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Abstract

It was recently established that supplemental oxygen administration significantly enhances memory formation in healthy young adults. In the present study, a double-blind, placebo-controled design was employed to assess the cognitive and physiological effects of subjects' inspiration of oxygen or air (control) prior to undergoing simple memory and reaction-time tasks. Arterial blood oxygen saturation and heart rate were monitored during each of six phases of the experiment, corresponding to baseline, gas inhalation, word presentation, reaction time, distractor and word recall, respectively. The results confirm that oxygen administration significantly enhances cognitive performance above that seen in the air inhalation condition. Subjects who received oxygen recalled more words and had faster reaction times. Moreover, compared to participants who inhaled air, they exhibited significant hyperoxia during gas administration, word presentation, and the reaction-time task, but not at other phases of the experiment. Compared to baseline, heart rate was significantly elevated during the word presentation, reaction-time, and distractor tasks in both the air and oxygen groups. In the oxygen group, significant correlations were found between changes in oxygen saturation and cognitive performance. In the air group, greater changes in heart rate were associated with more improved cognitive performance. These results are discussed in the context of cognitive demand and metabolic supply. It is suggested that under periods of cognitive demand a number of physiological responses are brought into play that serve to increase the delivery of metabolic substrates to active neural tissue. These mechanisms can be supplemented by increased availability of circulating blood oxygen, resulting in an augmentation of cognitive performance. Heart rate reactivity and the capacity for increased blood oxygen appear to be important physiological individual differences mediating these phenomena.

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... Previous work has demonstrated that oxygen administration can improve performance on a number of cognitive measures in healthy adults (Choi et al. 2010;Chung et al. 2006Chung et al. , 2007Chung et al. , 2008aChung and Lim 2008;Chung et al. 2004a, b;Moss and Scholey 1996;Moss et al. 1998;Scholey et al. 1998Scholey et al. , 1999Sohn et al. 2005). Such improvement occurred only when concurrently measured hyperoxia coincided with encoding of target material in memory tasks, or with performance of a reaction time task (Scholey et al. , 1999. ...
... Previous work has demonstrated that oxygen administration can improve performance on a number of cognitive measures in healthy adults (Choi et al. 2010;Chung et al. 2006Chung et al. , 2007Chung et al. , 2008aChung and Lim 2008;Chung et al. 2004a, b;Moss and Scholey 1996;Moss et al. 1998;Scholey et al. 1998Scholey et al. , 1999Sohn et al. 2005). Such improvement occurred only when concurrently measured hyperoxia coincided with encoding of target material in memory tasks, or with performance of a reaction time task (Scholey et al. , 1999. These results support the idea that increased circulating oxygen is available to, and utilized by, metabolically active tissue including the neural substrates which underlie cognitive processing. ...
... Our hypotheses were partially supported. These results confirm that oxygen inspiration enhances cognitive performance (Chung et al. 2007(Chung et al. , 2008aChung and Lim 2008;Chung et al. 2004a;Moss and Scholey 1996;Moss et al. 1998;Scholey et al. 1998Scholey et al. , 1999Sohn et al. 2005;Choi et al. 2010;Chung et al. 2004bChung et al. , 2006Chung et al. , 2008b. Participants made significantly fewer errors during Serial Sevens when in the oxygen condition than when in the air condition; the effect was relatively robust with a medium effect size. ...
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Both supplemental glucose and oxygen administration can improve aspects of cognitive performance. Previous research has established that more effortful cognitive processing results in reductions in peripheral blood glucose. We hypothesized that a similar phenomenon may be evident when measuring blood oxygen levels. This double-blind, placebo (air)-controlled, crossover study examined the effects of 100% oxygen administration and mental effort on heart rate and blood oxygen saturation. In counterbalanced order, twenty participants performed tasks where cognitive demand was relatively high (Serial Sevens) and relatively low (counting upwards) under conditions of normoxia and hyperoxia. Oxygen saturation and heart rates were co-monitored using a pulse oximeter. Oxygen administration was associated with significantly fewer errors during Serial Sevens and the generation of more responses during counting. Both hyperoxia and heart rate were differentially affected by gas and task. Following oxygen inspiration, transient hyperoxia decayed significantly more rapidly during Serial Sevens than during the counting task. In the air condition, blood oxygen levels were raised during Serial Sevens compared with counting. The opposite effects were observed for heart rate. These results suggest that, following oxygen inspiration, a high cognitive load results in measurable uptake of circulating oxygen. This is likely to involve somatic and central processes.
... To sustain life, every breathing gas mixture for divers must include oxygen and divers invariably breathe oxygen at partial pressures higher than in air at one atmosphere. Hyperbaric oxygen has been postulated to cause both narcosis (Lang, 2006;Linnarsson et al., 1990), a state of cognitive impairment (Frankenhaeuser et al., 1963;Freiberger et al., 2016;Hesser et al., 1978), and hyperexcitability (Bitterman, 2004;Ciarlone et al., 2019;Rostain & Lavoute, 2016), a state of increased neuronal activity with enhanced function (Germonpré et al., 2017;Scholey et al., 1999). Some authors even suggest hyperbaric oxygen is capable of producing both states, although with a time delay of 30 min for hyperexcitability to occur as part of central nervous system (CNS) oxygen toxicity (Kot et al., 2015). ...
... Specifically, the effort scale showed large reductions associated with oxygenbreathing, and could be related to mild euphoria related to hyperoxia (Bean, 1945;Sperlich et al., 2017). Cognitive enhancement by hyperoxia has been found previously in psychometric performance tests of memory encoding and stimulus reaction (Damato et al., 2020;Scholey et al., 1999Scholey et al., , 2020. These alterations in perceived respiratory interoception could, themselves, cause changes in DMN function in a top-down phenomenon-as has been observed in meditation and free diver breath holding (Annen et al., 2021). ...
Article
Divers breathe higher partial pressures of oxygen at depth than at the surface. The literature and diving community are divided on whether or not oxygen is narcotic. Conversely, hyperbaric oxygen may induce dose‐dependent cerebral hyperexcitability. This study evaluated whether hyperbaric oxygen causes similar narcotic effects to nitrogen, and investigated oxygen's hyperexcitability effect. Twelve human participants breathed “normobaric” air and 100% oxygen, and “hyperbaric” 100% oxygen at 142 and 284 kPa, while psychometric performance, electroencephalography (EEG), and task load perception were measured. EEG was analyzed with functional connectivity and temporal complexity algorithms. The spatial functional connectivity, estimated using mutual information, was summarized with the global efficiency network measure. Temporal complexity was calculated with a “default‐mode‐network (DMN) complexity” algorithm. Hyperbaric oxygen‐breathing caused no change in EEG global efficiency or in the psychometric test. However, oxygen caused a significant reduction of DMN complexity and a reduction in task load perception. Hyperbaric oxygen did not cause the same changes in EEG global efficiency seen with hyperbaric air, which likely related to a narcotic effect of nitrogen. Hyperbaric oxygen seemed to disturb the time evolution of EEG patterns that could be taken as evidence of early oxygen‐induced cortical hyperexcitability. These findings suggest that hyperbaric oxygen is not narcotic and will help inform divers' decisions on suitable gas mixtures. Visual summary of the study. 12 participants were exposed to normobaric air and oxygen, before pressurised to 1.4 and 2.8 ATA (in random order). EEG Connectivity did not show a change, while complexity was reduced during oxygen breathing.
... This is useful, as playing video games can increase psychophysiological arousal manifesting in parameters such as heart rate variations, suggesting that the cognitive and subsequent physical load can be significant [23]. The association of cardiovascular activity with exercise and mental demand is well documented; heart rate is one of the most commonly assessed physiological parameters, and varies with both physical and cognitive exertion [24]. It is often treated as a surrogate for sympathetic activity and can be helpful to assess stress. ...
... We used Python 3.8, the BioSPPy library (0.6.1) [24] for the digital filtering and segmentation methods, in order to analyze and characterize the signal, and in order to analyze the heart rate variability (HRV) PyHRV (0.4.0) was used. The mean values and standard deviation were calculated over all subjects. ...
Article
eSports is a rapidly growing industry with increasing investment and large-scale international tournaments offering significant prizes. This has led to an increased focus on individual and team performance with factors such as communication, concentration, and team intelligence identified as important to success. Over a similar period of time, personal physiological monitoring technologies have become commonplace with clinical grade assessment available across a range of parameters that have evidenced utility. The use of physiological data to assess concentration is an area of growing interest in eSports. However, body-worn devices, typically used for physiological data collection, may constitute a distraction and/or discomfort for the subjects. To this end, in this work we devise a novel “invisible” sensing approach, exploring new materials, and proposing a proof-of-concept data collection system in the form of a keyboard armrest and mouse. These enable measurements as an extension of the interaction with the computer. In order to evaluate the proposed approach, measurements were performed using our system and a gold standard device, involving 7 healthy subjects. A particularly advantageous characteristic of our setup is the use of conductive nappa leather, as it preserves the standard look and feel of the keyboard and mouse. According to the results obtained, this approach shows 3–15% signal loss, with a mean difference in heart rate between the reference and experimental device of −1.778 ± 4.654 beats per minute (BPM); in terms of ECG waveform morphology, the best cases show a Pearson correlation coefficient above 0.99.
... Cognitive performance is related to blood oxygen saturation (e.g., [31,32]). In this context, the temperature and oxygen level in the ambient air can be influencing factors. ...
... Learners' nutrition may have an indirect effect on learning through the supply of energy to the brain. An elevated blood glucose level is associated with improvements in cognitive performance (e.g., [31]). Glucose, for example, is needed to meet the increased metabolic demands of the brain during demanding cognitive tasks. ...
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Research shows that various contextual factors can have an impact on learning. Some of these factors can originate from the physical learning environment (PLE) in this regard. When learning from home, learners have to organize their PLE by themselves. This paper is concerned with identifying, measuring, and collecting factors from the PLE that may affect learning using mobile sensing. More specifically, this paper first investigates which factors from the PLE can affect distance learning. The results identify nine types of factors from the PLE associated with cognitive, physiological, and affective effects on learning. Subsequently, this paper examines which instruments can be used to measure the investigated factors. The results highlight several methods involving smart wearables (SWs) to measure these factors from PLEs successfully. Third, this paper explores how software infrastructure can be designed to measure, collect, and process the identified multimodal data from and about the PLE by utilizing mobile sensing. The design and implementation of the Edutex software infrastructure described in this paper will enable learning analytics stakeholders to use data from and about the learners' physical contexts. Edutex achieves this by utilizing sensor data from smartphones and smartwatches, in addition to response data from experience samples and questionnaires from learners' smartwatches. Finally, this paper evaluates to what extent the developed infrastructure can provide relevant information about the learning context in a field study with 10 participants. The evaluation demonstrates how the software infrastructure can contextualize multimodal sensor data, such as lighting, ambient noise, and location, with user responses in a reliable, efficient, and protected manner.
... Cognitive demand has been suggested to cause an increase in heart rate in previous studies [43,44]. It has been proposed that this increase in the heart rate during cognitive processing is to allow increased metabolic activity in the brain [44]. ...
... Cognitive demand has been suggested to cause an increase in heart rate in previous studies [43,44]. It has been proposed that this increase in the heart rate during cognitive processing is to allow increased metabolic activity in the brain [44]. In this experiment, a significant increase in the power of the HFC is apparent with increasing cognitive demand. ...
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Previous studies have shown cognition to have an influence on accommodation. Temporal variation in the accommodative response occurs during the fixation on a stationary target. This constantly shifting response has been called accommodative micro-fluctuations (AMFs). The aim of this study is to determine the effects of increasing task cognitive demand on the ocular accommodation response. AMFs for 12 myopes and 12 emmetropes were measured under three conditions of varying cognitive demand and comprising reading of numbers (Num), simple arithmetic (SA), and complex arithmetic (CA). Fast Fourier transforms were used to analyze the different frequency band components of the AMFs. Other aspects of AMFs including root mean square accommodation values and chaos analysis was applied. A repeated measures ANOVA revealed a significant main effect of cognition in the mean power of the high frequency component (HFC) (F2,44 = 10.03, p < 0.005). Pairwise analyses revealed that these differences exist between SA and CA tasks (p < 0.005) and the Num and CA (p < 0.005) tasks with the HFC power being the highest for the CA condition. It appears that the difficulty of a task does affect active accommodation but to a lesser extent than other factors affecting accommodation.
... Для підвищення концентрації оцтової кислоти в силосі потрібне внесення гетеро ферментативних молочнокислих бактерій (наприклад, L. buchneri). Застосування комбінації молочнокислих бактерій гомо-і гетеро ферментативного типів в консервантах дозволяє досягти обох необхідних результатів найбільш оптимальним шляхом [13]. Загальним недоліком таких консервантів є те, що для їх виробництва і зберігання необхідні спеціальне обладнання та умови. ...
... It is proved that inhalation of oxygen can stimulate antioxidant systems, metabolism, optimize the parameters of homeostasis. In experimental studies was set, that tenday course of oxygen inhalations had antioxidant effect and activated energy metabolism in blood and tissues [11,13]. In the similar models with severe systemic pathology also was proved positive metabolic effects of oxygen [6,8,9]. ...
