Men perform comparably to women in a perspective taking task after administration of intranasal oxytocin but not after placebo

Oxytocin (OT) is thought to play an important role in human interpersonal information processing and behavior. By inference, OT should facilitate empathic responding, i.e. the ability to feel for others and to take their perspective. In two independent double-blind, placebo-controlled between-subjects studies, we assessed the effect of intranasally administered OT on affective empathy and perspective taking, whilst also examining potential sex differences (e.g., women being more empathic than men). In study 1, we provided 96 participants (48 men) with an empathy scenario and recorded self reports of empathic reactions to the scenario, while in study 2, a sample of 120 individuals (60 men) performed a computerized implicit perspective taking task. Whilst results from Study 1 showed no influence of OT on affective empathy, we found in Study 2 that OT exerted an effect on perspective taking ability in men. More specifically, men responded faster than women in the placebo group but they responded as slowly as women in the OT group. We conjecture that men in the OT group adopted a social perspective taking strategy, such as did women in both groups, but not men in the placebo group. On the basis of results across both studies, we suggest that self-report measures (such as used in Study 1) might be less sensitive to OT effects than more implicit measures of empathy such as that used in Study 2. If these assumptions are confirmed, one could infer that OT effects on empathic responses are more pronounced in men than women, and that any such effect is best studied using more implicit measures of empathy rather than explicit self-report measures.

Attribution d'intentions hostiles et intentions comportementales agressives dans un contexte intergroupes

We conducted two experiments to demonstrate the relevance of group membership (in-group vs. out-group) in the processing of conflictual social interactions as described by Dodge (1980; Dodge, Pettit, Mcclaskey, & Brown, 1986). In the first study, we highlighted the impact of group membership on the attribution of hostile intents and on reactions to a provocation. In the second study we found that the impact of group membership on aggressive reaction intents is moderated by the status of people in the interaction, and that this effect is partially mediated by attribution of hostile intents. We conclude by stressing the necessity to integrate intergroup dynamics in the social information processing model elaborated by Dodge.

Developing and Applying Generative Market Intelligence within Multinational Companies

Tutkielman tarkoitus on kehittää monikansallisille yrityksille tuottavan markkinaälyn malli, jonka avulla yritykset pystyvät käsittelemään muuttuvasta ja globalisoituvasta markkinaympäristöstä aiheutuvaa epävarmuutta. Malli koostuu pääosin kolmesta käsitteestä: markkinainformaation prosessoinnista, markkinasuuntautuneisuudesta ja organisationaalisesta oppimisesta. Tutkimuksessa osoitetaan, kuinka näiden samanaikainen soveltaminen johtaa synergiaetuihin. Lähdeaineistona käytettiin alan kirjallisuutta. Lisäksi haastateltiin neljää johtajaa monikansallisista yrityksistä. Käytännössä markkinaälyn soveltamisen haasteet liittyvät lähinnä markkinainformaation prosessoinnin asenteellisiin ja psykologisiin aspekteihin. Ihmisten tulisi ymmärtää, että koko yritys hyötyy heidän halukkuudestaan tiedon tuottamiseen ja jakamiseen. Lisäksi tietoa itsessään voimavarana tulisi kunnioittaa

Maturation and Functional Integration of New Granule Cells into the Adult Hippocampus.

The adult hippocampus generates functional dentate granule cells (GCs) that release glutamate onto target cells in the hilus and cornus ammonis (CA)3 region, and receive glutamatergic and γ-aminobutyric acid (GABA)ergic inputs that tightly control their spiking activity. The slow and sequential development of their excitatory and inhibitory inputs makes them particularly relevant for information processing. Although they are still immature, new neurons are recruited by afferent activity and display increased excitability, enhanced activity-dependent plasticity of their input and output connections, and a high rate of synaptogenesis. Once fully mature, new GCs show all the hallmarks of neurons generated during development. In this review, we focus on how developing neurons remodel the adult dentate gyrus and discuss key aspects that illustrate the potential of neurogenesis as a mechanism for circuit plasticity and function.

