid to chewing gum while engaging in sports.
Cognitive functions are important brain functions that enable the acquisition, storage
and use of information. Cognitive functions play an important role in the regulation and
adjustment of swallowing function, as all body functions. Therefore, the characteristics
of the individual, food and environment are perceived and predicted, and swallowing
is carried out safely by adapting to changing conditions. In particular, basic cognitive
functions including visual perception, orientation, attention, memory and executive func-
tions are necessary for effective and safe swallowing. Swallowing function is examined
as pre-swallowing phase, oral preparation, pharyngeal and esophageal phases. Although
cognitive functions are primarily needed in the pre-swallowing phase and oral preparation
phase, different levels of cognitive function are needed in the whole swallowing process.
The relationship between cognitive disorders and swallowing disorders is clearly seen
in conditions such as Alzheimer’s, dementia and stroke where cognitive functions are
affected. There is a need for more studies examining the relationship between cognitive
functions and swallowing function, and new approaches in rehabilitation of swallowing
disorders in line with these studies.
The purpose of this study was to conduct a meta-analysis of the effects of chewing gum on selective attention. A meta-analysis was conducted for each task (Flanker task, Stroop task, and Simon task) to evaluate selective attention, and the differences in the effects of chewing gum depending on the task format were also examined. The results confirmed a significant weak mean effect size for the fixed effect models in the analysis for the entire paper. However, because of significant heterogeneity across studies, we focused on the differences in task format and conducted a meta-analysis for each task assessing selective attention function. The results showed that there were no significant mean effect sizes in the fixed and random effect models for the Flanker and Stroop tasks. Meanwhile, significant mean effect sizes were found in the Simon task for both of the models. In conclusion, we can say that chewing gum has an effect of reducing the compatibility effect in the late phase of selective attention, especially when involving response selection.
This chapter delves into the crucial stomatognathic function of deglutition. By employing electromyography and mandibular scanning techniques, we can effectively identify various tongue dysfunctions that are of particular interest in the field of orthodontics. The author puts forth a hypothesis on primary and secondary tongue thrust, shedding light on this important aspect of the subject. It is imperative to note that an ideal dental occlusion cannot be achieved without an optimal swallow pattern. As such, identifying the correlation between tongue function and malocclusion is a crucial step in the diagnosis of neuromuscular orthodontic conditions. By exploring this link, we can gain a deeper understanding of the underlying factors contributing to the development of malocclusion and develop more effective treatment strategies. Continued exploration and investigation into the subject of deglutition and its relationship with orthodontic conditions is essential for advancing the field and improving patient outcomes.
Untreated early childhood caries (ECC) is a global public health concern. In the short term, untreated ECC can lead to pain, infection, and disrupted sleep, among other issues. In the long term, it is associated with poor oral health in later life, increased risk of caries in permanent teeth, and adverse effects on physical and psychological development. There may be a link between untreated ECC and adverse cognitive and neurodevelopmental outcomes in young children, although the exact pathways are not fully understood. One possible pathway is through the relationship between mastication and brain stimulation. Impaired masticatory function due to ECC can affect the hippocampus, a key region responsible for memory and learning. Furthermore, untreated ECC can cause chronic inflammation, leading to the release of pro-inflammatory cytokines that may damage the brain. Sleep disturbances resulting from ECC-related pain and discomfort can also impact brain development and cognitive functioning. Additionally, frequent use of antibiotics and analgesics to address ECC-related infections can disrupt the gut microbiome, potentially affecting the brain through the gut–brain axis. Untreated ECC can cause nutritional deficiencies and elevated nutritional risk, and can further hinder brain development. Addressing ECC comprehensively with early childhood health initiatives can help mitigate potential long-term consequences and promote optimal brain development in young children.
The current study aimed to add to this of knowledge by examining the effect of chewing gum on smoking withdrawal severity over a long period, as well as identifying the specific characteristics of chewing gum that may be responsible for the reported reductions in withdrawal. Chewing, flavour, and the combination of the two were all investigated separately. The study is based on quantitative research. The data has been classified on basis of smoker and non-smoker. Participants reported a significant difference in withdrawal severity across conditions using repeated measures Chi square, F(3, 69)=2.89, p.05. The flavoured gum condition had considerably lower withdrawal scores than the flavourless gum base and no product control conditions, according to follow-up analyses. These data suggest that chewing gum is effective in reducing the severity of nicotine withdrawal symptoms over a 24-hour period of nicotine abstinence, and that the impact is due to a combination of flavour and chewing. These findings, together with findings from previous laboratory studies, show that chewing gum could be a useful coping mechanism for those who are trying to quit smoking.
A very extensive literature review presents the possibilities and needs of using, in endodontics, the alloys commonly known as nitinol. Nitinol, as the most modern group of engineering materials used to develop root canals, is equilibrium nickel and titanium alloys in terms of the elements’ atomic concentration, or very similar. The main audience of this paper is engineers, tool designers and manufacturers, PhD students, and students of materials and manufacturing engineering but this article can also certainly be used by dentists. The paper aims to present a full material science characterization of the structure and properties of nitinol alloys and to discuss all structural phenomena that determine the performance properties of these alloys, including those applied to manufacture the endodontic tools. The paper presents the selection of these alloys’ chemical composition and processing conditions and their importance in the endodontic treatment of teeth. The results of laboratory studies on the analysis of changes during the sterilization of endodontic instruments made of nitinol alloys are also included. The summary of all the literature analyses is an SWOT analysis of strengths, weaknesses, opportunities, and threats, and is a forecast of the development strategy of this material in a specific application such as endodontics.
The paper is an extensive monographic review of the literature, and also uses the results of the authors’ own experimental research illustrating the noticed developmental tendencies of the filling material based on gutta-percha. The whole body of literature proves the correctness of the research thesis that this material is the best currently that can be used in endodontics. Caries is one of the most common global infectious diseases. Since the dawn of humankind, the consequence of the disease has been the loss of dentition over time through dental extractions. Both tooth caries and tooth loss cause numerous complications and systemic diseases, which have a serious impact on insurance systems and on the well-being, quality, and length of human life. Endodontic treatment, which has been developing since 1836, is an alternative to tooth extraction. Based on an extensive literature review, the methodology of qualifying patients for endodontic treatment was analyzed. The importance of selecting filling material and techniques for the development and obturation of the root canal during endodontic treatment was described. Particular attention was paid to the materials science aspects and the sequence of phase transformations and precipitation processes, as well as the need to ensure the stoichiometric chemical composition of Ni–Ti alloys, and the vacuum metallurgical processes and material processing technologies for the effects of shape memory and superelasticity, which determine the suitability of tools made of this alloy for endodontic purposes. The phenomena accompanying the sterilization of such tools, limiting the relatively small number of times of their use, play an important role. The methods of root canal preparation and obturation methods through cold side condensation and thermoplastic methods, including the most modern of them, the thermo-hydraulic condensation (THC) technique, were analyzed. An important element of the research hypothesis was to prove the assumption that to optimize the technology of development and obturation of root canals, tests of filling effectiveness are identified by the density and size of the gaps between the root canal wall, and the filling methods used and devices appropriate for material research, using mainly microscopy such as light stereoscopic (LSM) and scanning electron (SEM). The most beneficial preparations were obtained by making a longitudinal breakthrough of 48 natural human teeth, extracted for medical reasons, different from caries, with compliance with all ethical principles in this field. The teeth were prepared using various methods and filled with multiple obturation techniques, using a virtual selection of experimental variants. The breakthroughs were made in liquid nitrogen after a one-sided incision with a narrow gap created by a diamond disc using a materialographic cutter. The best effectiveness of the root canal filling was ensured by the technology of preparing the root canals with K3 rotary nitinol tools and filling the teeth with the THC thermoplastic method using the System B and Obtura III devices with studs and pellets of filling material based on gutta-percha after covering the root canal walls with a thin layer of AH Plus sealant. In this way, the research thesis was confirmed.