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В статье пишется о проблеме деградации почв в южных горных районах республики Узбекистан и охраны почв от эрозии, а также влияние эрозии на агрохимические и химические свойства типичных и темных сероземов. Целью исследований является изучение изменения агрохимических свойств почв под действием водной эрозии в предгорных, горных условиях с учетом элементов склона и экспозиции склонов. Для решение этих задач учитываться распределении разных типов севооборотов и применение минимальной обработки почв на богарных землях и на крутизне склонов непременно должна проектировании системы противоэрозионных мероприятий.
... Moreover, the body in activity increases oxygen availability to the brain, but like with glucose, if exercise is strenuous, this can turn into a reduction (Dempsey et al., 1984;Subudhi et al., 2008). Extra oxygen, like extra glucose, also appears to enhance cognition (Chung et al., 2006;Scholey, Moss, Neave, & Wesnes, 1999) such as reaction times and word memory (Scholey et al., 1999), and verbal cognition (Chung et al., 2006), but see negative findings for working and long-term memory (Andersson, Berggren, Gronkvist, Magnusson, & Svensson, 2002). Reduced oxygen both by experiment and by high altitude (as with reduced glucose) can impair cognitive performance (Bartholomew et al., 1999;Virues-Ortega, Buela-Casal, Garrido, & Alcazar, 2004). ...
... Moreover, the body in activity increases oxygen availability to the brain, but like with glucose, if exercise is strenuous, this can turn into a reduction (Dempsey et al., 1984;Subudhi et al., 2008). Extra oxygen, like extra glucose, also appears to enhance cognition (Chung et al., 2006;Scholey, Moss, Neave, & Wesnes, 1999) such as reaction times and word memory (Scholey et al., 1999), and verbal cognition (Chung et al., 2006), but see negative findings for working and long-term memory (Andersson, Berggren, Gronkvist, Magnusson, & Svensson, 2002). Reduced oxygen both by experiment and by high altitude (as with reduced glucose) can impair cognitive performance (Bartholomew et al., 1999;Virues-Ortega, Buela-Casal, Garrido, & Alcazar, 2004). ...
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1. After weaning, human hunter-gatherer juveniles receive substantial (≈3.5-7 MJ day^-1^), extended (≈15 years) and reliable (kin and nonkin food pooling) energy provision.2. The childhood (pediatric) and the adult human brain takes a very high share of both basal metabolic rate (BMR) (child: 50-70%; adult: ≈20%) and total energy expenditure (TEE) (child: 30-50%; adult: ≈10%).3. The pediatric brain for an extended period (≈4-9 years-of-age) consumes roughly 50% more energy than the adult one, and after this, continues during adolescence, at a high but declining rate. Within the brain, childhood cerebral gray matter has an even higher 1.9 to 2.2-fold increased energy consumption. 4. This metabolic expensiveness is due to (i) the high cost of synapse activation (74% of brain energy expenditure in humans), combined with (ii), a prolonged period of exuberance in synapse numbers (up to double the number present in adults). Cognitive development during this period associates with volumetric changes in gray matter (expansion and contraction due to metabolic related size alterations in glial cells and capillary vascularization), and in white matter (expansion due to myelination). 5. Amongst mammals, anatomically modern humans show an unique pattern in which very slow musculoskeletal body growth is followed by a marked adolescent size/stature spurt. This pattern of growth contrasts with nonhuman primates that have a sustained fast juvenile growth with only a minor period of puberty acceleration. The existence of slow childhood growth in humans has been shown to date back to 160,000 BP. 6. Human children physiologically have a limited capacity to protect the brain from plasma glucose fluctuations and other metabolic disruptions. These can arise in adults, during prolonged strenuous exercise when skeletal muscle depletes plasma glucose, and produces other metabolic disruptions upon the brain (hypoxia, hyperthermia, dehydration and hyperammonemia). These are proportional to muscle mass.7. Children show specific adaptations to minimize such metabolic disturbances. (i) Due to slow body growth and resulting small body size, they have limited skeletal muscle mass. (ii) They show other adaptations such as an exercise specific preference for free fatty acid metabolism. (iii) While children are generally more active than adolescents and adults, they avoid physically prolonged intense exertion. 8. Childhood has a close relationship to high levels of energy provision and metabolic adaptations that support prolonged synaptic neurodevelopment.
... Altogether, our results suggest a physiologic mechanism of CMRO 2 as a resource affording cognitive abilities (Scholey et al., 1999). For example, in a healthy system, during periods of cognitive demand, physiologic responses lead to increased oxygen delivery and metabolism in neural tissue, allowing efficient cognitive performance (Attwell et al., 2010;Cauli and Hamel, 2010). ...
Article
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Background Cerebral metabolic rate of oxygen (CMRO2), a measure of global oxygen metabolism, reflects resting cellular activity. The mechanisms underlying fatigue and cognitive dysfunction in multiple sclerosis (MS) remain unknown. If fatigue indeed reflects ongoing autoimmune activity and cortical reorganization, and cognitive decline is the result of gray matter atrophy and white matter degeneration, we postulate that changes in CMRO2 should reflect disease activity and predict these symptoms. Objective We sought to utilize T2-Relaxation-Under-Spin-Tagging (TRUST) and phase-contrast (PC) MRI to measure global CMRO2 to understand its relationships to white matter microstructure, fatigue and cognitive dysfunction. Methods We measured venous oxygenation (TRUST) and cerebral blood flow (PC-MRI) in superior sagittal sinus to calculate global CMRO2 and diffusion tensor imaging (DTI) to evaluate white matter microstructure in healthy controls (HC) and MS patients. Participants underwent neuropsychological examinations including Modified Fatigue Impact Scale (MFIS) and Symbol-Digit-Modalities Test (SDMT). Results We observed lower CMRO2 in MS patients compared to HC. After controlling for demographic and disease characteristics (i.e., age, education, disability, lesion volume), CMRO2 predicted increased fatigue (MFIS) and reduced cognitive performance (SDMT) in MS patients. Finally, MS patients with higher CMRO2 have reduced FA in normal-appearing white-matter. Conclusion Altogether, these results suggest that increased CMRO2 reflects ongoing demyelination and autoimmune activity which plays an important role in both fatigue and cognitive dysfunction.
... Concerning the administration of oxygen, beneficial effects of hyperoxia on cognitive performance have been shown repeatedly (Chung et al., 2007(Chung et al., , 2006(Chung et al., , 2004Scholey, Moss, Neave, & Wesnes, 1999). Moreover, higher oxygen levels not only can lead to improved performance, but they were also found to effect increased activation of task-relevant brain areas within the same persons measured via fMRI in different experimental oxygen concentration conditions (Chung et al., 2007(Chung et al., , 2006(Chung et al., , 2004. ...
Thesis
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Die vorliegende kumulative Dissertation erarbeitet eine aktualisierte Interpretation von IQ-Werten, die auf vier zentralen Ebenen erfolgt: (1) Die strukturell-messtheoretische Ebene, (2) die neurobiologische Ebene, (3) die Interpretation als Lernindikator sowie (4) die Perspektive ressourcenbasierter dynamischer Systeme. Jeder Ebene entspricht ein Kapitel der Arbeit, dessen Hauptbestandteil jeweils eine entsprechende Publikation ist. Hauptbestandteil von Kapitel 1 ist die Publikation „Reliability and interpretation of total scores from multidimensional cognitive measures—Evaluating the GIK 4–6 using bifactor analysis“ (Debatin, Aljughaiman, Alghawi, Stoeger & Ziegler, 2018), die sich mit der Zuordnung und Quantifizierung von Varianzanteilen in Gesamtwerten von Testverfahren mit multidimensionaler Faktorenstruktur beschäftigt. Kapitel 1 kommt zu dem Schluss, dass IQ-Werte als je nach Testbatterie mehr oder weniger guter Schätzer des g-Faktors gesehen werden sollten. Die testspezifische Sättigung mit dem g-Faktor ist quantifizierbar und sollte routinemäßig ermittelt werden. Die meisten bisher überprüften gängigen Testbatterien weisen eine sehr hohe Sättigung auf und sind daher als gute Schätzer des g-Faktors interpretierbar. Dies verlagert die Interpretations-problematik von IQ-Werten auf die Interpretation des g-Faktors. Hauptbestandteil von Kapitel 2 ist die Publikation „A revised mental energy hypothesis of the g factor in light of recent neuroscience” (Debatin, 2019), die sich aus einer neurobiologischen Perspektive mit der Interpretation des g-Faktors auseinandersetzt. Der g-Faktor wird als das Resultat interindividueller Unterschiede in personenspezifischen biologischen Faktoren – insbesondere der Funktionsfähigkeit des Energiestoffwechsels und der damit verbundenen neuronalen Plastizität – sowie als das Resultat interindividueller Unterschiede in Umweltvariablen und der lebenslangen Interaktion dieser Faktoren miteinander gesehen. Der gleiche Gesamtwert in Intelligenztests kann demnach je nach Person zu unterschiedlichem Ausmaß durch Umweltfaktoren bedingt sein. Hauptbestandteil von Kapitel 3 ist die Publikation „Does fluid intelligence facilitate the learning of English as a foreign language?—A longitudinal latent growth curve analysis” (Debatin, Harder & Ziegler, 2019), die sich theoretisch und empirisch durch den Einsatz eines latenten Wachstumskurvenmodells mit einem zentralen Aspekt von Intelligenzdefinitionen auseinandersetzt: der Annahme, dass Intelligenz mit einer erhöhten generellen Lernfähigkeit einhergeht. Basierend auf dem aktuellen Stand empirischer Befunde kommt Kapitel 3 zu dem Schluss, dass IQ-Werte, auch aus Testbatterien fluider Intelligenz, entgegen ursprünglicher Annahmen kein starker Prädiktor der Lerngeschwindigkeit über einen längeren Zeitraum sind; zudem sind IQ-Werte selbst das Ergebnis von Lernprozessen, die durch eine Vielzahl von Faktoren beeinflusst werden. Es wird postuliert, dass die in Kapitel 2 diskutierte Funktions-fähigkeit des Energiestoffwechsels und die damit verbundene neuronale Plastizität direktere und bessere Indikatoren einer Potentialkomponente sind. Hauptbestandteil von Kapitel 4 ist die Publikation „Learning resources and talent development from a systemic point of view“ (Ziegler, Debatin & Stoeger, 2019), die eine Einführung in das Aktiotop-Modell der Begabung (Ziegler, 2005), ein ressourcenbasiertes Dynamisches-System-Modell der Talententwicklung, gibt und empirisch den Zusammenhang zwischen internalen und externalen Ressourcen und Leistung in drei verschiedenen Domänen zeigt. Zusätzlich wird der Zusammenhang zwischen Ressourcen und IQ-Werten ermittelt und diskutiert. Kapitel 4 präzisiert die Annahmen zur Entstehung des g-Faktors und der Vorgänge in Lernverläufen durch das Aufgreifen von Ansätzen ressourcenbasierter dynamischer Systeme. Interindividuelle Unterschiede in IQ-Werten und des g-Faktors werden als das Ergebnis interindividueller Unterschiede in der Summe internaler und externaler Ressourcen und den mannig-faltigen reziproken Prozessen im Laufe der Entwicklung gesehen. Zusammenfassend kommt die Dissertation zu dem Ergebnis, dass zwischen IQ-Werten und der breit akzeptierten Konsensdefinition von Intelligenz (Gottfredson, 1997) nur teilweise Überschneidungen bestehen und zentrale Aspekte dieser Definition nicht, oder nur sehr unzureichend, durch IQ-Werte erfasst werden. Dies widerspricht der gängigen Annahme, dass IQ-Werte gute Schätzer einer generellen Intelligenz sind. Es wird eine moderatere Interpretation als aktuelle Ausprägung eines praktisch relevanten Grundrepertoires der in einer Gesellschaft geforderten und geschätzten basalen kognitiven Fertigkeiten vertreten.
... Use of heart rate to indicate engagement in a mental task has been studied for some time and correlates closely with independent measurements such as pupil size and skin resistance [32][33]. Subsequent studies have confirmed that heart rate and engagement in a task are closely correlated, with HR increasing during the superior learning performance [34]. In addition, increased heart rate correlates with greater cognitive effort and higher-order problem solving [22,[35][36][37], with the difference in heart rate between engaged/high effort and low cognitive engagement being about 5 bpm [22]. ...
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Heart rate can be used as a measure of cognitive engagement. We measured average student heart rates during medical school lecture classes using wristwatch-style monitors. Analysis of 42 classes showed a steady decline in heart rate from the beginning to end of a lecture class. Active learning sessions (peer-discussion based problem solving) resulted in a significant uptick in heart rate, but this returned to the average level immediately following the active learning period. This is the first statistically robust assessment of changes in heart rate during the course of college lecture classes and indicates that personal heart rate monitors may be useful tools for assessment of different teaching modalities. The key findings suggest that the value of active learning within the classroom resides in the activity itself and not in an increase in engagement or reset in attention during the didactic period following an active learning session.