Effectiveness of instructional strategies based on schema theory on attention deficit disorder children

A review of the literature reveals that there are a number of children in the educational system who are characterized by Attention Deficit Disorder. Further review of the literature reveals that there are information processing programs which have had some success in increasing the learning of these children. Currently, an information processing program which is based on schema theory is being implemented in Lincoln County. Since schema theory based programs build structural, conditional, factual, and procedural schemata which assist the learner in attending to salient factors, learning should be increased. Thirty-four children were selected from a random sampling of Grade Seven classes in Lincoln County. Seventeen of these children were identified by the researcher and classroom teacher as being characterized by Attention Deficit Disorder. From the remaining population, 17 children who were not characterized by Attention Deficit Disorder were randomly selected. The data collected were compared using independent t-tests, paired t-tests, and correlation analysis. Significant differences were found in all cases. The Non-Attention Deficit Disorder children scored significantly higher on all the tests but the Attention Defici t Disorder children had a significantly higher ratio of gain between the pretests and posttests.

The efficacy of cognitive retraining of attentional deficits for a client who has schizophrenia

The purpose of this study was to assess the efficacy of the Process Specific Approach to cognitive rehabilitation for a client with schizophrenia who has attentional deficits. The study was a single case experimental design which followed a variation of the multiple baseline approach. Prior to training of the attentional deficit, multiple baseline assessments were completed. These included an ov:erview of the sUbject's information processing ability, random measures of attention and a genera.l level of functioning in living, learning and working environments. During the re-training, attention tests were administered at the completion of each attention component. A general functional evaluation through interviews and a measure of information processing ability were. completed after the re-training was concluded. The results of the study demonstrate a significant i'mprovement in attention and memory measures. Qualitative data indicate si·gni.ficant others observed improvements in performance in r livi'ng, learning and working environments. The results suggest this approach to cognitive rehabilitation was effective with this subject and further research to establish generalizability is recommended.

Verbal ability, previous practice and load on short-term memory as determiners of differences in a complex learning task: an experimental study

Traditional psychometric theory and practice classify people according to broad ability dimensions but do not examine how these mental processes occur. Hunt and Lansman (1975) proposed a 'distributed memory' model of cognitive processes with emphasis on how to describe individual differences based on the assumption that each individual possesses the same components. It is in the quality of these components ~hat individual differences arise. Carroll (1974) expands Hunt's model to include a production system (after Newell and Simon, 1973) and a response system. He developed a framework of factor analytic (FA) factors for : the purpose of describing how individual differences may arise from them. This scheme is to be used in the analysis of psychometric tes ts . Recent advances in the field of information processing are examined and include. 1) Hunt's development of differences between subjects designated as high or low verbal , 2) Miller's pursuit of the magic number seven, plus or minus two, 3) Ferguson's examination of transfer and abilities and, 4) Brown's discoveries concerning strategy teaching and retardates . In order to examine possible sources of individual differences arising from cognitive tasks, traditional psychometric tests were searched for a suitable perceptual task which could be varied slightly and administered to gauge learning effects produced by controlling independent variables. It also had to be suitable for analysis using Carroll's f ramework . The Coding Task (a symbol substitution test) found i n the Performance Scale of the WISe was chosen. Two experiments were devised to test the following hypotheses. 1) High verbals should be able to complete significantly more items on the Symbol Substitution Task than low verbals (Hunt, Lansman, 1975). 2) Having previous practice on a task, where strategies involved in the task may be identified, increases the amount of output on a similar task (Carroll, 1974). J) There should be a sUbstantial decrease in the amount of output as the load on STM is increased (Miller, 1956) . 4) Repeated measures should produce an increase in output over trials and where individual differences in previously acquired abilities are involved, these should differentiate individuals over trials (Ferguson, 1956). S) Teaching slow learners a rehearsal strategy would improve their learning such that their learning would resemble that of normals on the ,:same task. (Brown, 1974). In the first experiment 60 subjects were d.ivided·into high and low verbal, further divided randomly into a practice group and nonpractice group. Five subjects in each group were assigned randomly to work on a five, seven and nine digit code throughout the experiment. The practice group was given three trials of two minutes each on the practice code (designed to eliminate transfer effects due to symbol similarity) and then three trials of two minutes each on the actual SST task . The nonpractice group was given three trials of two minutes each on the same actual SST task . Results were analyzed using a four-way analysis of variance . In the second experiment 18 slow learners were divided randomly into two groups. one group receiving a planned strategy practioe, the other receiving random practice. Both groups worked on the actual code to be used later in the actual task. Within each group subjects were randomly assigned to work on a five, seven or nine digit code throughout. Both practice and actual tests consisted on three trials of two minutes each. Results were analyzed using a three-way analysis of variance . It was found in t he first experiment that 1) high or low verbal ability by itself did not produce significantly different results. However, when in interaction with the other independent variables, a difference in performance was noted . 2) The previous practice variable was significant over all segments of the experiment. Those who received previo.us practice were able to score significantly higher than those without it. J) Increasing the size of the load on STM severely restricts performance. 4) The effect of repeated trials proved to be beneficial. Generally, gains were made on each successive trial within each group. S) In the second experiment, slow learners who were allowed to practice randomly performed better on the actual task than subjeots who were taught the code by means of a planned strategy. Upon analysis using the Carroll scheme, individual differences were noted in the ability to develop strategies of storing, searching and retrieving items from STM, and in adopting necessary rehearsals for retention in STM. While these strategies may benef it some it was found that for others they may be harmful . Temporal aspects and perceptual speed were also found to be sources of variance within individuals . Generally it was found that the largest single factor i nfluencing learning on this task was the repeated measures . What e~ables gains to be made, varies with individuals . There are environmental factors, specific abilities, strategy development, previous learning, amount of load on STM , perceptual and temporal parameters which influence learning and these have serious implications for educational programs .

