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See detailA multicomponent exploration of verbal short-term storage deficits in normal aging and Alzheimer’s disease
Peters, Frédéric; Majerus, Steve ULg; Olivier, Laurence et al

in Journal of Clinical & Experimental Neuropsychology (2007), 29(4), 405-417

Although many studies have shown diminished performance in verbal short-term memory tasks in normal aging and Alzheimer's disease (AD), the cognitive processes responsible for this verbal short-term ... [more ▼]

Although many studies have shown diminished performance in verbal short-term memory tasks in normal aging and Alzheimer's disease (AD), the cognitive processes responsible for this verbal short-term storage (STS) impairment are still unclear for both populations. We explored verbal STS functioning in patients with AD, elderly participants, and young participants, by investigating a series of processes that could underlie STS impairments in normal elderly and AD populations. The processes we investigated were (a) the influence of lexical and sublexical language knowledge on short-term storage performance, (b) functioning of the phonological loop component via word length and phonological similarity effects, and (c) executive control processes (coordination and integration). For the AD and elderly groups, the influence of language knowledge on verbal STS performance and the functioning of the phonological loop were preserved. In contrast, the AD group showed deficits for coordination and integration processes. Our results suggest that the verbal STS deficit observed in AD patients is related to impaired executive control processes. On the other hand, language-related processes underlying passive storage capacity seem to be preserved. [less ▲]

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See detailSleep-related hippocampo-cortical interplay during emotional memory recollection.
Sterpenich, Virginie ULg; Albouy, Geneviève ULg; Boly, Mélanie ULg et al

in PLoS Biology (2007), 5(11), 282

Emotional events are usually better remembered than neutral ones. This effect is mediated in part by a modulation of the hippocampus by the amygdala. Sleep plays a role in the consolidation of declarative ... [more ▼]

Emotional events are usually better remembered than neutral ones. This effect is mediated in part by a modulation of the hippocampus by the amygdala. Sleep plays a role in the consolidation of declarative memory. We examined the impact of sleep and lack of sleep on the consolidation of emotional (negative and positive) memories at the macroscopic systems level. Using functional MRI (fMRI), we compared the neural correlates of successful recollection by humans of emotional and neutral stimuli, 72 h after encoding, with or without total sleep deprivation during the first post-encoding night. In contrast to recollection of neutral and positive stimuli, which was deteriorated by sleep deprivation, similar recollection levels were achieved for negative stimuli in both groups. Successful recollection of emotional stimuli elicited larger responses in the hippocampus and various cortical areas, including the medial prefrontal cortex, in the sleep group than in the sleep deprived group. This effect was consistent across subjects for negative items but depended linearly on individual memory performance for positive items. In addition, the hippocampus and medial prefrontal cortex were functionally more connected during recollection of either negative or positive than neutral items, and more so in sleeping than in sleep-deprived subjects. In the sleep-deprived group, recollection of negative items elicited larger responses in the amygdala and an occipital area than in the sleep group. In contrast, no such difference in brain responses between groups was associated with recollection of positive stimuli. The results suggest that the emotional significance of memories influences their sleep-dependent systems-level consolidation. The recruitment of hippocampo-neocortical networks during recollection is enhanced after sleep and is hindered by sleep deprivation. After sleep deprivation, recollection of negative, potentially dangerous, memories recruits an alternate amygdalo-cortical network, which would keep track of emotional information despite sleep deprivation. [less ▲]

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See detailA Synthesis of Functional Neuroimaging in the Frontal Variant of Frontotemporal Dementia
Salmon, Eric ULg; Garraux, Gaëtan ULg; Collette, Fabienne ULg

in Current Medical Imaging Reviews (2007), 3(2), 117-121

The frontal variant of frontotemporal dementia (fvFTD) is clinically characterized by a disruption of the social behaviour. Frontotemporal decrease of activity on functional imaging is an independent ... [more ▼]