... As such, several studies have already investigated altered physics, optics, and elevated partial gas pressure on both physiology and psychology in submerged humans. It is thus well-known that submersion can affect cognitive performance (Dalecki, Bock, & Schulze, 2012;Steinberg & Doppelmayr, 2018), with increased oxygen and nitrogen partial-pressure causing both beneficial and detrimental effects (Balestra, Lafère, & Germonpré, 2012;Brebeck et al., 2017;Scholey, Moss, Neaven, & Wesnes, 2006). Changes in gravity can also influence cognitive performance (Brümmer et al., 2011;Manzey, Lorenz, & Poljakov, 1998;Shields, Sazma, & Yonelinas, 2016). ...
Article
Objective The intact cognitive processing capacity in highly demanding and dynamically changing situations (e.g., in extreme environmental conditions) is of central relevance for personal safety. This study therefore investigated whether underwater physical exercise (PE) affected cognitive performance by comparing these effects during underwater fin-swimming as opposed to inactivity under normal environmental conditions. Background Although acute bouts of PE can modulate cognitive performance under highly controlled and standardized laboratory conditions, no previous study has determined whether PE acutely modulates cognitive performance in non-laboratory testing conditions involving extreme environments (e.g., underwater). Method A total of 27 healthy volunteers (16 males and 11 females; 28.9 ± 7.4 years of age) participated in two experiments involving either moderate or high PE intensity. A PRE/POST crossover design was employed among participants while performing cognitive tests in a counterbalanced order (i.e., before and after 20 min of PE in submersion [WET] and once before and after inactivity [DRY] while in the laboratory). Cognitive performance was measured as a combination of executive functions through the Eriksen Flanker (inhibition) and Two-Back (working memory) Tasks using an underwater tablet computer. Results ANOVAs revealed enhanced reaction times only in the Flanker test after moderate PE for the WET condition. No other effects were detected. Conclusion These findings indicate that cognitive performance is exercise-intensity-dependent with enhanced effects during moderate PE, even in extreme environments (i.e., underwater). Application These results should be relevant in recreational and occupational contexts involving underwater activity and may also apply to microgravity (e.g., during extra-vehicular activities). Description This study compared the acute effects of physical exercise (PE) on cognitive performance in an underwater environment while participants fin-swam with SCUBA (self-contained underwater breathing apparatus) gear. Findings revealed that 20 min of moderate PE positively affected cognitive performance (i.e., inhibitory control ability). However, no changes were observed after high-intensity exercise.
... move away from teacher-directed whole-group instruction to create learner-centred workplaces for a collaborative culture of students at work (Pearlman, 2010); 2. activate the learning process and induce physical activity, which has a positive effect on memory by providing extra oxygen to the brain. It was recently established that supplemental oxygen administration significantly enhances memory formation in healthy young adults (Scholey, Moss, Neave & Wesnes, 1999); 3. use the organic design of the room and connect a child with the environment (natural light, air quality, optimal levels of colour, sound and temperature) creating a sense of security (Barrett P., Zhang, Davies & Barrett, L., 2015). ...
... Experimental studies have demonstrated that the facilitating effects of normobaric hyperoxia on nerve conduction are likely related to an enhanced production of reactive oxygen species (Brerro-Saby et al. 2010). Several reports have demonstrated that short-term normobaric oxygen (NBO) (maximum 1.0 ATA O2) positively influenced cognitive abilities, such as memory, visuospatial and verbal abilities (Moss and Scholey 1996;Moss et al. 1998;Scholey et al. 1998Scholey et al. , 1999Chung et al. 2006) and functional magnetic resonance (fMRI) studies have demonstrated that normobaric hyperoxia (NBO, 0.3 ATA O2) during verbal or visual tasks increases the activation of brain areas associated with cognitive processing (Choi et al. 2010). Kot et al. (2015) examined the effect of oxygen on neuronal excitability using CFFF in a hyperbaric environment and demonstrated a dosedependent effect. ...
... A double-blind, placebo-controlled study implied improvement in cognitive performance following oxygen administration. 27 Previous studies evaluating the association between anemia and dementia have been performed in general 16 21 22 25 or specific population, such as patients with chronic kidney disease (CKD) 23 or in older adults, 17-20 24 but data on the relationship between anemia and the risk of incident dementia in patients with type 2 diabetes are limited. Anemia frequently occurs in patients with type 2 diabetes, 28 and previous study reported that the risk of anemia in patients with diabetes is approximately two to three times higher than that of a general population. ...
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Introduction This study aimed to examine the association between anemia and the incidence of dementia in patients with new-onset type 2 diabetes. Research design and methods This study used the Korean National Health Insurance Service-Health Screening Cohort and included 32 590 participants aged ≥40 years who were diagnosed with new-onset type 2 diabetes between 2004 and 2007 and followed up until 2013. Anemia was defined according to the criteria provided by the WHO, hemoglobin <120 g/L for women and <130 g/L for men, and was measured from after diagnosis date of type 2 diabetes to 2007. Dementia was defined by the Classification of Diseases 10th revision code as primary diagnosis and was measured from after hemoglobin measurement to 2013. We calculated the adjusted HR (AHR) and 95% CI to assess the risk of dementia using multivariable Cox proportional hazards regression models. Results We identified 1682 patients who developed dementia within a 7.5-year follow-up. Among patients with type 2 diabetes, patients with anemia were associated with an increased risk of dementia than those without anemia (AHR, 1.21; 95% CI 1.06 to 1.39). Patients with mild (AHR, 1.18; 95% CI 1.03 to 1.38) and moderate (AHR, 1.39; 95% CI 1.06 to 1.83) anemia were associated with an increased risk of dementia than those without anemia among patients with type 2 diabetes. Men (AHR, 1.47; 95% CI 1.16 to 1.83) and middle-aged adults (AHR, 1.31; 95% CI 1.03 to 1.75) with anemia were associated with an increased risk of dementia than their counterparts without anemia among patients with type 2 diabetes. Conclusions Our findings suggest that anemia is significantly associated with an increased risk of dementia among patients with newly diagnosed type 2 diabetes.
... Concerning the administration of oxygen, beneficial effects of hyperoxia on cognitive performance have been shown repeatedly (Chung et al., 2004(Chung et al., , 2006(Chung et al., , 2007Scholey, Moss, Neave, & Wesnes, 1999). Moreover, higher oxygen levels not only can lead to improved performance, but they were also found to effect increased activation of task-relevant brain areas within the same persons measured via fMRI in different experimental oxygen concentration conditions (Chung et al., 2004(Chung et al., , 2006(Chung et al., , 2007. ...
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The article proposes a revised mental energy hypothesis for the emergence of the g factor. Charles E. Spearman interpreted the g factor as a kind of domain-general mental energy. Nowadays, it is known that the energy currency of organisms is the chemical energy transporter adenosine triphosphate (ATP). ATP is produced by complex metabolic processes (mainly by glucose oxidation), and most of it in the human brain is used for neural signaling. There are substantial individual differences in the metabolic properties of the brain, which lead to different levels of energy production. It is thereby proposed to place more emphasis on individual differences of metabolic functions in intelligence research. Neuroscientific findings suggest that increased brain metabolism and, therefore, higher energy-production levels facilitate better performance on different cognitive tasks. These findings are not in conflict with the refined neural efficiency hypothesis. In addition, building on Dennis Garlick’s proposal that neural plasticity is the core process underlying the development of the g factor, it is illustrated why ATP is crucial for neural plasticity. Taken together, the direct effects of level of energy production on cognitive performance and the relations with neural plasticity suggest an important role in the emergence of the g factor.
... Experimental studies have demonstrated that the facilitating effects of normobaric hyperoxia on nerve conduction are likely related to an enhanced production of reactive oxygen species (Brerro-Saby et al. 2010). Several reports have demonstrated that short-term normobaric oxygen (NBO) (maximum 1.0 ATA O2) positively influenced cognitive abilities, such as memory, visuospatial and verbal abilities (Moss and Scholey 1996;Moss et al. 1998;Scholey et al. 1998Scholey et al. , 1999Chung et al. 2006) and functional magnetic resonance (fMRI) studies have demonstrated that normobaric hyperoxia (NBO, 0.3 ATA O2) during verbal or visual tasks increases the activation of brain areas associated with cognitive processing (Choi et al. 2010). Kot et al. (2015) examined the effect of oxygen on neuronal excitability using CFFF in a hyperbaric environment and demonstrated a dosedependent effect. ...
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Purpose Underwater divers face several potential neurological hazards when breathing compressed gas mixtures including nitrogen narcosis which can impact diver’s safety. Various human studies have clearly demonstrated brain impairment due to nitrogen narcosis in divers at 4 ATA using critical flicker fusion frequency (CFFF) as a cortical performance indicator. However, recently some authors have proposed a probable adaptive phenomenon during repetitive exposure to high nitrogen pressure in rats, where they found a reversal effect on dopamine release. Methods Sixty experienced divers breathing Air, Trimix or Heliox, were studied during an open water dive to a depth of 6 ATA with a square profile testing CFFF measurement before (T0), during the dive upon arriving at the bottom (6 ATA) (T1), 20 min of bottom time (T2), and at 5 m (1.5 ATA) (T3). Results CFFF results showed a slight increase in alertness and arousal during the deep dive regardless of the gas mixture breathed. The percent change in CFFF values at T1 and T2 differed among the three groups being lower in the air group than in the other groups. All CFFF values returned to basal values 5 min before the final ascent at 5 m (T3), but the Trimix measurements were still slightly better than those at T0. Conclusions Our results highlight that nitrogen and oxygen alone and in combination can produce neuronal excitability or depression in a dose-related response.
... Recently, research has begun focussing on the role that exercise-induced changes in cerebral blood flow and oxygenation may play in concurrent cognitive performance. Cognitive performance diminishes during hypoxia (e.g., Fowler et al. 1987;Turner et al. 2015), but is facilitated during hyperoxia (e.g., Chung et al. 2007;Scholey et al. 1999). A number of studies now have examined exercise, cognitive performance and prefrontal cerebral haemodynamics, as measured by oxygenated haemoglobin (O 2 Hb), simultaneously, with divergent findings reported (Ando et al. 2011;Schmit et al. 2015;Tempest et al. 2017). ...
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Introduction: Studies of cerebral haemodynamics have shown changes with increased exercise intensity, but the patterns have been highly variable and reliable associations with cognitive performance have not been identified. The aim of this study was to examine whether exercise-induced changes in oxygenated haemoglobin (O2Hb) led to changes in concomitant cognitive performance. Methods: This study examined cardiorespiratory and cerebral haemodynamics during multi-stage exercise from rest to exhaustion, with (Ex + C) and without (Ex) concurrent cognitive performance (Go/No-go task). Results: The presence of the cognitive task affected both cardiorespiratory and cerebral haemodynamics. The patterns in the cerebral haemodynamics during Ex and Ex + C diverged above the respiratory compensation threshold (RCT), but differences were significant only at 100% [Formula: see text], displaying increased deoxygenated haemoglobin (HHb), decreased difference between oxygenated and deoxygenated haemoglobin (HbDiff), and decreased cerebral oxygenation (COx) during Ex + C. More complex haemodynamic trends against intensity during Ex + C suggested that the presence of a cognitive task increases cerebral metabolic demand at high exercise intensities. The levels of O2Hb, HHb, HbDiff and total haemoglobin increased most steeply at intensities around the RCT during both Ex and Ex + C, but these changes were not accompanied by improved cognitive performance. Conclusion: The primary hypothesis, that cognitive performance would match changes in O2Hb, was not supported. Small variations in reaction time and response accuracy across exercise intensities were not significant, suggesting that cognitive performance is unaffected by intense short-duration exercise. Our results add further evidence that exercise-induced changes in cerebral haemodynamics do not affect cognitive performance.
... This pattern is coherent with finding of Samuelson et al. (2008), who showed that verbal learning and recall improved in follow-up testing of two cases one year after the drowning event, while the working memory deficit remained. The findings indicate that memory is one of the cognitive functions that has been consistently reported as being affected early by the lack of or oversupply of oxygen (Asmaro, Mayall, & Ferguson, 2013;Scholey, Moss, Neave, & Wesnes, 1999). ...
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Introduction: Drowning is a serious and frequently neglected public health threat. Primary respiratory impairment after submersion often leads to brain dysfunction. Depending on the period of global hypoxia (respiratory failure), clinical aspects of neurological dysfunction are evident on the first evaluation after the water rescue. Nowadays, many neuropsychological assessments after drowning are inconclusive, with some studies reporting only minor neurological or cognitive impairments. The aim of this study is to identify measures in neuropsychological tests that most contribute to classify volunteers as moderate drowning subjects or healthy controls. To the best of our knowledge, this study is the first neuropsychological prospective case-control study of moderate drowning in a country with large coastal cities. Method: Fifteen moderate drowning patients (DP), who met the inclusion criteria, were compared with 18 healthy controls (HC). All subjects were assessed on memory, learning, visual spatial ability, executive function, attention, and general intellectual functioning and underwent structural magnetic resonance (MR) imaging of the brain at 3.0 T, in order to exclude subjects with anatomic abnormalities. Results: Neuropsychological tests assessing learning, execution function, and verbal fluency-Rey Auditory Verbal Learning Test (RAVLT) general learning ability, Digit Span total, Phonological Verbal Fluency (total FAS correct), and Brief Visuospatial Memory Test Revised (BVMT) correct recognition-have the strongest discriminating ability, using predictive models via the partial least squares (PLS) approach for data classification, while the other tests have shown similar predictive values between groups. Conclusions: Learning, execution function, and verbal fluency domains were the most critically affected domains. Serious impairments in the same domains have already been reported in severe drowning cases, and we hypothesize that subtle alterations found in moderate drowning cases, although not sufficient to be detected in daily routine, may possibly have a negative impact on cognitive reserve.