The role of daytime napping in sleepiness and cognitive function in 24-70 year olds /

Daytime napping improves well-being and performance for young adults. The benefits of napping in older adults should be investigated because they have fragmented nocturnal sleep, cognitive declines, and more opportunity to nap. In addition, experience with napping might influence the benefits of napping. Study 1 examined the role of experience with napping in young adults. Habitual (n = 23) and non-habitual nappers (n = 16) were randomly assigned to a 20-minute nap or a 20- minute reading condition. Both groups slept the same according to macro architecture. However, microarchitecture showed greater theta, alpha, and beta power during Stage 1, and greater delta, alpha, and sigma power during Stage 2 for habitual nappers, for the most part indicating better sleep. Both groups felt less sleepy after the nap. P2 latency, reflecting information processing, decreased after the nap for habitual nappers, and after the control condition for non-habitual nappers. In sum, both groups who slept felt better, but only the habitual nappers who napped gained a benefit in terms of information processing. Based on this outcome, experience with napping was investigated in Study 2. Study 2 examined the extent to which daytime napping enhanced cognition in older adults, especially frontal lobe function. Cognitive deficits in older adults may be due to sleep loss and age-related decline in brain functioning. Longer naps were expected to provide greater improvement, particularly for older adults, by reducing sleep pressure. Thirty-two adults, aged 24-70 years, participated in a repeated measures dose-response manipulation of sleep pressure. Twenty- and sixty-minute naps were compared to a no-nap condition in three age groups. Mood, subjective sleepiness, reaction time, working memory, 11 novelty detection, and waking electro physiological measures were taken before and after each condition. EEG was also recorded during each nap or rest condition. Napping reduced subjective sleepiness, improved working memory (serial addition / subtraction task), and improved attention (reduced P2 amplitude). Physiological sleepiness (i.e., waking theta power) increased following the control condition, and decreased after the longer nap. Increased beta power after the short nap, and seen with older adults overall, may have reflected increased mental effort. Older adults had longer latencies and smaller amplitudes for several event-related potential components, and higher beta and gamma power. Following the longer nap, gamma power decreased for older adults, but increased for young adults. Beta and gamma power may represent enhanced alertness or mental effort. In addition, Nl amplitude showed that benefits depend on the preceding nap length as well as age. Since the middle group had smaller Nl amplitudes following the short nap and rest condition, it is possible that they needed a longer nap to maintain alertness. Older adults did not show improvements to Nl amplitude following any condition; they may have needed a nap longer than 60 minutes to gain benefits to attention or early information processing. Sleep characteristics were not related to benefits of napping. Experience with napping was also investigated. Subjective data confirmed habitual nappers were happier to nap, while non-habitual nappers were happier to stay awake, reflecting self-identified napping habits. Non-habitual nappers were sleepier after a nap, and had faster brain activity (i.e., heightened vigilance) at sleep onset. These reasons may explain why non-habitual nappers choose not to nap.

