Influence des processus attentionnels sur le fonctionnement exécutif lors du vieillissement normal

Conference (2008, September 04)

Neural network involved in self-judgment in young and elderly adults

Poster (2008, May 29)

In agreement with the literature, we have recently observed that the ventro-medial prefrontal cortex (VMPFC) is activated both in young and elderly subjects during a adjective judgment task requiring ... [more ▼]

In agreement with the literature, we have recently observed that the ventro-medial prefrontal cortex (VMPFC) is activated both in young and elderly subjects during a adjective judgment task requiring judgment about self vs. other in the context of a first (1PP) or third (3PP) perspective-taking (Ruby et al., submitted). Here, we have performed functional connectivity analyses to determine the network of cerebral areas associated to the performance of young and elderly subjects. <br />Results indicate that, in the 1PP condition, activity of the VMPFC is related to the inferior frontal gyrus, parahippocampal gyrus in elderly but to the occipital cortex only in young subjects. In the 3PP condition, functional connectivity exist between the VMPFC and medial frontal gyrus, inferior frontal gyrus and superior temporal areas in elderly, but with occipital and parietal areas only in young subjects. <br />The cerebral areas associated to VMPFC activity in young subjects were previously described as involved both in autobiographical memory retrieval and mentalizing processes. With regard to elderly, the cerebral network evidenced is related to retrieval of semantic and episodic memories (parahippocampal and superior temporal) but also to the attribution of emotional valence to the adjectives (inferior frontal) and perspective taking (medial frontal gyrus). <br />These results indicate (1) that the VMPFC is connected to a larger cerebral network in elderly than in young subjects during self judgements; (2) that young subjects perform the task on the basis of autobiographical information retrieval only, while elderly subjects use supplementary, more reflexive, cognitive processes. [less ▲]

Functional imaging of cognition in Alzheimer's disease using positron emission tomography

in Neuropsychologia (2008), 46(6), 1613-1623

Positron emission tomography in Alzheimer's disease (AD) demonstrates a metabolic decrease, predominantly in associative posterior cortices (comprising the posterior cingulate cortex), and also involving ... [more ▼]

Positron emission tomography in Alzheimer's disease (AD) demonstrates a metabolic decrease, predominantly in associative posterior cortices (comprising the posterior cingulate cortex), and also involving medial temporal structures and frontal regions at a lesser degree. The level of activity in this wide network is roughly correlated with dementia severity, but several confounds (such as age, education or subcortical ischemic lesions) may influence the brain-behaviour relationship. Univariate analyses allow one to segregate brain regions that are particularly closely related to specific neuropsychological performances. For example, a relationship was established between the activity in lateral associative cortices and semantic performance in AD. The role of semantic capacities (subserved by temporal or parietal regions) in episodic memory tasks was also emphasized. The residual activity in medial temporal structures was related to episodic memory abilities, as measured by free recall performance, cued recall ability and recognition accuracy. More generally, AD patients' performance on episodic memory tasks was correlated with the metabolism in several structures of Papez's circuit (including the medial temporal and posterior cingulate regions). Multivariate analyses should provide complementary information on impaired metabolic covariance in functional networks of brain regions and the consequences for AD patients' cognitive performance. More longitudinal studies are being conducted that should tell us more about the prognostic value of initial metabolic impairment and the neural correlates of progressive deterioration of cognitive performance in AD. [less ▲]

Neural network involved in young and elderly adults

in Proceedings of the Cognitive Aging Conference (2008, April 11)

In agreement with the literature, we have recently observed that the ventro-medial prefrontal cortex (VMPFC) is activated both in young and elderly subjects during a adjective judgment task requiring ... [more ▼]

In agreement with the literature, we have recently observed that the ventro-medial prefrontal cortex (VMPFC) is activated both in young and elderly subjects during a adjective judgment task requiring judgment about self vs. other in the context of a first (1PP) or third (3PP) perspective-taking (Ruby et al., submitted). Here, we have performed functional connectivity analyses to determine the network of cerebral areas associated to the performance of young and elderly subjects. Results indicate that, in the 1PP condition, activity of the VMPFC is related to the medial orbito-frontal, posterior and inferior temporal and parietal areas in elderly, but to the occipital cortex only in young subjects. In the 3PP condition, functional connectivity exist between the VMPFC and posterior temporal and lateral orbito-frontal areas in elderly, but with occipital and parietal areas only in young subjects. The cerebral areas associated to VMPFC activity in young subjects were previously described as involved both in autobiographic memory retrieval and mentalizing processes. With regard to elderly, the cerebral network evidenced is related to autobiographic memory retrieval (parietal and temporal areas) but also to the attribution of emotional valence to the adjectives (medial orbito-frontal) and perspective taking both in 1PP and 3PP conditions (lateral orbito-frontal). These results indicate (1) that the VMPFC is connected to a larger cerebral network in elderly than in young subjects during self judgements; (2) that young subjects perform the task on the basis of autobiographical information retrieval only, while elderly subjects use supplementary, more reflexive, cognitive processes. [less ▲]