... The premise underlying this body of research is that the supplementation of these compounds will, via a multitude of mechanisms, enhance some aspect/s of cognitive function, mood and/or physical performance. Naturally these studies produce varied results with some robust results evinced from compounds such as caffeine (1) , the neural substrates oxygen (2,3) and glucose (4) and, more recently, supplementation of the water-soluble vitamins (5) . However, other supplemented compounds appear almost to elicit no cognitive benefit to the young, healthy cohorts utilised; the polyphenol resveratrol, for example (6)(7)(8) . ...
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Our current therapeutic drugs for Alzheimer's disease are predominantly derived from the alkaloid class of plant phytochemicals. These drugs, such as galantamine and rivastigmine, attenuate the decline in the cholinergic system but, as the alkaloids occupy the most dangerous end of the phytochemical spectrum (indeed they function as feeding deterrents and poisons to other organisms within the plant itself), they are often associated with unpleasant side effects. In addition, these cholinesterase inhibiting alkaloids target only one system in a disorder, which is typified by multifactorial deficits. The present paper will look at the more benign terpene (such as Ginkgo biloba, Ginseng, Melissa officinalis (lemon balm) and Salvia lavandulaefolia (sage)) and phenolic (such as resveratrol) phytochemicals; arguing that they offer a safer alternative and that, as well as demonstrating efficacy in cholinesterase inhibition, these phytochemicals are able to target other salient systems such as cerebral blood flow, free radical scavenging, anti-inflammation, inhibition of amyloid-β neurotoxicity, glucoregulation and interaction with other neurotransmitters (such as γ-aminobutyric acid) and signalling pathways (e.g. via kinase enzymes).
... These data support the findings of Gill et al., who studied resting and exercising divers at 1.3-ATA O 2 and found that it appeared to counteract CO 2 -associated impairment (42). Scholey and colleagues also found that O 2 selectively improved cognitive performance and memory consolidation (80,81 from 0.21 to 1.22 ATA was associated with an increase in motor error of 7% over baseline (P ϭ 0.003, ANOVA). When added CO 2 and exercise were present, the O 2 effect was amplified. ...
Article
Introduction: Diving narcosis results from the complex interaction of gases, activities and environmental conditions. We hypothesized these interactions could be separated into their component parts. Where previous studies have tested single cognitive tasks sequentially, we varied inspired partial pressures of CO2, N2 and. O2 in immersed, exercising subjects while assessing multi-tasking performance with the MATB-II flight simulator. Methods: Cognitive performance was tested under 20 conditions of gas partial pressure and exercise in 42 male subjects meeting US Navy age and fitness profiles. Inspired nitrogen (N2) and oxygen (O2) partial pressures were 0, 4.5 and 5.6 ATA and 0.21, 1.0, and 1.22 ATA respectively, at rest and during 100 watt immersed exercise with and without 0.075 ATA CO2 Linear regression modeled the association of gas partial pressure on task performance while controlling for exercise, hypercapnic ventilatory response, dive training, video game frequency and age. Subjects served as their own controls. Results: Impairment of memory, attention, and planning, but not motor tasks, was associated with N2 partial pressures > 4.5 ATM. Sea-level O2 at 0.925 ATA partially rescued motor and memory reaction-time impaired by 0.075ATA CO2, however, at hyperbaric pressures an unexpectedly strong interaction between CO2, N2 and exercise caused incapacitating narcosis with amnesia, which was augmented by O2 Perception of narcosis was not correlated with actual scores. Conclusions: The relative contributions of factors associated with diving narcosis will be useful to predict the effects of gas mixtures and exercise conditions on the cognitive performance of divers. The O2 effects are consistent with O2 narcosis or enhanced O2 toxicity.
... Previous studies have demonstrated a single oxygen exposure can enhance the cognitive function such as verbal function, visuospatial function through increased brain activation [22][23][24][25][26]. In a recent study, multitasking was significantly enhanced during hyperbaric oxygen exposure [27]. ...
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More than half of community-dwelling individuals sixty years and older express concern about declining cognitive abilities. The current study's aim was to evaluate hyperbaric oxygen therapy (HBOT) effect on cognitive functions in healthy aging adults.A randomized controlled clinical trial randomized 63 healthy adults (>64) either to HBOT(n=33) or control arms(n=30) for three months. Primary endpoint included the general cognitive function measured post intervention/control. Cerebral blood flow (CBF) was evaluated by perfusion magnetic resonance imaging.There was a significant group-by-time interaction in global cognitive function post-HBOT compared to control (p=0.0017). The most striking improvements were in attention (net effect size=0.745) and information processing speed (net effect size=0.788).Voxel-based analysis showed significant cerebral blood flow increases in the HBOT group compared to the control group in the right superior medial frontal gyrus (BA10), right and left supplementary motor area (BA6), right middle frontal gyrus (BA6), left middle frontal gyrus (BA9), left superior frontal gyrus (BA8) and the right superior parietal gyrus (BA7).In this study, HBOT was shown to induce cognitive enhancements in healthy aging adults via mechanisms involving regional changes in CBF. The main improvements include attention, information processing speed and executive functions, which normally decline with aging.
... We considered that practice effects may have partially contributed to our findings. However, Scholey's (Scholey et al. 1999) observation of enhanced word recall during 100% F I,O 2 , coupled with findings from other groups (Chung et al. 2007), suggest that practice or ceiling effects are not necessarily responsible. ...
Article
Extreme aviation is accompanied by ever‐present risks of hypobaric hypoxia and decompression sickness. Neuroprotection against those hazards is conferred through fractional inspired oxygen (FiO2) concentrations of 60–100% (hyperoxia). Hyperoxia reduces global cerebral perfusion (gCBF), increases reactive oxygen species within the brain and leads to cell death within the hippocampus. However, an understanding of hyperoxia's effect on cortical activity and concomitant levels of cognitive performance is lacking. This limits our understanding of whether hyperoxia could lower the brain's threshold of tolerance to physiologic stressors inherent to extreme aviation, such as high gravitational forces. This study aimed to quantify the impact of hyperoxia upon global cerebral perfusion (gCBF), cognitive performance and cortical electroencephalography (EEG). Hyperoxia evoked a rapid reduction in gCBF, yet cognitive performance and vigilance were enhanced. EEG measurements revealed enhanced alpha power, suggesting less desynchrony, within the cortical temporal regions. Collectively, this work suggests hyperoxia‐induced brain hypoperfusion is accompanied by enhanced cognitive processing and cortical arousal. Extreme aviators continually inspire hyperoxic gas to mitigate risk of hypoxia and decompression injury. This neuroprotection carries a physiologic cost: reduced cerebral perfusion (CBF). As reduced CBF may increase vulnerability to ever‐present physiologic challenges during extreme aviation, we defined the magnitude and duration of hyperoxia‐induced changes in CBF, cortical electrical activity and cognition in 30 healthy males and females. Magnetic resonance imaging with pulsed arterial spin labelling provided serial measurements of global CBF (gCBF), first during exposure to 21% inspired oxygen (FiO2) followed by a 30‐minute exposure to 100% FiO2. High‐density EEG facilitated characterization of cortical activity during assessment of cognitive performance, also measured during exposure to 21% and 100% FiO2. Acid‐base physiology was measured with arterial blood gases. We found that exposure to 100% FiO2 reduced gCBF to 63% of baseline values across all participants. Cognitive performance testing at 21% FiO2 was accompanied by increased theta and beta power with decreased alpha power across multiple cortical areas. During cognitive testing at 100% FiO2, alpha activity was less desynchronized within the temporal regions than at 21% FiO2. The collective hyperoxia‐induced changes in gCBF, cognitive performance and EEG were similar across observed partial pressures of arterial oxygen (PaO2), which ranged between 276–548 mmHg, and partial pressures of arterial carbon dioxide (PaCO2), which ranged between 34–50 mmHg. Sex did not influence gCBF response to 100% FiO2. Our findings suggest hyperoxia‐induced reductions in gCBF evoke enhanced levels of cortical arousal and cognitive processing, similar to those occurring during a perceived threat. This article is protected by copyright. All rights reserved
... The results approve that the O2 administration significantly enhances cognitive achievement more that seen in the control group. The subjects who received O2 had faster reaction times and re-called more words than the control group [7] . ...
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Background and Aims:ackground and Aim: Many factors have an impact on academic performance, cognitive function one of the most important factor which affect the academic performance, cognitive means conscious mental activity as thinking, remembering, learning or using language. The objective of the study was to assess association between the oxygen saturation level, cognitive function and academic performance of medical students. Methods: This descriptive cross-sectional study conducted between October 2016 to April 2017. Simple random sampling of 88 medical students were included in the study. A self-administrated questionnaire including factors affect the oxygen saturation levels, measurement of the oxygen saturation by pulse oximeter, and digital span test which include forward and backward test. The data from this research were analyzed using mean descriptive and inferential statistical tests, standard deviation, and t-test and ANOVA with a significance level of p < 0.05. Results: Results showed that academic performance of the students had the highest correlation with the cognitive functions (p <.05). Mean± SD of cognitive function test in male and female was (14.46±3.14, 16.75±3.22 respectively), there is statistically significance difference between male and female students (p=.002). Conclusions: Results of the study concluded that the O2 saturation level are within normal range for sample population. There is a difference between male and female students in cognitive function scores; better for female students. O2 saturation level and cognitive function have a good impact on the academic performance. Also, there is no association between the cognitive function scores and the academic performance. Key words: Medical students, Cognitive function, O2 saturation, Academic performance, Jouf.
... In fact, even NBO increases nerve conduction, this is probably related to reactive oxygen species (ROS; Brerro-Saby et al., 2010). This facilitation of nerve conduction has been shown to lead to better cognitive performance, such as memory, visuospatial, and verbal abilities (Moss and Scholey, 1996;Moss et al., 1998;Scholey et al., 1998Scholey et al., , 1999Chung et al., 2006). This excitation is thought to be a result of oxygen affecting GABA neurotransmission in multiple ways. ...
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Introduction: Cold water imposes many risks to the diver. These risks include decompression illness, physical and cognitive impairment, and hypothermia. Cognitive impairment can be estimated using a critical flicker fusion frequency (CFFF) test, but this method has only been used in a few studies conducted in an open water environment. We studied the effect of the cold and a helium-containing mixed breathing gas on the cognition of closed circuit rebreather (CCR) divers. Materials and Methods: Twenty-three divers performed an identical dive with controlled trimix gas with a CCR device in an ice-covered quarry. They assessed their thermal comfort at four time points during the dive. In addition, their skin temperature was measured at 5-min intervals throughout the dive. The divers performed the CFFF test before the dive, at target depth, and after the dive. Results: A statistically significant increase of 111.7% in CFFF values was recorded during the dive compared to the pre-dive values ( p < 0.0001). The values returned to the baseline after surfacing. There was a significant drop in the divers’ skin temperature of 0.48°C every 10 min during the dive ( p < 0.001). The divers’ subjectively assessed thermal comfort also decreased during the dive ( p = 0.01). Conclusion: Our findings showed that neither extreme cold water nor helium-containing mixed breathing gas had any influence on the general CFFF profile described in the previous studies from warmer water and where divers used other breathing gases. We hypothesize that cold-water diving and helium-containing breathing gases do not in these diving conditions cause clinically relevant cerebral impairment. Therefore, we conclude that CCR diving in these conditions is safe from the perspective of alertness and cognitive performance.
... A constant supply of oxygen is essential for normal cognitive processes, and it has been demonstrated that highly concentrated oxygen can acutely enhance cognitive performance. 4,11 Conversely, low concentrations of oxygen (i.e., hypoxia) can cause a reduction in cognitive performance. 2,13,15 This reduction in cognitive performance is a chief concern in occupations that involve duties in hypoxic environments such as aerial space or high terrestrial altitude, particularly among aircraft pilots in whom a reduction in cognitive performance can have serious and potentially fatal implications. ...
Article
INTRODUCTION: Exposure to low oxygen environments (hypoxia) can impair cognitive function; however, the time-course of the transient changes in cognitive function is unknown. In this study, we assessed cognitive function with a cognitive test before, during, and after exposure to hypoxia. METHODS: Nine participants (28 4 yr, 7 women) completed Conners Continuous Performance Test (CCPT-II) during three sequential conditions: 1) baseline breathing room air (fraction of inspired oxygen, F I o 2 0.21); 2) acute hypoxia (F I o 2 0.118); and 3) recovery after exposure to hypoxia. End-tidal gas concentrations (waveform capnography), heart rate (electrocardiography), frontal lobe tissue oxygenation (near infrared spectroscopy), and mean arterial pressure (finger photoplethysmography) were continuously assessed. RESULTS: Relative to baseline, during the hypoxia trial end-tidal (-30%) and cerebral (-9%) oxygen saturations were reduced. Additionally, the number of commission errors during the CCPT-II was greater during hypoxia trials than baseline trials (2.6 0.4 vs. 1.9 0.4 errors per block of CCPT-II). However, the reaction time and omission errors did not differ during the hypoxia CCPT-II trials compared to baseline CCPT-II trials. During the recovery CCPT-II trials, physiological indices of tissue hypoxia all returned to baseline values and number of commission errors during the recovery CCPT-II trials was not different from baseline CCPT-II trials. DISCUSSION: Oxygen concentrations were reduced (systemically and within the frontal lobe) and commission errors were increased during hypoxia compared to baseline. These data suggest that frontal lobe hypoxia may contribute to transient impairments in cognitive function during short exposures to hypoxia. Uchida K, Baker SE, Wiggins CC, Senefeld JW, Shepherd JRA, Trenerry MR, Buchholtz ZA, Clifton HR, Holmes DR, Joyner MJ, Curry TB. A novel method to measure transient impairments in cognitive function during acute bouts of hypoxia . Aerosp Med Hum Perform. 2020; 91(11):839844.