Electrophysiological and behavioural correlates of facial identity and expression perception deficits following a closed head injury /

A large variety of social signals, such as facial expression and body language, are conveyed in everyday interactions and an accurate perception and interpretation of these social cues is necessary in order for reciprocal social interactions to take place successfully and efficiently. The present study was conducted to determine whether impairments in social functioning that are commonly observed following a closed head injury, could at least be partially attributable to disruption in the ability to appreciate social cues. More specifically, an attempt was made to determine whether face processing deficits following a closed head injury (CHI) coincide with changes in electrophysiological responsivity to the presentation of facial stimuli. A number of event-related potentials (ERPs) that have been linked specifically to various aspects of visual processing were examined. These included the N170, an index of structural encoding ability, the N400, an index of the ability to detect differences in serially presented stimuli, and the Late Positivity (LP), an index of the sensitivity to affective content in visually-presented stimuli. Electrophysiological responses were recorded while participants with and without a closed head injury were presented with pairs of faces delivered in a rapid sequence and asked to compare them on the basis of whether they matched with respect to identity or emotion. Other behavioural measures of identity and emotion recognition were also employed, along with a small battery of standard neuropsychological tests used to determine general levels of cognitive impairment. Participants in the CHI group were impaired in a number of cognitive domains that are commonly affected following a brain injury. These impairments included reduced efficiency in various aspects of encoding verbal information into memory, general slower rate of information processing, decreased sensitivity to smell, and greater difficulty in the regulation of emotion and a limited awareness of this impairment. Impairments in face and emotion processing were clearly evident in the CHI group. However, despite these impairments in face processing, there were no significant differences between groups in the electrophysiological components examined. The only exception was a trend indicating delayed N170 peak latencies in the CHI group (p = .09), which may reflect inefficient structural encoding processes. In addition, group differences were noted in the region of the N100, thought to reflect very early selective attention. It is possible, then, that facial expression and identity processing deficits following CHI are secondary to (or exacerbated by) an underlying disruption of very early attentional processes. Alternately the difficulty may arise in the later cognitive stages involved in the interpretation of the relevant visual information. However, the present data do not allow these alternatives to be distinguished. Nonetheless, it was clearly evident that individuals with CHI are more likely than controls to make face processing errors, particularly for the more difficult to discriminate negative emotions. Those working with individuals who have sustained a head injury should be alerted to this potential source of social monitoring difficulties which is often observed as part of the sequelae following a CHI.

Age-related changes in ERPs associated with context-based and response-based interference