BACKGROUND: The establishment of appropriate vertical dimension of occlusion (VDO) is paramount for successful and functioning complete dentures (CDs). AIM: The aim of this study was to assess the effect of alteration of VDO on the brain activity in CD wearers. MATERIALS AND METHODS: Ten completely edentulous patients participated in this study. Each patient received three sets of CDs: one control set and two duplicates’ CDs. The control CDs was designed with appropriate VDO (control - VDO), while the duplicate CDs were designated as followed: one with VDO lowered by –3 mm (low - VDO) the other one VDO was increased by +5 mm (high - VDO). The effect of alteration of VDO on brain activity was assessed by measuring alpha waves changes using electroencephalogram (EEG) before and after chewing gum. Statistical analysis was carried out using one-way ANOVA and dependent t-test. The significance level was set at p < 0.05. RESULTS: There was a significant increase in the alpha waves mean values after chewing (p < 0.05) gum compared to before except for low - VDO CDs (p > 0.05). The control-VDO revealed a statistically significant higher mean values compared to the duplicate dentures. CDs with high - VDO showed higher mean value than low - VDO dentures, however, it was statistically insignificant (p > 0.05). CONCLUSION: Appropriate determination of VDO is not only important for the success of CDs but also for the functional augmentation of brain activity.
Mesencephalic trigeminal nucleus (MTN) neurons innervate the stretch receptors of the jaw elevator muscles and periodontal ligament mechanoreceptors, Bruxism activates the MTN. We analyzed how MTN cells are structured, their anatomy and physiology, and the effects of their activation.
To induce and maintain sleep, gamma-aminobutyric acid (GABA), an inhibitor neurotransmitter, is released from the ventro-lateral preoptic area of the hypothalamus and acts on the ascending reticular activating system (ARAS) nuclei. The GABA neurotrasmitter induces the entry of chlorine into cells, hyperpolarizing and inhibiting these. MTN cells, on the contrary, are depolarized by GABA, as their receptors are activated upon GABA binding. They “let out” chlorine and activate ARAS cells. MTN cells release glutamate, an excitatory neurotransmitter onto their target cells, in this case onto ARAS cells. During wakefulness, ARAS activation causes cerebral cortex activation; instead, during sleep (sleep bruxism), ARAS activation avoids an excessive reduction in ARAS neurotransmitters, including noradrenaline, dopamine, serotonin, acetylcholine and glutamate. These neurotransmitters, in addition to activating the cerebral cortex, modulate vital functions such as cardiac and respiratory functions. Polysomnography shows that sleep bruxism is always accompanied by cardiac and respiratory activation and, most importantly, by brain function activation. Bruxism is not a parafunction, and it functions to activate ARAS nuclei.
Background:
Mastication improves cognitive function by activating cerebral cortical activity, and it is important to demonstrate the cognitive effects of masticatory training using a variety of different interventions.
Objective:
This study aimed to evaluate the effects of masticatory exercise on cognitive function in healthy older adults living in the community.
Methods:
For six weeks, twelve participants performed a masticatory exercise using a NOSICK exerciser device, and thirteen subjects performed daily life without masticatory exercises. Trail Making Test, Digit Span Test, and Stroop test were used to measure the cognitive function.
Results:
The participants in the experimental group showed significant improvements in TMT-A/B (p= 0.001 and 0.004), DST-forward (p= 0.001), and ST-word (p= 0.001). The effect sizes after the intervention were calculated as (1.2 and 0.8) for TMT-A/B, (0.8 and 0.2) for Digit Span Test forward/backward, and (0.6 and 0.2) for Stroop test color/word.
Conclusions:
We suggest that the masticatory exercises improve cognitive function in healthy older adults. Therefore, masticatory exercises can be used as a therapeutic exercise during cognitive rehabilitation.
Trigeminal input exerts acute and chronic effects on the brain, modulating cognitive functions. Here, new data from humans and animals suggest that these effects are caused by trigeminal influences on the Locus Coeruleus (LC). In humans subjects clenching with masseter asymmetric activity, occlusal correction improved cognition, alongside with reductions in pupil size and anisocoria, proxies of LC activity and asymmetry, respectively. Notably, reductions in pupil size at rest on the hypertonic side predicted cognitive improvements. In adult rats, a distal unilateral section of the trigeminal mandibular branch reduced, on the contralateral side, the expression of c-Fos (brainstem) and BDNF (brainstem, hippocampus, frontal cortex). This counterintuitive finding can be explained by the following model: teeth contact perception loss on the lesioned side results in an increased occlusal effort, which enhances afferent inputs from muscle spindles and posterior periodontal receptors, spared by the distal lesion. Such effort leads to a reduced engagement of the intact side, with a corresponding reduction in the afferent inputs to the LC and in c-Fos and BDNF gene expression. In conclusion, acute effects of malocclusion on performance seem mediated by the LC, which could also contribute to the chronic trophic dysfunction induced by loss of trigeminal input.
Objective: Malocclusion has been reported to affect the daily lives of schoolchildren adversely, but little is known regarding the association between malocclusion and academic performance. We aimed to investigate the association between malocclusion and academic performance among adolescents in Mongolia.
Methods: We conducted a cross-sectional study of 767 students aged 7–16 years from two public schools in Ulaanbaatar, Mongolia. Three orthodontists evaluated the need for malocclusion treatment in the participants and determined the type of malocclusion using the Index of Orthodontic Treatment Need and dental casts. The academic scores of study participants in 20 subjects were provided by their schools. Z-scores within subjects were calculated and aggregated into both overall and in six groups of subject categories comprised of mathematics, science, social science, language, arts, and physical education. A multiple linear regression analysis was performed to determine the association between malocclusion, malocclusion type, and academic score adjusted for gender, age, school, and family income.
Results: Of the 767 students, 32.6% had malocclusion, and dental crowding was the most prevalent type (162 cases, 21.1%). Malocclusion was not significantly associated with the z-score of overall academic score [coefficient: 0.04, 95% confidence interval (CI): −0.11 to 0.19]; however, dental crowding was significantly associated with the overall academic score (coefficient: −0.19, 95% CI: −0.35 to −0.03), after adjusting for covariates. Other types of malocclusion were not associated with academic scores. Among the six subject categories, arts (coefficient: −0.20, 95% CI: −0.36 to −0.04) and physical education (coefficient: −0.24, 95% CI: −0.42 to −0.07) were significantly associated with dental crowding.
Conclusions: Schoolchildren in Mongolia with dental crowding may be prone to poor academic performance, particularly in arts and physical education classes. Further randomized controlled trials are needed to determine whether the treatment of crowding boosts academic performance.