... Oxygen restriction has significant effects on cognitive function; for example, less oxygen delivery to the brain has been observed in those with memory impairments [16] [17]. Moreover, oxygen administration, through the breathing of supplemental oxygen and the associated increase in blood oxygen, has been shown to result in significantly better memory performance and reaction times [18] [19] [20] [21]. ...
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Classification of cognitive workload promises immense benefit in diverse areas ranging from driver safety to augmenting human capability through closed loop brain computer interface. The brain is the most metabolically active organ in the body and increases its metabolic activity and thus oxygen consumption with increasing cognitive demand. In this study, we explore the feasibility of in-ear SpO2 cognitive workload tracking. To this end, we preform cognitive workload assessment in 8 subjects, based on an N-back task, whereby the subjects are asked to count and remember the number of odd numbers displayed on a screen in 5 second windows. The 2 and 3-back tasks lead to either the lowest median absolute SpO2 or largest median decrease in SpO2 in all of the subjects, indicating a robust and measurable decrease in blood oxygen in response to increased cognitive workload. Using features derived from in-ear pulse oximetry, including SpO2, pulse rate and respiration rate, we were able to classify the 4 N-back task categories, over 5 second epochs, with a mean accuracy of 94.2%. Moreover, out of 21 total features, the 9 most important features for classification accuracy were all SpO2 related features. The findings suggest that in-ear SpO2 measurements provide valuable information for classification of cognitive workload over short time windows, which together with the small form factor promises a new avenue for real time cognitive workload tracking.
... Both hypoxia and hyperoxia can induce cellular oxidative stress by increased levels of reactive oxygen species, resulting in cellular damage and altered tissue functions [15,16]. Brief exposure to 100% oxygen, however, reverses hypoxia and may have immediate, short-term, cognitive benefits including improved memory and reaction time [17,18]. ...
... These components allow researchers to use the heart rate to measure more advanced factors like cognitive engagement [7,35]. Cognitive engagement can be determined through the heart rate since the exposure to stimulus or tasks activates neural mechanisms and, consequently, triggers an acceleration or deceleration in the heart rate, which has been an indicator of alertness and drowsiness [36][37][38].The advantages of using heart rate include it is noninvasive, easy, and cheap to get [33,34], experiments with heart rate are simple to set up and can be used in conjunction with other biometric measures like facial expressions and respiration [38,39]. The disadvantages associated with the heart rate are the conditions of the environment under which happen the data collection since they are challenging to eliminate, and also the response time to a stimulus is long; these two points generate more uncertainty [30,40,41]. ...
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Student engagement allows educational institutions to make better decisions regarding teaching methodologies, methods for evaluating the quality of education, and ways to provide timely feedback. Due to the COVID-19 pandemic, identifying cognitive student engagement in distance learning has been a challenge in higher education institutions. In this study, we implemented a non-self-report method assessing students’ heart rate data to identify the cognitive engagement during active learning activities. Additionally, as a supplementary tool, we applied a previously validated self-report method. This study was performed in distance learning lessons on a group of university students in Bogota, Colombia. After data analysis, we validated five hypotheses and compared the results from both methods. The results confirmed that the heart rate assessment had a statistically significant difference with respect to the baseline during active learning activities, and this variance could be positive or negative. In addition, the results show that if students are previously advised that they will have to develop an a new task after a passive learning activity (such as a video projection), their heart rate will tend to increase and consequently, their cognitive engagement will also increase. We expect this study to provide input for future research assessing student cognitive engagement using physiological parameters as a tool.
... Higher FA in the CC and bilateral frontotemporal WM indicates more efficient sensorimotor and cognitive communication between the 2 cerebral hemispheres. [34,35] Higher FA has also been shown to correlate with better functional connectivity between distant brain GM regions using resting-state functional magnetic response imaging, [36,37] and is further associated with improved cognitive function. [38,39] Significant positive impacts on both the CC and frontotemporal fasciculi are consistent with previous studies that showed PE-induced increases in FA values in the corticospinal tract, superior longitudinal fascicle, inferior longitudinal fascicle, inferior fronto-occipital fascicle, and anterior thalamic radiation In case of axial diffusivity, exercise group showed significantly smaller value in most of the bilateral frontotemporal white matter with fornix and medial thalamus and sensorimotor fibers (Fig. 2a, green color). ...
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Physical exercise leads to structural changes in the brain. However, it is unclear whether the initiation or continuous practice of physical exercise causes this effect and whether brain connectivity benefits from exercise. We examined the effect of 6 months of exercise on the brain in participants who exercise regularly (n = 25) and in matched healthy controls (n = 20). Diffusion tensor imaging brain scans were obtained from both groups. Our findings demonstrate that regular physical exercise significantly increases the integrity of white matter fiber tracts, especially those related to frontal function. This implies that exercise improves brain connectivity in healthy individuals, which has important implications for understanding the effect of fitness programs on the brains of healthy subjects.
... For example, airexposed K. marmoratus proliferates epidermal capillaries in the skin to enhance their capacity for aerial O 2 uptake [45] and increase their blood O 2 -carrying capacity [46]. Increased circulating blood O 2 has been linked with improved cognitive performance in mammals [47], but it is unclear whether similar mechanisms can improve cognition in fishes. Finally, it is important to note that fish remained relatively inactive during periods of air exposure compared with periods in water, although we observed them periodically moving overland within their acclimation containers (G.S.R. 2020, personal observation). ...
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Amphibious fishes transition between aquatic and terrestrial habitats, and must therefore learn to navigate two dramatically different environments. We used the amphibious killifish Kryptolebias marmoratus to test the hypothesis that the spatial learning ability of amphibious fishes would be altered by exposure to terrestrial environments because of neural plasticity in the brain region linked to spatial cognition (dorsolateral pallium). We subjected fish to eight weeks of fluctuating air–water conditions or terrestrial exercise before assessing spatial learning using a bifurcating T-maze, and neurogenesis in the dorsolateral pallium by immunostaining for proliferating cell nuclear antigen. In support of our hypothesis, we found that air–water fluctuations and terrestrial exercise improved some markers of spatial learning. Moreover, air–water and exercised fish had 39% and 46% more proliferating cells in their dorsolateral pallium relative to control fish, respectively. Overall, our findings suggest that fish with more terrestrial tendencies may have a cognitive advantage over those that remain in water, which ultimately may influence their fitness in both aquatic and terrestrial settings. More broadly, understanding the factors that promote neural and behavioural plasticity in extant amphibious fishes may provide insights into how ancestral fishes successfully colonized novel terrestrial environments before giving rise to land-dwelling tetrapods.
... This reduces the threat of an infection (if other measures such as a sufficient distance are practices as well) [3], [4]. A significant part of societies worldwide question scientific findings, oppose government regulations, and spread misinformation regarding the coronavirus disease 2019 (Covid- 19), its transmission, the consequence of infection, and numbers or associated deaths or intensive-care medicine capacities [5][6][7][8]. An early Twitter analysis estimated that around 25% of all tweets regarding Covid-19 contain misinformation [9]. ...
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Since the outbreak of the COVID-19 pandemic, the use of face masks is recommended to prevent droplets from traveling from one person to another. A commandment to wear masks applies in most public places to contain the widespread of the virus. Some public debates concern myths regarding risks caused by wearing a mask, like, e.g., decreased blood oxygen levels and impaired cognitive capabilities. The present, pre-registered study aims to contribute clarity by delivering a direct comparison of wearing an FFP2 (N95) respirator and wearing no mask. We focused on a demanding situation to show that cognitive efficacy and the person's state is equivalent in both conditions of a randomized-controlled cross-over study design. We measured physiological (blood oxygen saturation and heart rate variability), behavioral (parameters of performance in the task), and subjective (perceived mental load) data to substantiate our assumption as broad as possible. We analyzed data from 44 participants regarding both statistical equivalence and differences. All of the investigated dimensions showed statistical equivalence given our pre-registered equivalence boundaries. None of the dimensions showed a significant difference between wearing a mask and not wearing a mask.
Article
Drosophila melanogaster is one of the promising model organisms for investigation of human diseases such as cardiac disorders. However, intact (not dissected) Drosophila larvae have not been extensively used as models in cardiac toxicity assays due to many challenges associated with assessment of their heart activities in the intact mode (i.e., heartrate monitoring of alive larva under exposure to aqueous and gaseous reagents). These challenges include the need for precise spatiotemporal control of stimulus exposure to posterior spiracles (i.e., breathing valves) and full immobilization of larvae in favorable orientations to monitor the heart under a microscope. In this paper, we not only present a novel microfluidic device that is capable of loading, orientating and immobilizing the larva reversibly in a chip, but also demonstrate for the first time the transient effects of toxic liquids (e.g., sodium azide) and gases (e.g., oxygen and carbon dioxide) at various concentrations on the heart of intact Drosophila larvae. The results demonstrated that cardiac activity increase (with excess oxygen) or arrest (with sodium azide, carbon dioxide, or lack of oxygen) are highly dependent on the concentration of the stimuli, but heart recovery after removal of chemicals is independent of chemical concentration. The presented device can be used for investigation of biological pathways underlying these responses and also for screening of various chemicals such as pharmaceutical, toxicological, and agricultural compounds on the cardiac system of intact Drosophila melanogaster or other compatible insect models. This will open new windows of opportunity in drug discovery and toxicology applications.
Chapter
Neuroscience is a new and unfamiliar field of science for educators, yet it may hold information of great importance to the development of new teaching approaches and practices and in some cases confirm sound practice already used in classrooms. Neuroscience investigates the functions of the brain. Study of the brain reaches back to the 19th century; however, this early work was restricted to structural investigations as research was applied to brains after they were removed from bodies. It was not until the 1990s that studies were able finally to investigate brains as they functioned by using Positron Emission Tomography (PET) scans and functional Magnetic Resonance Imaging (fMRI) to plot activity in the brain. More recently, newer technologies including Diffusion Tensor Imaging (DTI) and Near Infrared Spectroscopic Imaging (NIRSI) have assisted the neural investigation of the brain as it functions. Educators have become interested in neuroscience as it begins to uncover concepts that inform learning and that potentially empower learners.
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Since the outbreak of the coronavirus disease (COVID-19), face coverings are recommended to diminish person-to-person transmission of the SARS-CoV-2 virus. Some public debates concern claims regarding risks caused by wearing face masks, like, e.g., decreased blood oxygen levels and impaired cognitive capabilities. The present, pre-registered study aims to contribute clarity by delivering a direct comparison of wearing an N95 respirator and wearing no face covering. We focused on a demanding situation to show that cognitive efficacy and individual states are equivalent in both conditions. We conducted a randomized-controlled crossover trial with 44 participants. Participants performed the task while wearing an N95 FFR versus wearing none. We measured physiological (blood oxygen saturation and heart rate variability), behavioral (parameters of performance in the task), and subjective (perceived mental load) data to substantiate our assumption as broadly as possible. We analyzed data regarding both statistical equivalence and differences. All of the investigated dimensions showed statistical equivalence given our pre-registered equivalence boundaries. None of the dimensions showed a significant difference between wearing an FFR and not wearing an FFR. Trial Registration: Preregistered with the Open Science Framework: https://osf.io/c2xp5 (15/11/2020). Retrospectively registered with German Clinical Trials Register: DRKS00024806 (18/03/2021).
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Introduction: Effects of exposure to hyperoxia (PiO2 > 105 mmHg), normoxia (PiO2 95-105 mmHg) and hypoxia (PiO2 < 95 mmHg) on simple and choice reaction performance tasks were evaluated. Methods: Ten subjects performed simple and choice reaction time tests (SRT and CRT, respectively) at ground level for 40 min (20 min normoxic, 20 min hyperoxic, randomly assigned), 3048 m (10,000 ft) for 75 min (15 min hyperoxic, 60 min hypoxic), 4572 m (15,000 ft) for 60 min (15 min hyperoxic, 45 min hypoxic), and 6096 m (20,000 ft) for 35 min (15 min hyperoxic, 20 min hypoxic). SRT and CRT tests were also conducted at ground level 1 h after normoxic rest (recovery) to assess any recovery time effect on these psychomotor tasks. Results: Total response time (TRT) significantly increased by 15 ms to 25 ms at all three altitudes for both the SRT and CRT tasks. At and below 4572 m, the performance changes were gradual over the duration of the exposures, whereas at 6096 m these changes were immediate. After 1 h, no performance decrement was measured. There was no statistical evidence that ground-level performance on these tasks was improved in hyperoxic vs. normoxic conditions. Discussion: Results suggest mild decrements in reaction time due to hypoxia may occur as low as 3048 m (10,000 ft) while hyperoxia showed no positive effect on accuracy or reaction time at ground level or higher when performing simple and choice psychomotor reaction tasks.Dart T, Gallo M, Beer J, Fischer J, Morgan T, Pilmanis A. Hyperoxia and hypoxic hypoxia effects on simple and choice reaction times. Aerosp Med Hum Perform. 2017; 88(12):1073-1080.
