Rostral prefrontal cortex (approximating Brodmann area 10) has been shown repeatedly to have a role in the maintenance and realization of delayed intentions that are triggered by event cues (i.e., event-based prospective memory). The cerebral organization of the processes associated with the use of time cues (time-based prospective memory) has however received less attention. In two positron emission tomography (PET) studies we therefore examined brain activity associated with time- and event-based prospective memory tasks. In the time-based condition of the first study, young healthy volunteers were asked to make a prospective response based on their self-estimation of the passage of time while engaged in an attention-demanding ongoing activity. In the time-based condition of the second study, participants had a clock available in the ongoing task display and did not need to estimate the time for the prospective response. In the event-based condition of both studies, participants were asked to make a prospective response when prospective cues were presented in ongoing trials. Both studies showed activation differences in rostral prefrontal cortex according to whether the task was time- or event-based. In study one, an area of left superior frontal gyrus was more active in the time-based condition. In study two, three rostral prefrontal regions were more active in the time-based condition: right superior frontal gyrus, anterior medial frontal lobe and anterior cingulate gyrus. A region in left superior frontal gyrus, different from the area found in the first study, was more active in the event-based condition. These results indicate involvement of multiple brain regions of rostral prefrontal cortex in time- and event-based prospective memory. The results are interpreted as reflecting the differing processing demands made by event- or time-based prospective memory tasks, and the differing demands of time-based tasks according to whether a clock is present as an aid.
"memory (right BA7: Ranganath et al., 2003) and perception of personal space (right BA7: Lloyd and Morrison, 2008), deductive reasoning (left BA6: Reverberi et al., 2007), prospective memory (left BA10: Okuda et al., 2007), attribution of intentions to others (right BA9: Brunet et al., 2000), true and false memory recognition (left BA37: Slotnick and Schacter, 2004). Our results suggest that the disturbance of these particular functions in schizophrenia is represented in the brain with two distinct electrophysiological mechanisms: increased coupled inhibition (increased delta connectivity) and decreased coupled facilitation (decreased alpha-1 activity). "
[Show abstract][Hide abstract] ABSTRACT: Functional dissociation between brain processes is widely hypothesized to account for aberrations of thought and emotions in schizophrenic patients. The typically small groups of analyzed schizophrenic patients yielded different neurophysiological findings, probably because small patient groups are likely to comprise different schizophrenia subtypes. We analyzed multichannel eyes-closed resting EEG from three small groups of acutely ill, first episode productive schizophrenic patients before start of medication (from three centers: Bern N = 9; Osaka N = 9; Berlin N = 12) and their controls. Low resolution brain electromagnetic tomography (LORETA) was used to compute intracortical source model-based lagged functional connectivity not biased by volume conduction effects between 19 cortical regions of interest (ROIs). The connectivities were compared between controls and patients of each group. Conjunction analysis determined six aberrant cortical functional connectivities that were the same in the three patient groups. Four of these six concerned the facilitating EEG alpha-1 frequency activity; they were decreased in the patients. Another two of these six connectivities concerned the inhibiting EEG delta frequency activity; they were increased in the patients. The principal orientation of the six aberrant cortical functional connectivities was sagittal; five of them involved both hemispheres. In sum, activity in the posterior brain areas of preprocessing functions and the anterior brain areas of evaluation and behavior control functions were compromised by either decreased coupled activation or increased coupled inhibition, common across schizophrenia subtypes in the three patient groups. These results of the analyzed three independent groups of schizophrenics support the concept of functional dissociation.
Frontiers in Human Neuroscience 08/2014; 8:635. DOI:10.3389/fnhum.2014.00635 · 2.99 Impact Factor
"Prefrontal lobe pathology in these patients has also been confirmed in fMRI (Dumontheil et al., 2008) and post-mortem studies (Vogeley et al., 2003). Neuroimaging studies also point to the primary role played by the prefrontal lobes, particularly Brodmann area 10, in PM performance (Okuda et al., 2007; Burgess et al., 2008; Reynolds et al., 2009), although involvement of the parietal lobes has also been implicated (Burgess et al., 2011). PM deficits have been repeatedly found in schizophrenia (Shum et al., 2004; Wang et al., 2009; Au et al., 2012; Zhou et al., 2012; Raskin et al., 2013). "
[Show abstract][Hide abstract] ABSTRACT: Schizophrenia patients are known to have prospective memory (PM) deficits. There is no robust evidence showing that PM deficits have a major impact on community living skills in schizophrenia. The aim of this study was to examine the association between PM and community living skills in schizophrenia. Forty-four individuals with schizophrenia formed the study sample. Participants׳ psychopathology, prospective and retrospective memory, level of intelligence, and community living skills were measured with standardized instruments. In bivariate analyses, community living skills overall but not self-care correlated with PM total and subscales scores. In multivariate analyses, event-based PM was more predictive than time-based PM of the level of community living skills. In conclusion, PM has a significant impact on community living skills in schizophrenia and attention should be paid to this type of memory disturbance in rehabilitation of schizophrenia.
Psychiatry Research 05/2014; 219(1). DOI:10.1016/j.psychres.2014.04.055 · 2.47 Impact Factor
"Accordingly, lesions in the rostral PFC manifest as tardiness and disorganization, regardless of intellect and social skills
[26-28]. Imaging studies of BA10 observed increased recruitment of the rostral parts of BA10 in multi-tasking conditions compared to a control task
[27,29], consistent with the present and previous research in young adults
[13,14]. Thus, the current finding of PFC activation during multitasking confirms the relationship between dual tasking and prefrontal lobe function, while also extending it, as detailed further below. "
[Show abstract][Hide abstract] ABSTRACT: Background
Accumulating evidence suggests that gait is influenced by higher order cognitive and cortical control mechanisms. Recently, several studies used functional near infrared spectroscopy (fNIRS) to examine brain activity during walking, demonstrating increased oxygenated hemoglobin (HbO2) levels in the frontal cortex during walking while subjects completed a verbal cognitive task. It is, however, still unclear whether this increase in activation was related to verbalization, if the response was specific to gait, or if it would also be observed during standing, a different motor control task. The aim of this study was to investigate whether an increase in frontal activation is specific to dual tasking during walking.
Twenty-three healthy young adults (mean 30.9 ± 3.7 yrs, 13 females) were assessed using an electronic walkway. Frontal brain activation was assessed using an fNIRS system consisting of two probes placed on the forehead of the subjects. Assessments included: walking in a self-selected speed; walking while counting forward; walking while serially subtracting 7s (Walking+S7); and standing while serially subtracting 7s (Standing+S7). Data was collected from 5 walks of 30 meters in each condition. Twenty seconds of quiet standing before each walk served as baseline frontal lobe activity. Repeated Measures Analysis of Variance (RM ANOVA) tested for differences between the conditions.
Significant differences were observed in HbO2 levels between all conditions (p = 0.007). HbO2 levels appeared to be graded; walking alone demonstrated the lowest levels of HbO2 followed by walking+counting condition (p = 0.03) followed by Walking+S7 condition significantly increased compared to the two other walking conditions (p < 0.01). No significant differences in HbO2 levels were observed between usual walking and the standing condition (p = 0.38) or between standing with or without serial subtraction (p = 0.76).
This study provides direct evidence that dual tasking during walking is associated with frontal brain activation in healthy young adults. The observed changes are apparently not a response to the verbalization of words and are related to the cognitive load during gait.
Journal of NeuroEngineering and Rehabilitation 05/2014; 11(1):85. DOI:10.1186/1743-0003-11-85 · 2.74 Impact Factor
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