This paper concerns the assessment of the current state of dentistry in the world and the prospects of its sustainable development. A traditional Chinese censer was adopted as the pattern, with a strong and stable support on three legs. The dominant diseases of the oral cavity are caries and periodontal diseases, with the inevitable consequence of toothlessness. From the caries 3.5–5 billion people suffer. Moreover, each of these diseases has a wide influence on the development of systemic complications. The territorial range of these diseases and their significant differentiation in severity in different countries and their impact on disability-adjusted life years index are presented (DALY). Edentulousness has a significant impact on the oral health-related quality of life (OHRQoL). The etiology of these diseases is presented, as well as the preventive and therapeutic strategies undertaken as a result of modifying the Deming circle through the fives’ rules idea. The state of development of Dentistry 4.0 is an element of the current stage of the industrial revolution Industry 4.0 and the great achievements of modern dental engineering. Dental treatment examples from the authors’ own clinical practice are given. The systemic safety of a huge number of dentists in the world is discussed, in place of the passive strategy of using more and more advanced personal protective equipment (PPE), introducing our own strategy for the active prevention of the spread of pathogenic microorganisms, including SARS-CoV-2. The ethical aspects of dentists’ activity towards their own patients and the ethical obligations of the dentist community towards society are discussed in detail. This paper is a polemic arguing against the view presented by a group of eminent specialists in the middle of last year in The Lancet. It is impossible to disagree with these views when it comes to waiting for egalitarianism in dental care, increasing the scope of prevention and eliminating discrimination in this area on the basis of scarcity and poverty. The views on the discrimination of dentistry in relation to other branches of medicine are far more debatable. Therefore, relevant world statistics for other branches of medicine are presented. The authors of this paper do not agree with the thesis that interventional dental treatment can be replaced with properly implemented prophylaxis. The final remarks, therefore, present a discussion of the prospects for the development of dentistry based on three pillars, analogous to the traditional Chinese censer obtaining a stable balance thanks to its three legs. The Dentistry Sustainable Development (DSD) > 2020 model, consisting of Global Dental Prevention (GDP), Advanced Interventionist Dentistry 4.0 (AID 4.0), and Dentistry Safety System (DSS), is presented.
Chewing gum has been shown to reliably increase subjective alertness whereas the effects on attention are more variable. It has been suggested that chewing gum only enhances attention when the person has been performing a task for some time.
The current research aimed to investigate if time-on-task trends enhancing effects of chewing gum could be observed in alertness and attention during and following chewing.
Study 1 used tests of reported mood, including reported mood, and tests of attention (categoric search, focussed attention, simple reaction time, and vigilance). These tasks were performed shortly after the start of chewing. Study 2 examined effects of previous and current chewing on reported alertness and the attention tests.
Study 1 showed that chewing gum increased reported alertness and hedonic tone and improved performance on the categoric search task. Chewing gum maintained reported alertness across sessions in study 2. In the first experimental session of study 2 gum improved categoric search performance, and during the second session gum broadened focus of attention and quickened vigilance reaction time. This effect on vigilance reaction time was moderated by time-on-task, with an initial negative effect being replaced by a positive effect.
The results confirm the robust effect of chewing gum on reported alertness and show that changes in the effects of chewing gum on attention require further investigation. Future research may also determine underlying mechanisms for an alerting effect.
The current series of experiments investigated the effects of the timing of gum chewing on cognitive function, by administering a battery of cognitive tasks to participants who chewed gum either prior to or throughout testing, and comparing their performance to that of controls who did not chew gum. Chewing gum was associated with performance advantages on multiple measures when gum was chewed for 5 min before, but not during, cognitive testing. The benefits, however, persisted only for the first 15-20 min of the testing session, and did not extend to all cognitive domains. To explain this pattern of results, it is proposed that the time-limited nature of performance benefits can be attributed to mastication-induced arousal. Furthermore, the lack of improvement in cognitive function when gum is chewed throughout testing may be because of interference effects due to a sharing of resources by cognitive and masticatory processes. This dual-process mechanism is not only consistent with the outcome of present experiments but can potentially account for a wide range of findings reported in the literature.
Recent research suggests that chewing gum may improve aspects of cognitive function and mood. There is also evidence suggesting that chewing gum reduces stress. It is important, therefore, to examine these two areas and to determine whether contextual factors (chewing habit, type of gum, and personality) modify such effects.
The aims of the present study were: (i) to determine whether chewing gum improved mood and mental performance; (ii) to determine whether chewing gum had benefits in stressed individuals; and (iii) to determine whether chewing habit, type of gum and level of anxiety modified the effects of gum.
A cross-over study involving 133 volunteers was carried out. Each volunteer carried out a test session when they were chewing gum and without gum, with order of gum conditions counterbalanced across subjects. Baseline sessions were conducted prior to each test session. Approximately half of the volunteers were tested in 75 dBA noise (the stress condition) and the rest in quiet. Volunteers were stratified on chewing habit and anxiety level. Approximately, half of the volunteers were given mint gum and half fruit gum. The volunteers rated their mood at the start and end of each session and had their heart rate monitored over the session. Saliva samples were taken to allow cortisol levels (good indicator of alertness and stress) to be assayed. During the session, volunteers carried out tasks measuring a range of cognitive functions (aspects of memory, selective and sustained attention, psychomotor speed and accuracy).
Chewing gum was associated with greater alertness and a more positive mood. Reaction times were quicker in the gum condition, and this effect became bigger as the task became more difficult. Chewing gum also improved selective and sustained attention. Heart rate and cortisol levels were higher when chewing which confirms the alerting effect of chewing gum.
Overall, the results suggest that chewing gum produces a number of benefits that are generally observed and not context-dependent. In contrast to some previous research, chewing gum failed to improve memory. Further research is now required to increase our knowledge of the behavioral effects of chewing gum and to identify the underlying mechanisms.
Recent research suggests that chewing gum may increase alertness and lead to changes in cognitive performance. The present study examined effects of chewing gum on these functions within the context of a single study.
This study had four main aims. The first was to examine whether chewing gum improved learning and memory of information in a story. The second aim was to determine whether chewing gum improved test performance on a validated intellectual task (the Alice Heim task). A third aim was to determine whether chewing gum improved performance on short memory tasks (immediate and delayed recall of a list of words, delayed recognition memory, retrieval from semantic memory, and a working memory task). The final aim was to determine whether chewing gum improved mood (alertness, calm and hedonic tone).
A cross-over design was used with gum and no-gum sessions being on consecutive weeks. In each week, volunteers attended for two sessions, two days apart. The first session assessed mood, immediate recall of information from a story and performance on short memory tasks. The second session assessed mood, delayed recall of information from a story and performance of an intelligence test (the Alice Heim test).
There were no significant effects of chewing gum on any aspect of recall of the story. Chewing gum improved the accuracy of performing the Alice Heim test which confirms the benefits of gum on test performance seen in an earlier study. Chewing gum had no significant effect on the short memory tasks. Chewing gum increased alertness at the end of the test session in both parts of the study. This effect was in the region of a 10% increase and was highly significant (P < 0.001).
The results of this study showed that chewing gum increases alertness. In contrast, no significant effects of chewing gum were observed in the memory tasks. Intellectual performance was improved in the gum condition. Overall, the results suggest further research on the alerting effects of chewing gum and possible improved test performance in these situations.