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The measurement of cognitive activity using physiological means such as heart rate activity is a well-established research practice. Most previous studies have concluded that elevated heart rate occurs when an individual is cognitively engaged. However, there have been very few studies focusing on the effect in a learning environment. The recent proliferation of accurate, cheap and unobtrusive wearable devices with biometric sensors presents a new opportunity to perform a relatively inexpensive, natural, large scale study on the biometric effects on students during a series of lectures. This study presents the design and results of a unique two year study of students’ heart rate activity during a series of university computer programming lectures. It benchmarks student heart rate patterns during lectures and finds that there is a significant correlation between elevated heart rates and module scores. To the best of the authors’ knowledge this type of live, natural learning environment study has not been reported before.
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Human creativity refers to the cognitive capacity to produce new and valuable information. Over a long period of time, many people have been fascinated by the question of how creativity emerges in our brain and how it can be enhanced. Recently, a growing number of studies have revealed that some types of environmental stimuli can enhance human creativity. Further, specific temporal dynamics of cognitive processes are crucial for generating creative ideas. However, how the temporal dynamics of creativity are influenced by the environment remains unclear. Through a literature review of neural and psychological research, this study aimed to elucidate the environmental settings that enhance cognitive performance. We found that each stage of the temporal dynamics of creativity may be differently correlated with neural function. Further, environmental factors may have various, and sometimes contrasting, effects on the temporal dynamics of creativity. We propose a hypothesis that the optimal environmental condition varies depending on the stages of temporal dynamics since each stage requires different cognitive processes. However, there is a need for future studies to elucidate how creativity is modulated by social conditions and the physical environment as well as whether there are differences in the ideal environment for individual and group creativity. Nonetheless, this is the first study to clarify the influence of environmental settings on the temporal dynamics of creativity from the perspective of neuroscience and psychology.
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In an increasingly complex information society, demands for cognitive functioning are growing steadily. In recent years, numerous strategies to augment brain function have been proposed. Evidence for their efficacy (or lack thereof) and side effects has prompted discussions about ethical, societal and medical implications. In the public debate, cognitive enhancement is often seen as a monolithic phenomenon. On a closer look, however, cognitive enhancement turns out to be a multifaceted concept: There is not one cognitive enhancer that augments brain function per se, but a great variety of interventions that can be clustered into biochemical, physical and behavioral enhancement strategies. These cognitive enhancers differ in their mode of action, the cognitive domain they target, the timescale they work on, their availability and side effects, and how they differentially affect different groups of subjects. Here we disentangle the dimensions of cognitive enhancement, review prominent examples of cognitive enhancers that differ across these dimensions, and thereby provide a framework for both theoretical discussions and empirical research.
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Most studies examining neurocognitive aging are based on the blood-oxygen level-dependent signal obtained during functional magnetic resonance imaging (fMRI). The physiological basis of this signal is neural-vascular coupling, the process by which neurons signal cerebrovasculature to dilate in response to an increase in active neural metabolism due to stimulation. These fMRI studies of aging rely on the hemodynamic equivalence assumption that this process is not disrupted by physiologic deterioration associated with aging. Studies of neural-vascular coupling challenge this assumption and show that neural-vascular coupling is closely related to cognition. In this review, we put forward a theory of processing speed decline in aging and how it is related to age-related neural-vascular coupling changes based on the results of studies elucidating the relationships between cognition, cerebrovascular dynamics, and aging.
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One of the most extreme ecological transitions has been the colonization of land by fishes. Moving between aquatic and terrestrial environments poses critical challenges for a number of processes, including locomotion. The focus of my PhD was to investigate how the skeletal muscle of fishes remodels in response to various forms of air-exposure (e.g., constant, fluctuating) and determine the functional implications of this plasticity. I used an amphibious killifish (Kryptolebias marmoratus) to first test the hypothesis that skeletal muscle remodelling in response to constant (28 d) air-exposure is driven by the increased oxygen availability in air. Indeed, oxygen was a driver for muscle remodeling on land, as both air-exposure and hyperoxia increased (>25%) the size of red muscle fibers in K. marmoratus. Since K. marmoratus can survive for weeks on land without food, I then questioned how fish were able to maintain their muscle integrity during prolonged periods of air-exposure (21 d). I tested the hypothesis that amphibious fishes that remain on land for weeks at a time use metabolic depression as a strategy to preserve muscle integrity. My results demonstrated that metabolic depression is important for slowing the use of endogenous energy stores by fish on land, including muscle protein. I also found that K. marmoratus seek hypoxic microhabitats during prolonged air-exposure that accentuate metabolic depression. Given the highly plastic nature of K. marmoratus muscle, I then tested the hypothesis that the scope for muscle plasticity is modulated by environmental iii conditions during early development. I found that fluctuating water-air conditions during development attenuated the scope for muscle plasticity in later life. Finally, I was interested to understand the broader role of muscle and terrestrial locomotion in facilitating land invasions by fishes. I tested the hypothesis that terrestrial exercise would improve spatial cognition in amphibious fishes, and enhance neurogenesis in the brain region linked to spatial cognition. I found that terrestrial excursions enhanced cognition in K. marmoratus, as both terrestrial exercise and air-exposure improved spatial learning abilities. Overall, my thesis integrates behavioural, morphological, and physiological perspectives to provide new insights into how amphibious fishes successfully colonize and exploit terrestrial habitats.
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Amid the rapid development of information communication technologies (ICTs), residents of future smart cities are expected to be exposed to unprecedented amounts of real-time information on a daily basis. The cognitive overload driven by an excess of complex information has become a potential issue. Nonetheless, standardized information systems are still widely used, despite individual differences in information intake. To set a foundation for the intelligent information systems of smart cities, this paper introduces methods and tools for a cognition-driven, personalized information system, which acknowledges individual differences in information preference and helps reduce the cognitive load in daily lives and at work. The proposed method includes the use of virtual reality (VR) to simulate complex tasks paired with the digital twin modeling of workers’ cognitive reactions to different information formats and contents in VR simulation. Collected data are then used to build a personal digital twins model of information-driven cognition, or Cog-DT. A human subject experiment was performed with a simulated industrial facility shutdown maintenance task as a proof of concept of Cog-DT. The latest neuroimaging technology and analysis methods were applied to model unique cognitive processes pertaining to information processing. Results indicate that cognitive activities driven by different information stimuli in the work context are distinguishable and modelable with Cog-DT methods and tools. This study is expected to contribute to digital twin literature by testing a human-centered, individual-level digital twin modeling method of cognitive activities. It also sets a preliminary foundation for developing personalized information systems for the smart cities of the future.
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Cognitive functions refer to the set of brain-based skills to execute tasks of various difficulty levels. As people spend substantial time indoors, the indoor environmental quality (IEQ) influences occupants’ cognitive functions and consequently their learning and work performance. Previous studies have commonly examined the effects of IEQ on integrated learning or work performance, rather than specific cognitive skills. The present review decomposes IEQ into five factors—indoor air quality, the thermal environment, lighting, noise, and non-light visual factors. It divided cognition into five categories—attention, perception, memory, language function, and higher order cognitive skills—to better understand the relationship between IEQ and cognition. We conducted a detailed manual review of 66 focused studies and adopted co-occurrence analysis to generate landscapes of the associations between IEQ and cognition factors by analyzing keywords and abstracts of 8133 studies. Overall, results show that poor IEQ conditions are but not always associated with reduced cognition. However, the effects of a specific IEQ factor on different cognitive functions are quite distinct. Likewise, a specific cognitive function could be affected by different IEQ factors to varying degrees. Furthermore, the results suggest extensive inconsistencies in the relevant literature, especially regarding the effects of IAQ or thermal environment on cognition. Additionally, the keyword co-occurrence analysis identified more IEQ factors and cognitive functions emerging in the recent literature. Future studies are recommended to explore the factors causing the inconsistencies that we highlight here.
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Introduction: Critical flicker fusion frequency (CFFF) has been used in various studies to measure the cognitive effects of gas mixtures at depth, sometimes with conflicting or apparently paradoxical results. This study aimed to evaluate a novel automatic CFFF method and investigate whether CFFF can be used to monitor gas-induced narcosis in divers. Methods: Three hyperbaric chamber experiments were performed: 1) Automated and manual CFFF measurements during air breathing at 608 kPa (n = 16 subjects); 2) Manual CFFF measurements during air and heliox breathing at sea level (101.3 kPa) and 608 kPa (n = 12); 3) Manual CFFF measurements during oxygen breathing at sea level, 142 and 284 kPa (n = 10). All results were compared to breathing air at sea level. Results: Only breathing oxygen at sea level, and at 284 kPa, caused a significant decrease in CFFF (2.5% and 2.6% respectively compared to breathing air at sea level. None of the other conditions showed a difference with sea level air breathing. Conclusions: CFFF did not significantly change in our experiments when breathing air at 608 kPa compared to air breathing at sea level pressure using both devices. Based on our results CFFF does not seem to be a sensitive tool for measuring gas narcosis in divers in our laboratory setting.
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Hyperbaric oxygen treatment (HBOT) has been reported to improve cerebral hypoperfusion, inflammation, and mitochondrial dysfunction, all of which have been observed in some individuals with autism spectrum disorders (ASD). In several studies, HBOT improved cerebral hypoperfusion, decreased a marker of inflammation, and did not worsen oxidative stress markers at pressures commonly used in children with ASD. Most studies of HBOT in children with ASD reported improvements in several behavioral domains, although many of these studies were not controlled. The two studies employing a control group appear to have conflicting results. However, this may have been due to different sample sizes and frequencies of HBOT sessions, with the larger study reporting improvements in several domains using a greater intensity of treatments. All studies reported that HBOT had minimal adverse events. Additional studies of HBOT in individuals with ASD are warranted to determine optimal treatment protocols.
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We report an experiment that assesses the effect of variations in memory load on brain activations that mediate verbal working memory. The paradigm that forms the basis of this experiment is the "n-back" task in which subjects must decide for each letter in a series whether it matches the one presented n items back in the series. This task is of interest because it recruits processes involved in both the storage and manipulation of information in working memory. Variations in task difficulty were accomplished by varying the value of n. As n increased, subjects showed poorer behavioral performance as well as monotonically increasing magnitudes of brain activation in a large number of sites that together have been identified with verbal working-memory processes. By contrast, there was no reliable increase in activation in sites that are unrelated to working memory. These results validate the use of parametric manipulation of task variables in neuroimaging research, and they converge with the subtraction paradigm used most often in neuroimaging. In addition, the data support a model of working memory that includes both storage and executive processes that recruit a network of brain areas, all of which are involved in task performance.
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Brain glucose uptake, oxygen metabolism, and blood flow in humans were measured with positron emission tomography, and a resting-state molar ratio of oxygen to glucose consumption of 4.1:1 was obtained. Physiological neural activity, however, increased glucose uptake and blood flow much more (51 and 50 percent, respectively) than oxygen consumption (5 percent) and produced a molar ratio for the increases of 0.4:1. Transient increases in neural activity cause a tissue uptake of glucose in excess of that consumed by oxidative metabolism, acutely consume much less energy than previously believed, and regulate local blood flow for purposes other than oxidative metabolism.
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Extensive evidence indicates that relatively modest increases in circulating glucose concentrations enhance learning and memory processes in rodents and humans. In rats, systemic injections of glucose enhance learning and memory under many conditions. When microinjected into specific brain sites, glucose has selective behavioral and pharmacological effects, with behavioral effects that are specific to the brain site injected and pharmacological effects that are largely specific to interactions with opiate agonists. Recent evidence suggests that glucose may attenuate opiate inhibition of acetylcholine release in the hippocampus. The relative safety of glucose has permitted tests of glucose effects on cognitive functions in humans. Glucose also enhances learning and memory in healthy aged humans and enhances several other cognitive functions in subjects with severe cognitive pathologies, including individuals with Alzheimer's disease and Down syndrome. Thus, increases in circulating glucose concentrations have robust and broad influences on brain functions that span many neural and behavioral measures and cross readily from rodents to humans.
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Despite numerous studies indicating that transient cerebral oxygen depletion has a detrimental effect on cognition, surprisingly little research has examined the possibility of cognitive enhancement following elevated oxygen levels in healthy adults. Here, we present evidence demonstrating that oxygen administration improves memory formation. Inhalation of oxygen immediately prior to learning a word list resulted in a significant increase in mean number of words recalled 10 min later, compared to subjects who inhaled oxygen immediately prior to recall or to controls who underwent no intervention. In a second experiment, the learning-test interval was increased to 24 h and, again, only pre-learning (but not pre-test) oxygen administration resulted in significant memory facilitation. In experiment 3, inhalation of oxygen prior to learning was compared to inhalation of compressed air, oxygen (but not compressed air) resulted in a significant increase in word recall 24 h later. In no experiment did oxygen have a significant effect on any mood item measured. We interpret these data as indicating that increased availability of cerebral oxygen facilitates cognition, including memory consolidation. The implications for the psychopharmacology of cognitive enhancement are considered in the context of cholinergic systems and neural metabolism.
