Martial Van der Linden

Experience-dependent changes in cerebral activation during human Rem sleep

The function of rapid-eye-movement (REM) sleep is still unknown. One prevailing hypothesis suggests that REM sleep is important in processing memory traces. Here, using positron emission tomography (PET) and regional cerebral blood flow measurements, we show that waking experience influences regional brain activity during subsequent sleep. Several brain areas activated during the execution of a serial reaction time task during wakefulness were significantly more active during REM sleep in subjects previously trained on the task than in non-trained subjects. These results support the hypothesis that memory traces are processed during REM sleep in humans.

Brain imaging of the central executive component of working memory

This review presents neuroimaging studies which have explored the cerebral substrates of the central executive component of the working memory model proposed by Baddeley and Hitch [Working memory (1986); Recent advances in learning and motivation (1974)]. These studies have demonstrated that different executive functions (manipulating and updating of information, dual-task coordination, inhibition and shifting processes) not only recruit various frontal areas, but also depend upon posterior (mainly parietal) regions. Such results are in agreement with the hypothesis that executive functions rely on a distributed cerebral network not restricted to anterior cerebral areas. Moreover, the intervention of similar prefrontal regions in a large number of executive tasks suggests that the central executive functioning must be understood in terms of different interactions between a network of regions rather than in terms of a specific association between one region and one higher-level cognitive process.

Self-referential reflective activity and its relationship with rest: a PET study.

This study used positron emission tomography (PET) to identify the brain substrate of self-referential reflective activity and to investigate its relationship with brain areas that are active during the resting state. Thirteen healthy volunteers performed reflective tasks pertaining to three different matters (the self, another person, and social issues) while they were scanned. Rest scans were also acquired, in which subjects were asked to simply relax and not think in a systematic way. The mental activity experienced during each scan was assessed with rating scales. The results showed that, although self-referential thoughts were most frequent during the self-referential task, some self-referential reflective activity also occurred during rest. Compared to rest, performing the reflective tasks was associated with increased blood flow in the dorsomedial prefrontal cortex, the left anterior middle temporal gyrus, the temporal pole bilaterally, and the right cerebellum; there was a decrease of blood flow in right prefrontal regions and in medial and right lateral parietal regions. In addition, the ventromedial prefrontal cortex (VMPFC) (1) was more active during the self-referential reflective task than during the other two reflective tasks, (2) showed common activation during rest and the self-referential task, and (3) showed a correlation between cerebral metabolism and the amount of self-referential processing. It is suggested that the VMPFC is crucial for representing knowledge pertaining to the self and that this is an important function of the resting state.

Alzheimer' Disease as a Disconnection Syndrome?

This paper reviews the growing amount of evidence supporting the hypothesis that Alzheimers disease includes a disconnection syndrome. This evidence came mainly from neuropathological, electrophysiological, and neuroimaging studies. Moreover, a few recent neuropsychological studies have also explored the effects of a disconnection between cerebral areas on cognitive functioning. Finally, and more generally, the contribution of this interpretation to the understanding of Alzheimers disease cognitive deficits is considered.

Decision-making and impulse control after frontal lobe injuries

Purpose of reviewFor a long time, the prefrontal cortex has been considered a ‘nonfunctional’ brain area, and understanding its function has lagged behind other areas. This is no longer true since appreciation of the vital role that this brain region plays in adaptive behaviors, and especially decision-making, is now evident more than ever. The present review highlights recent progress made in this area of research. Recent findingsDecision-making is a term often referred to in the psychological literature as one of the ‘executive functions’ that play a role in managing (like an executive) other cognitive functions, such as memory, attention, and language. Considerable research efforts have been directed towards differentiating various processes of executive functions, but much of this effort in the past has focused on the dorsolateral prefrontal cortex sector. Here we will review findings that address decision-making and its link to the ventromedial prefrontal cortex. SummaryDecision-making impairments as encountered in neurological and psychiatric patients are costly in terms of individual human suffering and in financial terms. In addition to its obvious value in advancing fundamental knowledge in neuroscience, understanding the neural mechanisms of decision-making is likely to have important practical consequences, including the understanding and management of neuropsychiatric disorders such as addiction, as well as the management of a considerable number of elderly people suffering from a decline in cognitive functions critical for decision-making, in spite of relatively intact memory and general intellect, which impact real-life matters that are important to themselves and their family.