Recent research has shown that even small doses (<40mg) of caffeine can improve alertness and increase performance efficiency on attention tasks. Previous studies have given the caffeine in a variety of beverages or in capsules and it was of interest to see whether similar effects could be observed when the caffeine was given in gum. In addition, chewing gum has been shown to have behavioural effects and the present study extended our knowledge of this topic.
To compare the effects of caffeinated gum (40 mg), placebo gum and no gum conditions on mood and attention.
A double blind placebo controlled study was conducted with volunteers being randomly assigned to one of the three conditions. Baseline measures of mood and attention were taken prior to chewing and a test session was then conducted. One hundred and eighteen young adults participated in the study.
Caffeinated gum was associated with a more positive mood and better performance on tasks requiring sustained attention. The caffeine improved the speed of encoding of new information which is consistent with previous findings. Chewing placebo gum was also found to be associated with more positive mood, both shortly after chewing and at the end of the study.
The implications of the present study are that chewing caffeinated gum has been shown to improve performance efficiency and mood by its alerting and energising effects. The profile of caffeine effects is what one would predict from the existing caffeine literature and such effects may be extremely beneficial in real-life situations. Prior chewing of placebo gum was associated with a more positive mood and this also confirms previous findings.
: The concept of attention as central to human performance extends back to the start of experimental psychology, yet even a few years ago, it would not have been possible to outline in even a preliminary form a functional anatomy of the human attentional system. New developments in neuroscience have opened the study of higher cognition to physiological analysis, and have revealed a system of anatomical areas that appear to be basic to the selection of information for focal (conscious) processing. The importance of attention is its unique role in connecting the mental level of description of processes used in cognitive science with the anatomical level common in neuroscience. Sperry describes the central role that mental concepts play in understanding brain function. As is the case for sensory and motor systems of the brain, our knowledge of the anatomy of attention is incomplete. Nevertheless, we can now begin to identify some principles of organization that allow attention to function as a unified system for the control of mental processing. Although many of our points are still speculative and controversial, we believe they constitute a basis for more detailed studies of attention from a cognitive-neuroscience viewpoint. Perhaps even more important for furthering future studies, multiple methods of mental chronometry, brain lesions, electrophysiology, and several types of neuro-imaging have converged on common findings.
The interaction between mastication and cerebral blood flow was studied in 12 healthy volunteers (five males and seven females) aged 18-40 years. Positron-emission tomography (PET) autoradiography was carried out after bolus injection of 1.5 GBq H₂¹⁵O (¹⁵O-labelled water) with a half life of 2 min. The PET images were superimposed on magnetic resonance images of each participant. The regional cerebral blood flow images were normalized by the global cerebral blood flow value, and subtraction images (those during gum-chewing minus those during resting) were created and recut at the magnetic resonance image slice positions. Gum specially designed for chewing training was used. Mastication increased regional cerebral blood flow in the primary sensorimotor areas by 25-28%, in the supplementary motor areas and insulae by 9-17%, and in the cerebellum and striatum by 8-11%. These increases demonstrate that chewing activates widespread regions of the brain.
Theories of motor control postulate that the brain uses internal models of the body to control movements accurately. Internal models are neural representations of how, for instance, the arm would respond to a neural command, given its current position and velocity. Previous studies have shown that the cerebellar cortex can acquire internal models through motor learning. Because the human cerebellum is involved in higher cognitive function as well as in motor control, we propose a coherent computational theory in which the phylogenetically newer part of the cerebellum similarly acquires internal models of objects in the external world. While human subjects learned to use a new tool (a computer mouse with a novel rotational transformation), cerebellar activity was measured by functional magnetic resonance imaging. As predicted by our theory, two types of activity were observed. One was spread over wide areas of the cerebellum and was precisely proportional to the error signal that guides the acquisition of internal models during learning. The other was confined to the area near the posterior superior fissure and remained even after learning, when the error levels had been equalized, thus probably reflecting an acquired internal model of the new tool.
It is suggested that mastication stimulates the brain and accelerates its energy-consuming metabolism. This study was designed to determine its effects on regional cerebral blood flow (rCBF) using xenon-enhanced computed tomography (Xe-CT). Seven male volunteers, aged 24-57 years, inhaled 30% xenon in a 4 minutes wash-in and 4 minutes wash-out protocol. CT was scanned every 54.5 seconds. The subjects were instructed to chew a gum continuously at a rate of 1 bite per second except at the time of CT scanning (5.5 seconds). A second CBF was done 20 minutes later. Subtraction (mastication-baseline) maps were created. CT images were taken at three levels so as to include the cortex, basal ganglia, limbic system, brainstem and cerebellum. The results demonstrated a significant rCBF increase in the fronto-temporal cortex, caudate nucleus, thalamus and minor increase in the rolandic areas, insula, cingulate and cerebellum. Further studies are needed to validate the clinical significance of these findings.
People adapt with remarkable flexibility to reversal of the visual field caused by prism spectacles. With sufficient time, this adaptation restores visually guided behaviour and perceptual harmony between the visible and tactile worlds. Although it has been suggested that seeing one's own body is crucial for adaptation, the underlying mechanisms are unclear. Here we show that a new representation of visuomotor mapping with respect to the hands emerges in a month during adaptation to reversed vision. The subjects become bi-perceptual, or able to use both new and old representations. In a visual task designed to assess the new hand representation, subjects identified visually presented hands as left or right by matching the picture to the representation of their own hands. Functional magnetic resonance imaging showed brain activity in the left posterior frontal cortex (Broca's area) that was unique to the new hand representations of both hands, together with activation in the intraparietal sulcus and prefrontal cortex. The emergence of the new hand representation coincided with the adaptation of perceived location of visible objects in space. These results suggest that the hand representation operates as a visuomotor transformation device that provides an arm-centred frame of reference for space perception.
In recent years, three attentional networks have been defined in anatomical and functional terms. These functions involve alerting, orienting, and executive attention. Reaction time measures can be used to quantify the processing efficiency within each of these three networks. The Attention Network Test (ANT) is designed to evaluate alerting, orienting, and executive attention within a single 30-min testing session that can be easily performed by children, patients, and monkeys. A study with 40 normal adult subjects indicates that the ANT produces reliable single subject estimates of alerting, orienting, and executive function, and further suggests that the efficiencies of these three networks are uncorrelated. There are, however, some interactions in which alerting and orienting can modulate the degree of interference from flankers. This procedure may prove to be convenient and useful in evaluating attentional abnormalities associated with cases of brain injury, stroke, schizophrenia, and attention-deficit disorder. The ANT may also serve as an activation task for neuroimaging studies and as a phenotype for the study of the influence of genes on attentional networks.
Inferring resting-state connectivity patterns from functional magnetic resonance imaging (fMRI) data is a challenging task for any analytical technique. In this paper, we review a probabilistic independent component analysis (PICA) approach, optimized for the analysis of fMRI data, and discuss the role which this exploratory technique can take in scientific investigations into the structure of these effects. We apply PICA to fMRI data acquired at rest, in order to characterize the spatio-temporal structure of such data, and demonstrate that this is an effective and robust tool for the identification of low-frequency resting-state patterns from data acquired at various different spatial and temporal resolutions. We show that these networks exhibit high spatial consistency across subjects and closely resemble discrete cortical functional networks such as visual cortical areas or sensory-motor cortex.