Chronotype-dependent performance modulation according to time of day : a functional neuroimaging approach

in NeuroImage (2008), 41(Suppl. 1),

Exploration of memory and executive functioning in frontotemporal dementia

Conference (2008)

Metabolic correlates of controlled memory processes in very early Alzheimer’s disease and stable questionable Alzheimer’s disease

Conference (2008)

Metabolic correlates of clinical heterogeneity in questionable Alzheimer’s disease

in Neurobiology of Aging (2008), 29

Thirty-four subjects with questionable Alzheimer's disease (QAD) were included in a 3-year prospective study and underwent neuropsychological testing and measurement of brain metabolism using FDG-PET at ... [more ▼]

Thirty-four subjects with questionable Alzheimer's disease (QAD) were included in a 3-year prospective study and underwent neuropsychological testing and measurement of brain metabolism using FDG-PET at entry. Seventeen patients (50%) did not convert to AD during the follow-up period. Compared to elderly controls of similar age, the cerebral activity of non-converters was reduced in the dorsolateral prefrontal cortex. Moreover, the variability of metabolism in the posterior cingulate cortex was related to their visuospatial memory performance, while disparity in parietal activity was related to their verbal memory performance. These results demonstrate the cerebral metabolic heterogeneity of patients with QAD. Initial functional images of converters showed that activity was already impaired in the posterior cingulate, lateral temporal cortex, anterior cingulate and orbitofrontal cortex. This metabolic pattern is consistent with a pre-dementia stage of AD, and highlights the fact that significant frontal metabolic involvement may be associated with impaired activity in posterior associative cortices in very early AD. [less ▲]

Directed forgetting and aging: the role of retrieval processes, processing speed, and proactive interference.

in Neuropsychology, Development, and Cognition. Section B, Aging, Neuropsychology and Cognition (2008), 15(4), 471-91

The directed forgetting effect obtained with the item method is supposed to depend on both selective rehearsal of to-be-remembered (TBR) items and attentional inhibition of to-be-forgotten (TBF) items. In ... [more ▼]

The directed forgetting effect obtained with the item method is supposed to depend on both selective rehearsal of to-be-remembered (TBR) items and attentional inhibition of to-be-forgotten (TBF) items. In this study, we investigated the locus of the directed forgetting deficit in older adults by exploring the influence of recollection and familiarity-based retrieval processes on age-related differences in directed forgetting. Moreover, we explored the influence of processing speed, short-term memory capacity, thought suppression tendencies, and sensitivity to proactive interference on performance. The results indicated that older adults' directed forgetting difficulties are due to decreased recollection of TBR items, associated with increased automatic retrieval of TBF items. Moreover, processing speed and proactive interference appeared to be responsible for the decreased recall of TBR items. [less ▲]

Self-reflection across time: cortical midline structures differentiate between present and past selves

in Social Cognitive and Affective Neuroscience (2008), 3(3), 244-252

The processing of personal changes across time and the ability to differentiate between representations of present and past selves are crucial for developing a mature sense of identity. In this study, we ... [more ▼]

The processing of personal changes across time and the ability to differentiate between representations of present and past selves are crucial for developing a mature sense of identity. In this study, we explored the neural correlates of self-reflection across time using functional magnetic resonance imaging (fMRI). College undergraduates were asked to reflect on their own psychological characteristics and those of an intimate other, for both the present time period (i.e. at college) and a past time period (i.e. high school years) that involved significant personal changes. Cortical midline structures (CMS) were commonly recruited by the four reflective tasks (reflecting on the present self, past self, present other and past other), relative to a control condition (making valence judgments). More importantly, however, the degree of activity in CMS also varied significantly according to the target of reflection, with the ventral and dorsal medial prefrontal cortex and the posterior cingulate cortex being more recruited when reflecting on the present self than when reflecting on the past self or when reflecting on the other person. These findings suggest that CMS may contribute to differentiate between representations of present and past selves. [less ▲]