Age-related differences in information processing have often been explained through deficits in older adults' ability to ignore irrelevant stimuli and suppress inappropriate responses through inhibitory control processes. Functional imaging work on young adults by Nelson and colleagues (2003) has indicated that inferior frontal and anterior cingulate cortex playa key role in resolving interference effects during a delay-to-match memory task. Specifically, inferior frontal cortex appeared to be recruited under conditions of context interference while the anterior cingulate was associated with interference resolution at the stage of response selection. Related work has shown that specific neural activities related to interference resolution are not preserved in older adults, supporting the notion of age-related declines in inhibitory control (Jonides et aI., 2000, West et aI., 2004b). In this study the time course and nature of these inhibition-related processes were investigated in young and old adults using high-density ERPs collected during a modified Sternberg task. Participants were presented with four target letters followed by a probe that either did or did not match one of the target letters held in working memory. Inhibitory processes were evoked by manipulating the nature of cognitive conflict in a particular trial. Conflict in working memory was elicited through the presentation of a probe letter in immediately previous target sets. Response-based conflict was produced by presenting a negative probe that had just been viewed as a positive probe on the previous trial. Younger adults displayed a larger orienting response (P3a and P3b) to positive probes relative to a non-target baseline. Older adults produced the orienting P3a and 3 P3b waveforms but their responses did not differentiate between target and non-target stimuli. This age-related change in response to targetness is discussed in terms of "early selection/late correction" models of cognitive ageing. Younger adults also showed a sensitivity in their N450 response to different levels of interference. Source analysis of the N450 responses to the conflict trials of younger adults indicated an initial dipole in inferior frontal cortex and a subsequent dipole in anterior cingulate cortex, suggesting that inferior prefrontal regions may recruit the anterior cingulate to exert cognitive control functions. Individual older adults did show some evidence of an N450 response to conflict; however, this response was attenuated by a co-occurring positive deflection in the N450 time window. It is suggested that this positivity may reflect a form of compensatory activity in older adults to adapt to their decline in inhibitory control.

Linking Ethical Leadership and Employees’ In-Role Performance: Exploring the Mediating Roles of Psychological Capital and Follower-Leader Relational Capital

This study investigates the mediating impact of psychological capital and follower-leader relational capital on the relationship between ethical leadership and in-role performance through the lenses of social exchange theory, social information processing theory, and psychological resources theory. Analysis of data collected from a sample of 171 employees and 24 supervisors from Pakistan reveals that ethical leadership has a positive effect on followers’ in-role job performance, yet this effect is fully explained through the role of psychological capital and partially through follower-leader relational capital. Significant implications of these findings for further research and practice are discussed.

Frontal Lobe Function and Performance Monitoring following Total Sleep Deprivation

Imaging studies have shown reduced frontal lobe resources following total sleep deprivation (TSD). The anterior cingulate cortex (ACC) in the frontal region plays a role in performance monitoring and cognitive control; both error detection and response inhibition are impaired following sleep loss. Event-related potentials (ERPs) are an electrophysiological tool used to index the brain's response to stimuli and information processing. In the Flanker task, the error-related negativity (ERN) and error positivity (Pe) ERPs are elicited after erroneous button presses. In a Go/NoGo task, NoGo-N2 and NoGo-P3 ERPs are elicited during high conflict stimulus processing. Research investigating the impact of sleep loss on ERPs during performance monitoring is equivocal, possibly due to task differences, sample size differences and varying degrees of sleep loss. Based on the effects of sleep loss on frontal function and prior research, it was expected that the sleep deprivation group would have lower accuracy, slower reaction time and impaired remediation on performance monitoring tasks, along with attenuated and delayed stimulus- and response-locked ERPs. In the current study, 49 young adults (24 male) were screened to be healthy good sleepers and then randomly assigned to a sleep deprived (n = 24) or rested control (n = 25) group. Participants slept in the laboratory on a baseline night, followed by a second night of sleep or wake. Flanker and Go/NoGo tasks were administered in a battery at 1O:30am (i.e., 27 hours awake for the sleep deprivation group) to measure performance monitoring. On the Flanker task, the sleep deprivation group was significantly slower than controls (p's <.05), but groups did not differ on accuracy. No group differences were observed in post-error slowing, but a trend was observed for less remedial accuracy in the sleep deprived group compared to controls (p = .09), suggesting impairment in the ability to take remedial action following TSD. Delayed P300s were observed in the sleep deprived group on congruent and incongruent Flanker trials combined (p = .001). On the Go/NoGo task, the hit rate (i.e., Go accuracy) was significantly lower in the sleep deprived group compared to controls (p <.001), but no differences were found on false alarm rates (i.e., NoGo Accuracy). For the sleep deprived group, the Go-P3 was significantly smaller (p = .045) and there was a trend for a smaller NoGo-N2 compared to controls (p = .08). The ERN amplitude was reduced in the TSD group compared to controls in both the Flanker and Go/NoGo tasks. Error rate was significantly correlated with the amplitude of response-locked ERNs in control (r = -.55, p=.005) and sleep deprived groups (r = -.46, p = .021); error rate was also correlated with Pe amplitude in controls (r = .46, p=.022) and a trend was found in the sleep deprived participants (r = .39, p =. 052). An exploratory analysis showed significantly larger Pe mean amplitudes (p = .025) in the sleep deprived group compared to controls for participants who made more than 40+ errors on the Flanker task. Altered stimulus processing as indexed by delayed P3 latency during the Flanker task and smaller amplitude Go-P3s during the Go/NoGo task indicate impairment in stimulus evaluation and / or context updating during frontal lobe tasks. ERN and NoGoN2 reductions in the sleep deprived group confirm impairments in the monitoring system. These data add to a body of evidence showing that the frontal brain region is particularly vulnerable to sleep loss. Understanding the neural basis of these deficits in performance monitoring abilities is particularly important for our increasingly sleep deprived society and for safety and productivity in situations like driving and sustained operations.