Before considering a given fMRI paradigm as a valid clinical tool, one should first assess the reliability of functional responses across subjects by establishing a normative database and defining a reference activation map that identifies major brain regions involved in the task at hand. However, the definition of such a reference map can be hindered by inter-individual functional variability. In this study, we analysed functional data obtained from 50 healthy subjects during a semantic language task to assess the influence of the number of subjects on the reference map and to characterise inter-individual functional variability. We first compared different group analysis approaches and showed that the extent of the activated network depends not only on the choice of the analysis approach but also on the statistical threshold used and the number of subjects included. This analysis suggested that, while the RFX analysis is suitable to detect confidently true positive activations, the other group approaches are useful for exploratory investigations in small samples. The application of quantitative measures at the voxel and regional levels suggested that while approximately 15-20 subjects were sufficient to reveal reliable and robust left hemisphere activations, >30 subjects were necessary for revealing more variable and weak right hemisphere ones. Finally, to visualise inter-individual variability, we combined two similarity indices that assess the percentages of true positive and false negative voxels in individual activation patterns relative to the group map. We suggest that these measures can be used for the estimation of the degree of 'normality' of functional responses in brain-damaged patients, where this question is often raised, and recommend the use of different quantifications to appreciate accurately the inter-individual functional variability that can be incorporated in group maps.
Anterior cingulate cortex (ACC) is a part of the brain's limbic system. Classically, this region has been related to affect, on the basis of lesion studies in humans and in animals. In the late 1980s, neuroimaging research indicated that ACC was active in many studies of cognition. The findings from EEG studies of a focal area of negativity in scalp electrodes following an error response led to the idea that ACC might be the brain's error detection and correction device. In this article, these various findings are reviewed in relation to the idea that ACC is a part of a circuit involved in a form of attention that serves to regulate both cognitive and emotional processing. Neuroimaging studies showing that separate areas of ACC are involved in cognition and emotion are discussed and related to results showing that the error negativity is influenced by affect and motivation. In addition, the development of the emotional and cognitive roles of ACC are discussed, and how the success of this regulation in controlling responses might be correlated with cingulate size. Finally, some theories are considered about how the different subdivisions of ACC might interact with other cortical structures as a part of the circuits involved in the regulation of mental and emotional activity.
Finding a non-pharmacological adjunct to enhance cognitive processing in humans would be beneficial to numerous individuals. Past research has consistently noted a significant interplay between odors and human behavior; for example, the administration of particular odorants enhances athletic performance, mood, and sleep quality. In addition, odorants have a differential effect on human behavior, dependent upon route of administration (retronasal vs. orthonasal). The following study examined the differential effects of odorants on cognition based upon route of administration. During Phase 1, 31 participants completed cognitive tasks on a computer-based program (Impact©) under five "chewing gum" conditions (no gum, flavorless gum, peppermint gum, cinnamon gum, and cherry gum). During Phase II, 39 participants completed the cognitive tasks under four odorant conditions (no odor, peppermint odor, jasmine odor, and cinnamon odor). Results revealed a task-dependent relationship between odors and the enhancement of cognitive processing. Specifically, cinnamon, administered retronasally and orthonasally, improved participants' scores on tasks related to attentional processes, virtual recognition memory, working memory, and visual-motor response speed. Implications are discussed in relation to providing a non-pharmacological adjunct to enhance cognition in the elderly, individuals with test-anxiety, and those with symptoms of dementia.
This study tests the hypothesis that chewing gum leads to cognitive benefits through improved delivery of glucose to the brain, by comparing the cognitive performance effects of gum and glucose administered separately and together. Participants completed a battery of cognitive tests in a fully related 2×2 design, where one factor was Chewing Gum (gum vs. mint sweet) and the other factor was Glucose Co-administration (consuming a 25 g glucose drink vs. consuming water). For four tests [Auditory Verbal Learning Task (AVLT) Recall, Digit Span, Spatial Span and Grammatical Transformation), beneficial effects of chewing and glucose were found, supporting the study hypothesis. However, on AVLT Delayed Recall, enhancement due to chewing gum was not paralleled by glucose enhancement, suggesting an alternative mechanism. The glucose delivery model is supported with respect to the cognitive domains: working memory, immediate episodic long-term memory and language-based attention and processing speed. However, some other mechanism is more likely to underlie the facilitatory effect of chewing gum on delayed episodic long-term memory.
Two experiments independently investigated the basis of the chewing-gum induced context-dependent memory effect (Baker, Bezance, Zellaby, & Aggleton, 2004). At learning and/or recall participants either chewed flavourless gum (Experiment 1) or received mint-flavoured strips (Experiment 2). No context dependent memory effect was found with either flavourless gum or mint-flavoured strips, indicating that independently the contexts were insufficiently salient to induce the effect. This is found despite participants’ subjective ratings indicating a perceived change in internal state following administration of flavourless gum and mint-flavoured strips. Additionally, some preliminary evidence for a non-additive facilitative effect on memory of receiving gum or flavour at either learning and/or recall is reported. The findings raise further concerns regarding the robustness of the previously context-dependent memory effect with chewing gum.
Baker, J. B., Bezance, E., Zellaby, & Aggleton, J. P. (2004). Chewing gum can produce context-dependent effects upon memory. Appetite, 43, 207–210.
Statistical parametric maps are spatially extended statistical processes that are used to test hypotheses about regionally specific effects in neuroimaging data. The most established sorts of statistical parametric maps (e.g., Friston et al. [1991]: J Cereb Blood Flow Metab 11:690–699; Worsley et al. [1992]: J Cereb Blood Flow Metab 12:900–918) are based on linear models, for example ANCOVA, correlation coefficients and t tests. In the sense that these examples are all special cases of the general linear model it should be possible to implement them (and many others) within a unified framework. We present here a general approach that accomodates most forms of experimental layout and ensuing analysis (designed experiments with fixed effects for factors, covariates and interaction of factors). This approach brings together two well established bodies of theory (the general linear model and the theory of Gaussian fields) to provide a complete and simple framework for the analysis of imaging data.
The importance of this framework is twofold: (i) Conceptual and mathematical simplicity, in that the same small number of operational equations is used irrespective of the complexity of the experiment or nature of the statistical model and (ii) the generality of the framework provides for great latitude in experimental design and analysis.
Recent research examined the effects of chewing gum on attention and reported a significant interaction of gum chewing with time. Using a crossover within-subject design, the present study examined the effect of gum chewing on sustained attention in healthy adults over a period of 30 min. The results revealed a significant main effect of time and a significant interaction between gum chewing and time. The findings suggest that gum chewing differentially affects attention performance. While gum chewing has detrimental effects on sustained attention in earlier stages of the task, beneficial effects on sustained attention were observed at later stages.
Impairments of attention are cardinal features of attention deficit hyperactivity disorder (ADHD) and can seriously affect the daily life of children with ADHD. Despite effective treatment strategies, there is a need of further treatment options that can be added to available and well established treatments. Further treatment options are needed since available treatments are often time consuming, expensive and limited regarding their external validity. Recent research demonstrated that gum chewing has beneficial effects on cognition including certain aspects of attention. Therefore, gum chewing may benefit children with ADHD in situations requiring particular cognitive efforts. In a crossover study, attentional functioning of 32 children with ADHD and 32 children without the condition was examined. All participants were assessed with chewing gum and without chewing gum. A computerized test was used for the assessment of vigilance and sustained attention. The findings of the present study suggest that gum chewing during task execution has detrimental effects on vigilance of both healthy children and children with ADHD. Sustained attention was not affected by gum chewing. Chewing gum, therefore, appears not to improve attentional performance in children with ADHD.