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It was recently demonstrated that oxygen administration can improve performance on a simple word recall task in healthy young adults. This study was aimed at determining the impact of various durations of oxygen administration on a wider range of cognitive measures. This was achieved using the Cognitive Drug Research computerised test battery, and employing a double-blind, placebo-controlled crossover design. Over a period of 7 weeks, 20 participants were trained and subsequently assessed on the test battery under several durations of oxygen inhalation; air administered in an identical fashion served as a control. The results provided support for our earlier work in that increases were found in both immediate and delayed word recall. In addition, oxygen administration significantly improved performance on several measures of attention and vigilance. Simple reaction time, choice reaction time, digit vigilance reaction time and picture recognition reaction time were improved in a manner which depended on the duration of oxygen inspired. With the exception of word recall, no significant improvements were found for any measure of accuracy, nor were word recognition, digit memory scanning, or spatial memory improved. These results are discussed in the context of stages of information processing and are consistent with the hypothesis that cognitive performance is "fuel-limited" and can be differentially augmented by increasing the availability of the brain's metabolic resources.
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Oxygen administration coinciding with word presentation enhances word recall in humans, suggesting that elevated levels of circulating blood oxygen may be available to neural memory consolidation processes. This double-blind experiment examined the relationship between blood oxygen levels and cognitive performance when oxygen was inspired for 2 min at different times relative to a simple word recall task, forward digit span and backward digit span. Transient hyperoxia, measured by haemoglobin-bound oxygen, was evident following oxygen inspiration. Neither forward nor backward digit span was affected by oxygen administration. Word recall (12 min following word presentation) was enhanced when oxygen was administered 5 min prior to, immediately before or immediately following word presentation; but not 10 min prior to, 5 min following nor 10 min following, word presentation. These data suggest that oxygen administration can selectively enhance aspects of cognitive performance and support a hypothesis whereby supplemental blood oxygen is sequestered by neural mechanisms involved in memory consolidation.
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Fifteen male volunteers participated in a dual-task study in which the central processing load of visual memory and tracking tasks and the physical load of the tracking task were orthogonally manipulated to produce varying levels of task difficulty. Multiple modes of assessment were used to measure mental workload (MWL) across difficulty levels, including: performance, subjective, cardiovascular, and metabolic. To our knowledge, this study is the first to demonstrate metabolic change with manipulations of cognitive task difficulty; others have found only baseline-to-task changes. The relation of the metabolic demands of the task to central processing resource utilization provided support for a structural energetic model of attention that may help to explain measure dissociations. The results of the present study indicated that heart period was only sensitive to central manipulations of task difficulty that affected energetic resources. Performance and subjective MWL were sensitive to all cognitive components of the tasks. We suggest that cardiovascular measures will associate with other measures only when the manipulations of task difficulty require energetic adjustment, and would expect these measures to dissociate when energetic adjustment is not required.
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The relationship between performance on a dichotic listening task and blood glucose levels was examined. It was predicted that, if the ability of blood glucose to supply the brain with its basic fuel limits performance under conditions of cognitive demand, verbal information directed to the left hemisphere would be particularly susceptible to the level of blood glucose. Via headphones, subjects heard lists of words directed to both ears. Those receiving a glucose drink recalled more of a list of words directed to the right ear and hence the left hemisphere. In those who received a glucose drink, a fall in blood glucose during the dichotic task was associated with a right ear superiority. The pattern of findings can be explained by the assumptions that under conditions of cognitive demand the supply of glucose to the brain limits performance and that there are individual differences in the ability to efficiently take glucose from the blood stream into the brain.
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Administered complex tests of declarative memory, working memory, procedural learning, and response generation and inhibition to 27 younger adults (14 men and 13 women; aged 19–28 yrs) and 32 older adults (16 men and 16 women; aged 58–77 yrs) following ingestion of saccharin or glucose. Glucose administration (GLA) significantly enhanced performance on the declarative memory measure paragraph recall for older men and younger men whose blood glucose returned to similar levels. Younger men whose blood glucose levels were lowest 60 min after glucose ingestion showed memory deterioration. GLA did not affect paragraph recall for the other groups, nor were effects noted for any group for most other cognitive measures. Results suggest that the effects of GLA are primarily restricted to declarative memory independent of task complexity, and that age, sex, and glucoregulatory response may influence hyperglycemic memory enhancement. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
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Heart rate and blood pressure may increase or decrease, or, indeed, may exhibit no change in response to stimulation or as concomitants of the performance of various tasks. These changes themselves may be correlated, both positively and negatively, or uncorrelated. Most importantly, the direction of blood pressure and heart rate changes may reveal parasympathetic-like responses while other simultaneously recorded responses reveal sympathetic-like responses, such as digital vasoconstriction, pupillary dilation, and decrease in skin resistance. To this phenomenon, we have applied the term "directional fractionation," to imply that different fractions of the total somatic response pattern may respond in opposite directions; opposite, that is, from the point of view of the notion that autonomic "arousal" is characterized by a melange of positively correlated sympathetic-like changes. This chapter presents some new experiments concerning sensorimotor processes where they evaluate not only phasic heart rate changes but intracardiac cycle effects within the framework of their neurophysiological afferent feedback model. In several places in the chapter, as well as in an addendum to the chapter, some recent criticisms that have been directed at the afferent model are discussed. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
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The present study was conducted to determine the degree to which impairments in attention accompany the memory deficits produced by scopolamine. Eighteen healthy young volunteers received scopolamine 0·6 mg subcutaneously on three experimental sessions and placebo on three others. On each session, prior to, and 60 min after injection, the subjects underwent an automated computerized battery of 11 cognitive tasks. The study was run double-blind and the order of treatment conditions over successive visits was counterbalanced between subjects. Scopolamine produced marked and significant decrements on all major aspects of performance from the battery. The drug lowered the efficiency of the detection and processing of information in tests of visual vigilance, rapid information processing, choice reaction, letter cancellation and logical reasoning. These effects were accompanied by a lowering of critical flicker-fusion frequency and subjective alertness. Memory was also impaired on tests of immediate recall, delayed recall, recognition and memory scanning. These findings confirm and extend previous work, demonstrating that scopolamine impairs the selection and evaluation of environmental information, as well as reducing the likelihood of information being subsequently recalled or recognized. Whether the former effects contribute to the latter is not known, but this must be considered a possibility. This potential role of processing deficits in memory loss associated with cholinergic blockade is briefly considered in relation to the cholinergic hypothesis of geriatric memory loss.
The purpose of the study was to examine the influence of oxygen-breathing on maximal oxygen uptake (\(\dot V\)O2max) and submaximal endurance performance. Six young women and five men rode a cycle-ergometer while breathing compressed air (normoxia, NOX) or a 55% O2 in N2 mixture (hyperoxia, HOX). The\(\dot V\)O2max increased significantly by 12% (P<0.01) with HOX in the women but not in the men (+4%; nonsignificant). Maximal heart rate was also increased with HOX in the women but not in the men. Endurance time during work to -exhaustion at 80% of normoxic\(\dot V\)O2max was 41% longer in HOX than in NOX (P<0.025) with no significant difference between the men and the women. The variation among individuals was large. The oxygen uptake and respiratory quotient were not different in the two endurance tests, but pulmonary ventilation (\(\dot V\) E) and blood lactate concentration were lower in HOX than in NOX, especially during the latter part of the task. Plasma base deficit (BDpi) increased initially by 3.5 mmol · l−1 during HOX and then stabilized. In NOX, a continuous increase was seen and the change was more than twice as large. Relative to BDpl,\(\dot V\) E was higher in HOX than in NOX indicating a more efficient ventilatory compensation of the metabolic acidosis. The reduced ventilatory demand and lower metabolic acidosis in HOX in combination with lower relative exercise intensity may have contributed to the longer time to exhaustion. However, the pattern of individual variation suggested that other mechanisms were also involved.
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With the use of advanced equipment, respiratory measures can unobtrusively and reliably be assessed in a variety of psychophysiological research settings. New computerized analysis techniques can break down respiration into a number of components that provide valid estimates of variations in respiratory control mechanisms in the brain stem. Thus analysed, respiratory responses may vary in at least two dimensions: (A) with regard to drive and timing aspects, and (B) with regard to the metabolic appropriateness of the respiratory response. Assessment of respiratory responses may be relevant for a broad variety of research areas, including studies of the physiological effects of mental load and stress, investigations of physiological correlates of emotions and affect, and research linking physiological responses to subjective distress and psychosomatic disorders.
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Sustained exposure to high terrestrial altitudes is associated with cognitive decrement, mood changes, and acute mountain sickness (AMS). Such impairment in aviators could be a safety hazard. Thirteen male soldiers, ages 19-24, ascended in 10 min from sea level to 4,300 m (simulated), and remained there 2.5 d. Four times per day, subjects completed a test battery consisting of nine cognitive tests, a mood scale, and an AMS questionnaire. During one test session per day, subjects breathed 35% oxygen instead of ambient air. Analysis revealed transient deficits on altitude day 1 for three cognitive tasks. Most tasks displayed a persistent training effect. Sick subjects' moods were more negative and their performance improvement less. On altitude day 1, oxygen administration improved performance on two cognitive tests and one mood subscale. Following rapid ascent to 4,300 m, performance is most affected during the first 8 h. Individuals affected by AMS tend to improve more slowly in performance and have more negative moods than those who feel well.
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To evaluate counterregulatory hormone secretion and neuropsychologic function during hypoglycemia in two groups of patients with insulin-dependent diabetes mellitus: those with good and those with poor glycemic control. Cross-sectional physiologic and neuropsychologic evaluation. Clinical research unit of a referral-based diabetes clinic. Eight patients with well controlled diabetes (glycosylated hemoglobin [HgbA1], 8.0% +/- 0.2%), nine patients with poorly controlled diabetes (HgbA1, 11.8% +/- 0.4%), and ten healthy persons. The insulin clamp technique was used to produce a stepwise decline in plasma glucose from 5.0 to 2.2 mmol/L over 3 hours. Tests of attention, memory, visual-spatial skills, visual-motor skills, and global cognition; a symptom survey; and counterregulatory hormone measurements were done at glucose decrements of 0.6 mmol/L. Patients with well controlled diabetes did not differ statistically from those with poorly controlled diabetes regarding the median glucose threshold for dysfunction in visual-spatial skills, visual-motor skills, or global cognition. In contrast, glycemic thresholds for an increase in adrenergic symptoms and release of epinephrine, norepinephrine, cortisol, and growth hormone were lower in patients with well controlled diabetes than in those with poorly controlled diabetes (P less than 0.05 to 0.005). Despite alterations in the glucose levels at which adrenergic symptoms of hypoglycemia occur and counterregulation begins, there is no statistically detectable change in the glucose threshold at which cognitive deterioration occurs in diabetic persons with strict glycemic control. This dissociation of neuropsychologic function and counterregulatory hormone secretion suggests that diabetic patients with good glycemic control are at increased risk for developing cognitive impairment before the onset of adrenergic symptoms during hypoglycemia.
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This review presents evidence that some cognition enhancing drugs produce their beneficial effects on learning and memory by increasing the availability of glucose for uptake and utilization into the brain. The hypothesis further suggests that many cognition enhancing drugs act through a peripheral mechanism rather than directly on the brain. The general hypothesis is supported by four independent and converging pieces of evidence: 1) Some cognition enhancing drugs may not cross the blood-brain barrier, but can still facilitate memory; 2) Some cognition enhancing drugs are effective only when injected peripherally, but not when injected directly into the brain; 3) Many cognition enhancing drugs are not effective after adrenalectomy; 4) Cognitive function is correlated with glucose regulation in aged animals and humans. These four lines of research have implications for the role of glucose in the action of specific cognitive enhancers.
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In an attempt to find out whether decreased blood sugar level is associated with impaired cognitive function, adverse emotional changes, or somatic symptoms, 35 subjects who suspected that they had hypoglycemia were given 5-hr glucose tolerance tests (GTTs). Nine blood samples were taken during the GTT, and the subject's mood, Serial Sevens Test (SST) performance, and somatic symptom reports were recorded on each occasion of sampling. The subjects reported significantly more negative affect and somatic symptoms after glucose nadir than before nadir. SST performance deteriorated at glucose nadir. These effects were more pronounced for subjects with high hypoglycemic index scores than for subjects with low index scores. The impairment in SST performance was greater for subjects who showed rapid decreases in blood sugar than for subjects who showed slow decreases. Dividing subjects by high and low nadirs did not reveal any differences in symptomatology.