An Electrophysiological Investigation into the Role of Cognitive Control in the Attentional Blink

Accuracy at reporting a second-target (T2) is reduced if it is presented within approximately 500 ms of the first target (T1) – an attentional blink (AB). Early models explained the AB in terms of attentional limitations creating a processing bottleneck such that T2 processing would be impaired while T1 processing was ongoing. Theoretical models of the AB have more recently been expanded to include the role of cognitive control. In this dissertation I propose that cognitive control, defined as the optimization of information processing in order to achieve goals, is maladapted to the dual-task conditions of the AB task in that cognitive control optimizes the T1 goal, due to its temporal proximity, at the cost of T2. I start with the concept that the role of cognitive control is to serve goals, and that how goals are conceived of and the degree of motivation associated with those goals will determine whether cognitive control will create the condition that cause the AB. This leads to the hypothesis that electrophysiological measures of cognitive control and the degree of attentional investment resulting from cognitive control modulate the AB and explain individual differences in the AB. In a series of four studies feedback-related N2 amplitude, (reflecting individual differences in the strength of cognitive control), and event-related and resting alpha frequency oscillatory activity (reflecting degree of attentional investment), are used to explain both intra- and inter-individual variability in performance on the AB task. Results supported the hypothesis that stronger cognitive control and greater attentional investment are associated with larger AB magnitudes. Attentional investment, as measured by alpha frequency oscillations, and cognitive control, as measured by the feedback-related N2, did not relate to each other as hypothesized. It is proposed that instead of a measure of attentional investment alone, alpha frequency oscillatory activity actually reflects control over information processing over time, in other words the timing of attention. With this conceptualization, various aspects of cognitive control, either related to the management of goals (feedback-related N2) or the management of attention over time to meet goals, explain variability in the AB.

Plasticité présynaptique et gliale à long-terme en réponse à un changement chronique de l’activité synaptique,à la jonction neuromusculaire d’amphibien