Control of attention is a key mechanism underlying behavior regulation. In this study we detail the aspects of attention that covary with the chronic use of cannabis throughout adolescence. We compared performance and brain activation differences in tasks involving attention between young adults with a history of chronic cannabis use during adolescence and matched non-user control subjects. Two tasks were used to activate attention networks: the Attention Network Task (ANT) and the use generation task. In the ANT, chronic users (N=14) differed from controls (N=14) in showing poorer performance (longer reaction time and more errors) on tasks requiring processing of incongruent stimuli reflecting the executive attention network, but not in networks related to alerting or orienting components of attention. Functional MRI of brain activity showed stronger activation within the right prefrontal cortex in chronic users compared to the control group specifically on ANT trials requiring executive attention. The use generation task also revealed significantly stronger activation of the same right prefrontal area in users compared to controls. These results suggest that chronic cannabis users have less efficient executive attention in conflict resolution tasks, demanding more activation in the right prefrontal areas to resolve conflict.
Efficient attention is pivotal for cognitive functioning, and individual differences in attentional functions are likely related to variations in structural properties of the brain. Attention is supported by separate processes, and models of the relationship between attention and brain structure must take this into account. The Attention Network Test (ANT) yields behavioral measures of 3 independent attentional components: executive control (EC), alerting, and orienting. EC relates to resolving cognitive interference, alerting refers to continuous maintenance of a vigilant state, and orienting to selection of and orienting toward sensory information. Evidence from functional neuroimaging studies suggests that the ANT components recruit different cortical networks. However, the structural correlates are not established. Therefore, ANT scores were correlated with cortical thickness across the brain surface in 268 healthy adults spanning 20-84 years of age. Specific correlations were found between cortical thickness and EC and alerting in regions implicated by functional neuroimaging and lesion studies, including anterior cingulate, lateral prefrontal, and right inferior frontal gyri for EC and parietal areas for alerting. The brain-behavior correlations were relatively stable across adulthood, indicating that factors influencing cortical maturation rather than aging-related atrophy specifically were instrumental in shaping the structural foundation for visuospatial attention in adults.
The effect of chewing gum on performance was examined. Four Grade 3 (8- to 9-year-olds) classes in a German primary school participated; 2 class-es chewed gum during a 16-min. concentration test. Chewing gum had a significant and positive effect on concentration performance.
Using functional magnetic resonance imaging (fMRI) in eight healthy human subjects, the present study measured blood oxygenation level-dependent (BOLD) signals during clenching in a malocclusion model, using a custom-made splint that forced the mandible to a retrusive position and a splint of no modification for control, and compared the results to the BOLD signals during the corresponding resting conditions. An individual visual analog scale (VAS) score was also examined during clenching to evaluate the interactions between fMRI data and psychiatric changes. During both clenchings, activations in four brain regions (premotor cortex, prefrontal cortex, sensorimotor cortex, and insula) were seen. However, clenching in the malocclusion model, with psychological discomfort, increased additionally BOLD signals in the anterior cingulate cortex and the amygdala. Furthermore, there was a parallel relationship between BOLD signal intensities and VAS scores in these two regions. The findings may suggest the involvement of clenching with malocclusal conditions in the emotion and/or pain-related neural processing in the brain.
The purpose of the present study was to clarify the effect of mastication on cognitive processing using reaction time (RT) and event-related potentials (ERPs).
The two experiments consisted of two conditions, Mastication (chewing gum) and Control (relaxing without chewing gum) in Experiment 1, and Jaw Movement (opening and closing the jaw) and Finger Tapping (tapping the right index finger) in Experiment 2. The subjects performed four sessions of an auditory oddball paradigm. RT and ERPs were recorded in these four sessions, Pre (before chewing), and Post 1, Post 2 and Post 3 (after chewing).
In Mastication for RT and the peak latencies of P300 and N100, the values were significantly longer in Pre than in Post 2 or Post 3. By contrast, in Control, Jaw Movement, and Finger Tapping, they were almost identical among sessions or significantly shorter in Pre than in Post 2 or Post 3.
Mastication influences cognitive processing time as reflected by RT and the latency of ERP waveforms.
This is the first study investigating the effect of mastication on the central nervous system using event-related potentials.
In both diagnostic and research applications, the interpretation of MR images of the human brain is facilitated when different data sets can be compared by visual inspection of equivalent anatomical planes. Quantitative analysis with predefined atlas templates often requires the initial alignment of atlas and image planes. Unfortunately, the axial planes acquired during separate scanning sessions are often different in their relative position and orientation, and these slices are not coplanar with those in the atlas. We have developed a completely automatic method to register a given volumetric data set with Talairach stereotaxic coordinate system.
The registration method is based on multi-scale, three-dimensional (3D) cross-correlation with an average (n > 300) MR brain image volume aligned with the Talariach stereotaxic space. Once the data set is re-sampled by the transformation recovered by the algorithm, atlas slices can be directly superimposed on the corresponding slices of the re-sampled volume. the use of such a standardized space also allows the direct comparison, voxel to voxel, of two or more data sets brought into stereotaxic space.
With use of a two-tailed Student t test for paired samples, there was no significant difference in the transformation parameters recovered by the automatic algorithm when compared with two manual landmark-based methods (p > 0.1 for all parameters except y-scale, where p > 0.05). Using root-mean-square difference between normalized voxel intensities as an unbiased measure of registration, we show that when estimated and averaged over 60 volumetric MR images in standard space, this measure was 30% lower for the automatic technique than the manual method, indicating better registrations. Likewise, the automatic method showed a 57% reduction in standard deviation, implying a more stable technique. The algorithm is able to recover the transformation even when data are missing from the top or bottom of the volume.
We present a fully automatic registration method to map volumetric data into stereotaxic space that yields results comparable with those of manually based techniques. The method requires no manual identification of points or contours and therefore does not suffer the drawbacks involved in user intervention such as reproducibility and interobserver variability.
Anterior cingulate cortex (ACC) is a part of the brain's limbic system. Classically, this region has been related to affect, on the basis of lesion studies in humans and in animals. In the late 1980s, neuroimaging research indicated that ACC was active in many studies of cognition. The findings from EEG studies of a focal area of negativity in scalp electrodes following an error response led to the idea that ACC might be the brain's error detection and correction device. In this article, these various findings are reviewed in relation to the idea that ACC is a part of a circuit involved in a form of attention that serves to regulate both cognitive and emotional processing. Neuroimaging studies showing that separate areas of ACC are involved in cognition and emotion are discussed and related to results showing that the error negativity is influenced by affect and motivation. In addition, the development of the emotional and cognitive roles of ACC are discussed, and how the success of this regulation in controlling responses might be correlated with cingulate size. Finally, some theories are considered about how the different subdivisions of ACC might interact with other cortical structures as a part of the circuits involved in the regulation of mental and emotional activity.