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Psychomotor performance was assessed in 20 subjects on each of 2 mountaineering expeditions. During the first, which reached 5,008 m, simple reaction time and alertness were measured, on the second to 4,790 m these were replaced by a three-choice reaction time test. In both, mean reaction times increased significantly at altitude in subjects with marked symptoms of Acute Mountain Sickness (AMS), whereas the alertness tests showed no effects. Reaction times were not affected by other environmental factors but adverse conditions increased the number of errors. The increase in reaction time may be ascribed either to the lethargy associated with AMS or alternatively may have been a direct effect of hypoxia. The latter explanation is favoured because of reports by other workers of an increase in reaction time with altitude in the absence of AMS.
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Heart rate, plus various metabolic and ventilatory indices, were monitored while 20 young male subjects were exposed to a video game and a stressful mental arithmetic task. Measurements were also made while subjects undertook graded isotonic exercise. All measures changed as a function of psychological challenge, and during exercise physiological activity increased as an orderly function of workload. For each subject, heart rate was plotted against oxygen consumption over the various exercise loads. For the majority of subjects the analogous data points for the video game and mental arithmetic lay reliably above the exercise heart rate-oxygen consumption regression lines. When these regression lines were used to predict heart rate values during psychological challenge, the predicted values were significantly less than the values actually recorded for both tasks; although the discrepancy between predicted and actual values was on average greater with mental arithmetic, the difference was not statistically reliable. Pre-stressor baseline conditions were also associated with heart rate levels greater than predicted, albeit to a lesser extent. Finally, while both stressors produced heart rate adjustments additional to expectancies, inter-task consistency was low.
Article
Hypoxia is commonly invoked to explain alterations in mental function, particularly in patients with cardiac pulmonary failure. The effects of acute graded hypoxia or higher integrative functions are well documented experimentally in man. Hypoxia in experimental animal models demonstrates that the pathophysiology is complex. In mild to moderate hypoxia, in contrast to severe hypoxia and to ischemia, the supply of energy for the brain is not impaired; cerebral levels of adenosine triphosphate (ATP) and adenylate energy charge are normal. In contrast, the turnover of several neurotransmitters is altered by mild hypoxia. For example, acetylcholine synthesis is reduced proportionally to the reduction in carbohydrate oxidation. This relationship holds in vitro and with several in vivo models of hypoxia. Pharmacologic and physiologic studies in man and experimental animals are consistent with acetylcholine having an important role in mediating the cerebral effects of mild hypoxia. These observations raise the possibility that treatments directed to cholinergic or other central neurotransmitter systems may benefit patients with cerebral syndromes secondary to chronic hypoxia.
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This chapter discusses the positron emission tomographic studies of local cerebral glucose metabolism in humans in physiological and pathophysiological conditions. Glucose utilization is stoichiometrically related to oxygen consumption in the aerobic state, except in a few situations such as starvation and insulin hypoglycemia, and provides a measure of energy metabolism in the anaerobic state as well. The ability to detect alterations in local cerebral metabolism in man has become a valuable tool in advancing our understanding of disorders affecting the brain, many of which are focal in nature. In order to determine the regional metabolic rate for glucose, one must measure, the distribution of the ¹⁸F activity in the brain, the time course of arterial plasma ‘¹⁸F’fluorodeoxyglucose (‘¹⁸F’FDG) and glucose concentrations, and know the values of the rate constants and lumped constant for FDG in humans. The three-dimensional distribution of ¹⁸F activity in the brain is determined with a positron emission tomographic scanner. Such an instrument consists of an array of scintillation detectors positioned around the subject's head. The detectors are mounted on a gantry capable of rectilinear and/or rotatory motion. From the measured data, transverse sections through the brain are calculated using a filtered, back-projection reconstruction technique.
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These studies demonstrated increasing glucose metabolic rates in the human primary (PVC) and associative (AVC) visual cortex as the complexity of visual scenes increased. The metabolic response of the AVC increased more rapidly with scene complexity than that of the PVC, indicating the greater involvement of the higher order AVC for complex visual interpretations. Increases in local metabolic activity by as much as a factor of 2 above that of control subjects with eyes closed indicate the wide range and metabolic reserve of the visual cortex.
Article
The present study was designed to search for concomitant age-related changes in memory subsystems, defined according to current structural theories, and resting oxygen consumption in selected brain regions. We have investigated a sample of subjects between 20 and 68 years of age and strictly screened for their good health. We applied in the same subjects a battery of neuropsychological tests selected to investigate several memory subsystems, and high-resolution positron imaging with stereotaxic localization to study a purposely limited number of cerebral structures, selected on a priori hypotheses to match the different memory subsystems. Our results showed significant age-related changes in performance on some tests, consistent with the literature, including an increase in semantic memory and a decrease in both working memory (central executive system) and verbal episodic and explicit memory. There was also an age-related linear decrease in global brain oxygen consumption which regionally reached statistical significance for the neocortical areas and the left thalamus. There was a limited number of significant, age-independent correlations between the raw psychometric test scores and resting regional oxidative metabolism. Consistent with our present understanding of the functional anatomy of memory, the Associate Learning scores (verbal episodic and explicit memory) were positively correlated with left hippocampal and thalamic metabolism. The positive relationships found between right hippocampal metabolism and performance in the Associate Learning and the Brown-Peterson tests were less expected but would be consistent with findings from recent PET activation studies. The results from this investigation are discussed in the light of current knowledge concerning the neuropsychology and the neurobiology of both aging and memory.
Article
The relationship between performance on a dichotic listening task and blood glucose levels was examined. It was predicted that, if the ability of blood glucose to supply the brain with its basic fuel limits performance under conditions of cognitive demand, in a dichotic listening task information directed to the left hemisphere would be particularly susceptible to the level of blood glucose. Via headphones subjects heard lists of words directed to both ears, although randomly they were asked to attend to those directed to one ear. Those receiving a glucose drink recalled more of a list of words directed to the right ear and hence the left hemisphere. Subjects with low baseline blood glucose levels recalled more from the attended ear, and those with high baseline blood glucose more from the unattended ear. In those who received a glucose drink, a fail in blood glucose during the dichotic task was associated with a right ear superiority. The pattern of findings can be explained by the assumptions that under conditions of cognitive demand the supply of glucose to the brain limits performance and that there are individual differences in the ability to efficiently take glucose from the blood stream into the brain.
Article
It has been suggested that cerebral adaptation may occur in response to short-term hypoglycemia. This was examined in the present study by measuring serial changes in cognitive function and symptoms after 60 min of continuous hypoglycemia. Hypoglycemia was induced with a hyperinsulinemic glucose clamp on two separate occasions in 24 non-diabetic human subjects. Cognitive function was assessed using the following cognitive test battery: Paced Auditory Serial Addition Test (PASAT), Rapid Visual Information Processing (RVIP), Trail-Making B (TMB), Digit Symbol Substitution Test (DSST) and Four Choice Reaction Time (CRT). In condition A the blood glucose was maintained at 4.5 mmol/l throughout. On two separate occasions (condition B and condition C) the blood glucose was stabilised at 4.5 mmol/l for 30 min, lowered to 2.5 mmol/l for 60 min and restored to 4.5 mmol/l for 30 min. In each condition the cognitive test battery was performed immediately after stabilisation of blood glucose at 4.5 mmol/l and the subsequent battery was repeated at different time intervals: condition A--after a further 40 min of euglycemia; condition B--after 5 min of hypoglycemia; condition C--after 40 min of hypoglycemia. Acute hypoglycemia induced a significant deterioration in cognitive function which was manifest in all tests except TMB (P < 0.05), but performance ability did not differ between conditions B and C. Symptom scores, assessed by a scaled questionnaire, increased significantly during hypoglycemia (P < 0.001) but no differences were detected between the scores at 30 min and 60 min.(ABSTRACT TRUNCATED AT 250 WORDS)
Article
Functional neuroimaging has become a powerful tool for investigating the neurobiological foundations of cognition. An overview is presented of the two major strategies by which such data are currently analyzed. One strategy compares the pattern of activity between two (or more) tasks, looking for those brain areas that show significant changes. The second investigates the functional relationships between regional activities in an attempt to determine the systems-level neural networks mediating the tasks. Object and spatial visual processing tasks are used to illustrate each of these strategies.
Article
As it has been suggested that blood glucose might play a role in the action of some cognitive enhancing drugs, the influence of glucose containing drinks on human memory was examined. In a double-blind study the influence was examined of a drink containing 50 g glucose, or a placebo, on the ability to recall a word list. There was a significant correlation between blood glucose values and the number of words recalled. Those whose blood glucose levels were increasing remembered significantly more words than those whose blood glucose levels were falling. No relationship was found between blood glucose and performance on a test of spatial memory. In a second study blood glucose levels were raised for 2 h by taking a series of glucose-containing drinks. The number of words recalled from a word list correlated significantly with blood glucose levels but not with recall of a Wechsler story. The glucose-induced improvement in memory did not occur only in those whose blood glucose levels were initially low; rather it occurred irrespective of initial blood glucose level.
Article
The positive action of nootropics on the memory has up to now primarily been discussed in the context of effects on energy metabolism and cholinergic or glutaminergic neurotransmission. Recent findings have shown that the memory-enhancing effect is steroid-sensitive. Since corticosteroids are potent modulators of gene transcription, it appears possible that the nootropics may exert a modulatory action on protein synthesis. This assumption is supported on the one hand by the fact that the nootropics improve the memory even if they are administered several hours after the learning trial, and on the other hand by the observation that their memory-enhancing effect does not become detectable until 16-24 hours after the treatment and learning trial. Provided the memory-enhancing effect in animal experiments and the therapeutic effect in patients come about by way of the same mode of action, the fact that high levels of corticosteroids suppress the effects of the nootropics could also have clinical implications: in the light of the observation that the majority of Alzheimer patients have elevated steroid levels it could explain why there is always only a small proportion of patients in clinical trials that respond to treatment with nootropics.
Article
There is evidence from animal studies that increased blood glucose levels are associated with improved memory and attention. Although previous studies have found human memory to be facilitated by the administration of glucose, attentional measures have been largely ignored. Therefore the impact of a glucose drink, or a placebo, on the Rapid Information Processing Task and the Stroop Task was examined. The reaction times of those taking the Rapid Information Processing Task were faster both during the baseline period and after a glucose drink if the blood glucose values were high. With the Stroop task the ability to perform the most cognitively demanding sub-test was selectively enhanced if blood glucose values were increasing prior to starting the test. The ability to recall words from a word list was greater if a glucose drink had been consumed, although primary and recency were not differentially influenced. The possibility is discussed that higher levels of brain glucose are associated with better memory and attention.
Article
Normobaric hyperoxia decreases heart rate (HR) in humans and animals. This study explored the mechanisms of hyperoxic bradycardia by examining its response time, autonomic neural mediation, and reversibility in conscious dogs. Five trained mongrel dogs breathed from a mask as the inspired gas was alternated between air and O2 for multiple cycles, and continuous time series records of HR and oxyhemoglobin saturation were recorded on a digital computer and analyzed by the technique of ensemble averaging. Hyperoxia decreased HR by 9% (P < 0.001), but only gradually, requiring 5 min to reach steady state. This delay was much longer than the time required for hyperoxic respiratory depression (10-20 s), a response known to be mediated by chemoreceptor reflexes. The bradycardia was sustained for > or = 30 min. On return to normoxia, HR gradually returned toward, but failed to reach, the baseline HR, suggesting incomplete reversibility of the response. However, in control experiments without hyperoxic challenge, HR showed a slow continuous downward trend that was sufficient to account for the apparent incomplete reversibility of hyperoxic bradycardia. Hyperoxic bradycardia was unaffected by beta-adrenergic blockade but was completely prevented by muscarinic cholinergic blockade. We conclude that 1) hyperoxia-induced bradycardia in conscious dogs is mediated by efferents of the vagus nerve; 2) its afferent pathway remains unknown, but its long response time suggests mechanisms other than chemoreceptor reflexes or other known neural reflexes; and 3) it is completely reversible.
Article
Up to now, the memory-enhancing effect of the nootropics has chiefly been investigated in the context of effects on energy metabolism and on cholinergic and glutamatergic neurotransmission. Recent studies have also shown that the effect on memory is steroid-sensitive. The present review article summarizes the available results and discusses them in the context of a new hypothesis on the mechanism of action and with respect to clinical implications.
Article
24 participants (12 female) performed a continuous memory task during which metabolic, cardiorespiratory, performance, and subjective mental workload measures were taken. Task difficulty was varied using two manipulations in a within-subjects factorial design: memory load (one or three items) and temporal demand (interstimulus intervals of 2, 3, or 4 s). Males and females differed in initial metabolic rate, but did not differ in their response to the task. Memory load affected all measures, while temporal demand affected only respiration rate, performance, and subjective mental workload. Metabolic, Respiratory, Cardiovascular, and Subjective/Performance components were identified in a principal components analysis (PCA), and the Respiratory and Subjective/Performance components were affected by the task manipulations. When performance quality was examined, the Metabolic component revealed that poor performers had greater energy expenditure during the task than good performers, and the Cardiovascular component revealed that good and poor performers differed in their response to memory load and temporal demand. Cardiac and metabolic changes during mental work were not a function of overall mental effort, but were specific to the effort due to memory load and to the individual differences among participants in their ability to perform the task. However, respiration was sensitive to the mental effort associated with both memory load and temporal demand, but was not sensitive to individual differences.