La plasticité synaptique est une importante propriété du système nerveux, impliquée dans l’intégration de l’information. Cette plasticité a généralement été décrite par des changements aux niveaux pré et postsynaptiques. Notamment, l’efficacité présynaptique, soit la probabilité de libération de neurotransmetteurs associée au contenu quantique d’une synapse, peut être augmentée ou diminuée selon l’activité antérieure de la synapse. Malgré cette caractérisation, les mécanismes à l’origine de la détermination de l’efficacité présynaptique demeurent obscurs. Également, la plasticité synaptique reste encore mal définie au niveau glial, limitant, de ce fait, notre compréhension de l’intégration de l’information. Pourtant, la dernière décennie a mené à une redéfinition du rôle des cellules gliales. Autrefois reléguées à un rôle de support passif aux neurones, elles sont désormais reconnues comme étant impliquées dans la régulation de la neurotransmission. Notamment, à la jonction neuromusculaire (JNM), les cellules de Schwann périsynaptiques (CSPs) sont reconnues pour moduler l’efficacité présynaptique et les phénomènes de plasticité. Un tel rôle actif dans la modulation de la neurotransmission implique cependant que les CSPs soient en mesure de s’adapter aux besoins changeants des JNMs auxquelles elles sont associées. La plasticité synaptique devrait donc sous-tendre une forme de plasticité gliale. Nous savons, en effet, que la JNM est capable de modifications tant morphologiques que physiologiques en réponse à des altérations de l'activité synaptique. Par exemple, la stimulation chronique des terminaisons nerveuses entraîne une diminution persistante de l’efficacité présynaptique et une augmentation de la résistance à la dépression. À l’opposé, le blocage chronique des récepteurs nicotiniques entraîne une augmentation prolongée de l’efficacité présynaptique. Aussi, compte tenu que les CSPs détectent et répondent à la neurotransmission et qu’elles réagissent à certains stimuli environnementaux par des changements morphologiques, physiologiques et d’expression génique, nous proposons que le changement d'efficacité présynaptique imposé à la synapse, soit par une stimulation nerveuse chronique ou par blocage chronique des récepteurs nicotiniques, résulte en une adaptation des propriétés des CSPs. Cette thèse propose donc d’étudier, en parallèle, la plasticité présynaptique et gliale à long-terme, en réponse à un changement chronique de l’activité synaptique, à la JNM d’amphibien. Nos résultats démontrent les adaptations présynaptiques de l’efficacité présynaptique, des phénomènes de plasticité à court-terme, du contenu mitochondrial et de la signalisation calcique. De même, ils révèlent différentes adaptations gliales, notamment au niveau de la sensibilité des CSPs aux neurotransmetteurs et des propriétés de leur réponse calcique. Les adaptations présynaptiques et gliales sont discutées, en parallèle, en termes de mécanismes et de fonctions possibles dans la régulation de la neurotransmission. Nos travaux confirment donc la coïncidence de la plasticité présynaptique et gliale et, en ce sens, soulèvent l’importance des adaptations gliales pour le maintien de la fonction synaptique.

Modulation différentielle par la privation de sommeil des processus attentionnels frontaux et pariétaux: une étude de potentiels évoqués cognitifs

L’objectif de la présente étude visait à évaluer les effets différentiels de la privation de sommeil (PS) sur le fonctionnement cognitif sous-tendu par les substrats cérébraux distincts, impliqués dans le réseau fronto-pariétal attentionnel, lors de l’administration d’une tâche simple et de courte durée. Les potentiels évoqués cognitifs, avec sites d’enregistrement multiples, ont été prévilégiés afin d’apprécier les effets de la PS sur l’activité cognitive rapide et ses corrélats topographiques. Le matin suivant une PS totale d’une durée de 24 heures et suivant une nuit de sommeil normale, vingt participants ont exécuté une tâche oddball visuelle à 3 stimuli. L’amplitude et la latence ont été analysées pour la P200 et la N200 à titre d’indices frontaux, tandis que la P300 a été analysée, à titre de composante à contribution à la fois frontale et pariétale. Suite à la PS, une augmentation non spécifique de l’amplitude de la P200 frontale à l’hémisphère gauche, ainsi qu’une perte de latéralisation spécifique à la présentation des stimuli cibles, ont été observées. À l’opposé, l’amplitude de la P300 était réduite de façon prédominante dans la région pariétale pour les stimuli cibles. Enfin, un délai de latence non spécifique pour la N200 et la P300, ainsi qu’une atteinte de la performance (temps de réaction ralentis et nombre d’erreurs plus élevé) ont également été objectivées. Les résultats confirment qu’une PS de durée modérée entraîne une altération des processus attentionnels pouvant être objectivée à la fois par les mesures comportementales et électrophysiologiques. Ces modifications sont présentes à toutes les étapes de traitement, tel que démontré par les effets touchant la P200, la N200 et la P300. Qui plus est, la PS affecte différemment les composantes à prédominance frontale et pariétale.