Acoustic noise levels for fast MRI pulse sequences were surveyed on 14 systems with field strengths ranging from 0.2 T to 3 T. A microphone insensitive to the magnetic environment was placed close to the magnet isocenter and connected via an extension cable to a sound level meter outside the scan room. Measured noise levels varied from 82.5 +/- 0.1 dB(A) for a 0.23 T system to 118.4 +/- 1.3 dB(A) for a 3 T system. Further measurements on four of the closed-bore systems surveyed showed that: 1) pulse sequence parameters (particularly FOV and TR) were more influential in determining noise level than field strength, 2) the noise level was found to vary along the z-direction with a maximum near the bore entrance, and 3) in one of two systems tested there was a significant increase in noise with a volunteer present instead of a test object. The results underline the importance of hearing protection for patients and for staff spending extended periods in the scan room.
Mastication has been suggested to increase neuronal activities in various regions of the human brain. However, because of technical difficulties, the fine anatomical and physiological regions linked to mastication have not been fully elucidated. Using functional magnetic resonance imaging during cycles of rhythmic gum-chewing and no chewing, we therefore examined the interaction between chewing and brain regional activity in 17 subjects (aged 20-31 years). In all subjects, chewing resulted in a bilateral increase in blood oxygenation level-dependent (BOLD) signals in the sensorimotor cortex, supplementary motor area, insula, thalamus, and cerebellum. In addition, in the first three regions, chewing of moderately hard gum produced stronger BOLD signals than the chewing of hard gum. However, the signal was higher in the cerebellum and not significant in the thalamus, respectively. These results suggest that chewing causes regional increases in brain neuronal activities which are related to biting force.
Tasks involving conflict between stimulus dimensions have been shown to activate dorsal anterior cingulate and prefrontal areas. It has been proposed that the dorsal anterior cingulate is involved a domain general process of monitoring conflict, while prefrontal areas are involved in resolving conflict. We examine three tasks that all require people to respond based on one stimulus dimension while ignoring another conflicting dimension, but which vary in the source of conflict. One of the tasks uses language stimuli (Stroop effect) and two use nonlanguage spatial conflicts appropriate for children and nonhuman animals. In Experiment 1, 12 participants were studied with event-related functional magnetic resonance imaging (fMRI) while performing each of the three tasks. Reaction times for each of the three tasks were significantly longer in the incongruent condition compared with the congruent condition, demonstrating that each task elicits a conflict. By studying the same people in the same session, we test the hypothesis that conflict activates a similar brain network in the three tasks. Significant activations were found in the anterior cingulate and left prefrontal cortex for all three conflict tasks. Within these regions, the conflict component demonstrated evidence for significant common activation across the three tasks, although the peak activation point and spatial extent were not identical. Other areas demonstrated activation unique to each task. Experiments 2-4 provide behavioral evidence indicating considerable independence between conflict operations involved in the tasks. The behavioral and fMRI results taken together seem to argue against a single unified network for processing conflict, but instead support either distinct networks for each conflict task or a single network that monitors conflict with different sites used to resolve the conflict.
This study used functional magnetic resonance images (fMRI) to examine brain activity during clenching, gum chewing, and tapping tasks. It has been considered difficult to obtain sufficient fMRI data during jaw movement because the head motion associated with the jaw movements creates artifacts on the images. To avoid these artifacts, larger pixels were used, thus allowing some head motion of the subjects, and data from subjects where the heads were evaluated to have moved more than 0.5 mm were discarded. Further, all pixels obtained by fMRI were evaluated and pixels positively synchronized with the task, which were considered to show brain activity, were selected. Sufficient fMRI data was obtained from 30 experiments, 10 sets for each task. During the clenching and tapping tasks, the activated pixels were in the sensory, motor and pre-motor cortexes, and in the sensory and motor cortexes but not in the pre-motor cortex during the gum chewing task. There appears to be no significant differences between right- and left-hemispheres. It is conceivable that there are differences between voluntary jaw movements (clenching and tapping tasks) and mastication (gum chewing task) concerning the control of jaw movements.
Age-related changes in mastication-induced brain neuronal activity have been suggested. However, in humans, little is known about the anatomical regions involved. Using fMRI during cycles of rhythmic gum-chewing and no chewing, we have examined the effect of aging on brain regional activity during chewing in young adult (19-26 yrs), middle-aged (42-55 yrs), and aged (65-73 yrs) healthy humans. In all subjects, chewing resulted in a bilateral increase in the BOLD signals in the sensorimotor cortex, cerebellum, thalamus, supplementary motor area, and insula, and a unilateral increase in the right prefrontal area. In the first three regions, the signal increases were attenuated in an age-dependent manner, whereas, in the right prefrontal area, the converse was seen. The remaining two regions showed no significant differences with ages. These results indicate that chewing causes regional increases in neuronal activity in the brain, some of which are age-dependent.
The purpose of this study is to investigate human brain activity during mastication using fMRI. Twelve right-handed normal subjects performed two tasks: chewing of gum at their own pace, and imitating the movements of chewing gum. In order to reveal which areas of the brain are more strongly activated while chewing gum, we performed the conjunction analyses of gum chewing minus sham chewing with gum chewing minus rest. The common activity in the orofacial sensorimotor and premotor cortex was subtracted out since it was common to both tasks, but there were some differences in activity in some prefrontal and posterior parietal cortex areas. Our results suggest that a fronto-parietal network for mastication exists and may contribute to higher cognitive information processing.
Recent research in attention has involved three networks of anatomical areas that carry out the functions of orienting, alerting and executive control (including conflict monitoring). There have been extensive cognitive and neuroimaging studies of these networks in adults. We developed an integrated Attention Network Test (ANT) to measure the efficiency of the three networks with adults. We have now adapted this test to study the development of these networks during childhood. The test is a child-friendly version of the flanker task with alerting and orienting cues. We studied the development of the attentional networks in a cross-sectional experiment with four age groups ranging from 6 through 9 (Experiment 1). In a second experiment, we compared children (age 10 years) and adult performance in both child and adults versions of the ANT. Reaction time and accuracy improved at each age interval and positive values were found for the average efficiency of each of the networks. Alertness showed evidence of change up to and beyond age 10, while conflict scores appear stable after age seven and orienting scores do not change in the age range studied. A final experiment with forty 7-year-old children suggested that children like adults showed independence between the three networks under some conditions.
In a study published previously in this journal (Wilkinson et al., 2002), the effect of chewing gum on cognitive functioning was examined. The results of this study indicated that chewing a piece of gum results in an improvement of working memory and of both immediate and delayed recall of words but not of attention. In the present study, memory and a variety of attentional functions of healthy adult participants were examined under four different conditions: no chewing, mimicking chewing movements, chewing a piece of tasteless chewing gum and chewing a piece of spearmint flavoured chewing gum. The sequence of conditions was randomised across participants. The results showed that the chewing of gum did not improve participants' memory functions. Furthermore, chewing may differentially affect specific aspects of attention. While sustained attention was improved by the chewing of gum, alertness and flexibility were adversely affected by chewing. In conclusion, claims that the chewing a gum improves cognition should be viewed with caution.