Exploring the Unity and Diversity of the Neural Substrates of Executive Functioning

Previous studies exploring the neural substrates of executive functioning used task‐specific analyses, which might not be the most appropriate approach due to the difficulty of precisely isolating executive functions. Consequently, the aim of this study was to use positron emission tomography (PET) to reexamine by conjunction and interaction paradigms the cerebral areas associated with three executive processes (updating, shifting, and inhibition). Three conjunction analyses allowed us to isolate the cerebral areas common to tasks selected to tap into the same executive process. A global conjunction analysis demonstrated that foci of activation common to all tasks were observed in the right intraparietal sulcus, the left superior parietal gyrus, and at a lower statistical threshold, the left lateral prefrontal cortex. These regions thus seem to play a general role in executive functioning. The right intraparietal sulcus seems to play a role in selective attention to relevant stimuli and in suppression of irrelevant information. The left superior parietal region is involved in amodal switching/integration processes. One hypothesis regarding the functional role of the lateral prefrontal cortex is that monitoring and temporal organization of cognitive processes are necessary to carry out ongoing tasks. Finally, interaction analyses showed that specific prefrontal cerebral areas were associated with each executive process. The results of this neuroimaging study are in agreement with cognitive studies demonstrating that executive functioning is characterized by both unity and diversity of processes. Hum. Brain Mapp, 2005.

Individual differences in the phenomenology of mental time travel: The effect of vivid visual imagery and emotion regulation strategies

It has been claimed that the ability to remember the past and the ability to project oneself into the future are intimately related. We sought support for this proposition by examining whether individual differences in dimensions that have been shown to affect memory for past events similarly influence the experience of projecting oneself into the future. We found that individuals with a higher capacity for visual imagery experienced more visual and other sensory details both when remembering past events and when imagining future events. In addition, individuals who habitually use suppression to regulate their emotions experienced fewer sensory, contextual, and emotional details when representing both past and future events, while the use of reappraisal had no effect on either kind of events. These findings are consistent with the view that mental time travel into the past and into the future relies on similar mechanisms.

French Validation of the Internet Addiction Test

The main goal of the present study is to investigate the psychometric properties of a French version of the Internet Addiction Test (IAT) and to assess its relationship with both time spent on Internet and online gaming. The French version of the Youngs Internet Addiction Test (IAT) was administered to a sample of 246 adults. Exploratory and confirmatory analyses were carried out. We discovered that a one-factor model of the IAT has good psychometric properties and fits the data well, which is not the case of a six-factor model as found in previous studies using exploratory methods. Correlation analysis revealed positive significant relationships between IAT scores and both the daily duration of Internet use and the fact of being an online player. In addition, younger people scored higher on the IAT. The one-factor model found in this study has to be replicated in other IAT language versions.

The contribution of recollection and familiarity to recognition memory: a study of the effects of test format and aging.

Whether the format of a recognition memory task influences the contribution of recollection and familiarity to performance is a matter of debate. The authors investigated this issue by comparing the performance of 64 young (mean age = 21.7 years; mean education = 14.5 years) and 62 older participants (mean age = 64.4 years; mean education = 14.2 years) on a yes-no and a forced-choice recognition task for unfamiliar faces using the remember-know-guess procedure. Familiarity contributed more to forced-choice than to yes-no performance. Moreover, older participants, who showed a decrease in recollection together with an increase in familiarity, performed better on the forced-choice task than on the yes-no task, whereas younger participants showed the opposite pattern.

Executive dysfunction in Alzheimer's disease.

Executive functioning was examined in 20 patients with Alzheimers disease (AD) and 20 normal elderly subjects. The results showed that AD patients present lower performance compared to control subjects in all executive tasks, confirming that some executive deficits may be present in the first stages of the disease. A factorial analysis suggested that these deficits can be related to two domains of the executive functions: the inhibition abilities and the capacity to co-ordinate simultaneously storage and processing of information. Moreover, the performance on these factors is correlated to different anterior and posterior cortical areas.