This study tests the hypothesis that chewing gum leads to cognitive benefits through improved delivery of glucose to the brain, by comparing the cognitive performance effects of gum and glucose administered separately and together. Participants completed a battery of cognitive tests in a fully related 2 x 2 design, where one factor was Chewing Gum (gum vs. mint sweet) and the other factor was Glucose Co-administration (consuming a 25 g glucose drink vs. consuming water). For four tests (AVLT Immediate Recall, Digit Span, Spatial Span and Grammatical Transformation), beneficial effects of chewing and glucose were found, supporting the study hypothesis. However, on AVLT Delayed Recall, enhancement due to chewing gum was not paralleled by glucose enhancement, suggesting an alternative mechanism. The glucose delivery model is supported with respect to the cognitive domains: working memory, immediate episodic long-term memory and language-based attention and processing speed. However, some other mechanism is more likely to underlie the facilitatory effect of chewing gum on delayed episodic long-term memory.
Two experiments examined whether chewing spearmint gum can affect the initial learning or subsequent recall of a word list. Comparing those participants in Experiment 1 who chewed gum at the learning or the recall phases showed that chewing gum at initial learning was associated with superior recall. In addition, chewing gum led to context-dependent effects as a switch between gum and no gum (or no gum and gum) between learning and recall led to poorer performance. Experiment 2 provided evidence that sucking gum was sufficient to induce some of the same effects as chewing.
The separation of concurrent sounds is paramount to human communication in everyday settings. The primary auditory cortex and the planum temporale are thought to be essential for both the separation of physical sound sources into perceptual objects and the comparison of those representations with previously learned acoustic events. To examine the role of these areas in speech separation, we measured brain activity using event-related functional Magnetic Resonance Imaging (fMRI) while participants were asked to identify two phonetically different vowels presented simultaneously. The processing of brief speech sounds (200 ms in duration) activated the thalamus and superior temporal gyrus bilaterally, left anterior temporal lobe, and left inferior temporal gyrus. A comparison of fMRI signals between trials in which participants successfully identified both vowels as opposed to when only one of the two vowels was recognized revealed enhanced activity in left thalamus, Heschl's gyrus, superior temporal gyrus, and the planum temporale. Because participants successfully identified at least one of the two vowels on each trial, the difference in fMRI signal indexes the extra computational work needed to segregate and identify successfully the other concurrently presented vowel. The results support the view that auditory cortex in or near Heschl's gyrus as well as in the planum temporale are involved in sound segregation and reveal a link between left thalamo-cortical activation and the successful separation and identification of simultaneous speech sounds.
Alerting, orienting, and executive control are widely thought to be relatively independent aspects of attention that are linked to separable brain regions. However, neuroimaging studies have yet to examine evidence for the anatomical separability of these three aspects of attention in the same subjects performing the same task. The attention network test (ANT) examines the effects of cues and targets within a single reaction time task to provide a means of exploring the efficiency of the alerting, orienting, and executive control networks involved in attention. It also provides an opportunity to examine the brain activity of these three networks as they operate in a single integrated task. We used event-related functional magnetic resonance imaging (fMRI) to explore the brain areas involved in the three attention systems targeted by the ANT. The alerting contrast showed strong thalamic involvement and activation of anterior and posterior cortical sites. As expected, the orienting contrast activated parietal sites and frontal eye fields. The executive control network contrast showed activation of the anterior cingulate along with several other brain areas. With some exceptions, activation patterns of these three networks within this single task are consistent with previous fMRI studies that have been studied in separate tasks. Overall, the fMRI results suggest that the functional contrasts within this single task differentially activate three separable anatomical networks related to the components of attention.
Chewing has been shown to alleviate feelings of sleepiness and improve cognitive performance during the day. This study investigated the effect of chewing on alertness and cognitive performance across one night without sleep as well as the possible mediating role of cardiac autonomic activity. Fourteen adults participated in a randomized, counterbalanced protocol employing a chewing, placebo and caffeine condition. Participants completed tasks assessing psychomotor vigilance, tracking, grammatical reasoning, alertness and sleepiness each hour across the night. All participants received either placebo or caffeine (200 mg), while the chewing condition also chewed on a tasteless and odorless substance for 15 min each hour. Heart rate (HR), root mean square of the successive differences in R-R intervals on the ECG (RMSSD), and preejection period (PEP) were simultaneously recorded. Alertness and cognitive performance amongst the chewing condition did not differ or were in fact worse when compared with placebo. Similarly, measures of HR and RMSSD remained the same between these two conditions; however, PEP was reduced in the later part of the night in the chewing condition compared with a relative increase for placebo. Caffeine led to improved speed and accuracy on cognitive tasks and increased alertness when compared with chewing. Relative increases in RMSSD and reductions in HR were demonstrated following caffeine; however, no change in PEP was seen. Strong associations between cardiac parasympathetic activity and complex cognitive tasks, as well as between subjective alertness and simpler cognitive tasks, suggest a differential process mediating complex versus simple cognitive performance during sleep deprivation.
The experiment examined the prediction that chewing gum at learning and/or recall facilitated subsequent word recall. Chewing gum at learning significantly impaired recall, indicating that the chewing of gum has a detrimental impact upon initial word encoding. In addition, a context-dependent memory effect was reported for those participants who both learned and recalled in the absence of gum; however, a context-dependent effect was not found with chewing gum. The findings contradict previous research.
To investigate the neural network involved in the control of mastication during changes in food hardness, we employed functional magnetic resonance imaging while 15 healthy subjects chewed gum whose hardness was changed by chewing. By comparing the areas activated when the hardness of the bolus varied widely with those seen when the hardness of the bolus had stabilized, we identified selective activations of the supplementary motor area, the dorsolateral prefrontal cortex, the superior temporal gyrus of the left hemisphere, and the premotor area and inferior parietal lobule of the right hemisphere. These findings indicate that these areas are probably related to processes linking sensory input and motor output involved in the change of hardness food during mastication.
Two experiments independently investigated the basis of the chewing gum induced context-dependent memory effect. At learning and/or recall, participants either chewed flavourless gum (Experiment 1) or received mint-flavoured strips (Experiment 2). No context-dependent memory effect was found with either flavourless gum or mint-flavoured strips, indicating that independently the contexts were insufficiently salient to induce the effect. This is found despite participants' subjective ratings indicating a perceived change in state following administration of flavourless gum or mint-flavoured strips. Additionally, some preliminary evidence for a non-additive facilitative effect of receiving gum or flavour at either learning and/or recall is reported. The findings raise further concerns regarding the robustness of the previously reported context-dependent memory effect with chewing gum.
It has been generally suggested that chewing produces an enhancing effect on cognitive performance-related aspects of memory by the test battery. Furthermore, recent studies have shown that chewing is associated with activation of various brain regions, including the prefrontal cortex. However, little is known about the relation between cognitive performances affected by chewing and the neuronal activity in specified regions in the brain. We therefore examined the effects of chewing on neuronal activities in the brain during a working memory task using fMRI. The subjects chewed gum, without odor and taste components, between continuously performed two- or three-back (n-back) working memory tasks. Chewing increased the BOLD signals in the middle frontal gyrus (Brodmann's areas 9 and 46) in the dorsolateral prefrontal cortex during the n-back tasks. Furthermore, there were more prominent activations in the right premotor cortex, precuneus, thalamus, hippocampus and inferior parietal lobe during the n-back tasks after the chewing trial. These results suggest that chewing may accelerate or recover the process of working memory besides inducing improvement in the arousal level by the chewing motion.
Investigation of acoustic noise on 15 MRI scanners from 0.2T to 3T
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