The frontal variant of frontotemporal dementia (fvFTD) is clinically characterized by a disruption of the social behaviour. Frontotemporal decrease of activity on functional imaging is an independent marker of the disease. Principal component analysis of cerebral functional images reveals one ensemble comprising both frontal lobes, and two lateralized clusters comprising temporal and subcallosal frontal regions. Executive dysfunction and verbal difficulties are shown to interact in fvFTD, and they are related to large scale frontal and temporal neural networks in the disease. The neural substrate of the memory impairments in patients with fvFTD is also heterogeneous, since correlations were observed with frontal activity, but also with medial temporal atrophy. Behavioural changes are the hallmarks of fvFTD. Apathy is consistently related to frontal involvement, while disinhibition occurs in patients with predominant posterior orbitofrontal and temporal involvement. The consequences of lateralized brain lesions remain a matter of debate, since impulsive and compulsive behaviour was evenly related to right or left temporal involvement in fvFTD. Those patients know social rules, but they are impaired in assessing the importance of social transgressions and in recognizing emotions. Processing transgressions of social norms results in a complex activation of medial prefrontal, orbitofrontal and temporal regions in control populations. The variable decrease in these regional activities observed in different fvFTD patients would explain their complex, individual social disturbance. [less ▲]

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See detailMémoire de travail et vieillissement normal.
Collette, Fabienne ULg; Péters, Fréderic; Hogge, Michaël et al

in Aubin, Ghislaine; Coyette, Françoise; Pradat-Diehl, Pascale (Eds.) et al Neuropsychologie de la mémoire de travail (2007)

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See detailHere I am: the cortical correlates of visual self-recognition.
Devue, Christel ULg; Collette, Fabienne ULg; Balteau, Evelyne ULg et al

in Brain Research (2007), 1143

Recently, interest in the neural correlates of self-recognition has grown. Most studies concentrate on self-face recognition. However, there is a lack of convergence as to precise neuroanatomical ... [more ▼]

Recently, interest in the neural correlates of self-recognition has grown. Most studies concentrate on self-face recognition. However, there is a lack of convergence as to precise neuroanatomical locations underlying self-face recognition. In addition, recognition of familiar persons from bodies has been relatively neglected. In the present study, cerebral activity while participants performed a task in which they had to indicate the real appearance of themselves and of a gender-matched close colleague among intact and altered pictures of faces and bodies was measured. The right frontal cortex and the insula were found to be the main regions specifically implicated in visual self-recognition compared with visual processing of other highly familiar persons. Moreover, the right anterior insula along with the right anterior cingulate seemed to play a role in the integration of information about oneself independently of the stimulus domain. The processing of self-related pictures was also compared to scrambled versions of these pictures. Results showed that different areas of the occipito-temporal cortex were more or less recruited depending on whether a face or a body was perceived, as it has already been reported by several recent studies. The implication of present findings for a general framework of person identification is discussed. [less ▲]

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See detailIs Alzheimer's disease a disconnection syndrome? Evidence from a crossmodal audio-visual illusory experiment
Delbeuck, Xavier; Collette, Fabienne ULg; Van der Linden, Martial ULg

in Neuropsychologia (2007), 45(14), 3315-3323

In Alzheimer's disease (AD), loss of connectivity in the patient's brain has been evidenced by a range of electrophysiological and neuroimaging studies. However, few neuropsychological research projects ... [more ▼]

In Alzheimer's disease (AD), loss of connectivity in the patient's brain has been evidenced by a range of electrophysiological and neuroimaging studies. However, few neuropsychological research projects have sought to interpret the cognitive modifications following the appearance of AD in terms of a disconnection syndrome. In this paper, we sought to investigate brain connectivity in AD via the study of a crossmodal effect. More precisely, we examined the integration of auditory and visual speech information (the McGurk effect) in AD patients and matched control subjects. Our results revealed impaired crossmodal integration during speech perception in AD, which was not associated with disturbances in the separate processing of auditory and visual speech stimuli. In conclusion, our data suggest the occurrence of a specific, audio-visual integration deficit in AD, which might be the consequence of a connectivity breakdown and corroborate the observation from other studies of crossmodal deficits between the auditory and visual modalities in this population. (C) 2007 Elsevier Ltd. All rights reserved. [less ▲]

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See detailFonctionnement inhibiteur dans le vieillissement normal et pathologique
Collette, Fabienne ULg

Conference (2006, September)

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See detailThe locus ceruleus is involved in the successful retrieval of emotional memories in humans
Sterpenich, Virginie ULg; D'Argembeau, Arnaud ULg; Desseilles, Martin ULg et al

in Journal of Neuroscience (2006), 26(28), 7416-7423

Emotional memories are better remembered than neutral ones. The amygdala is involved in this enhancement not only by modulating the hippocampal activity, but possibly also by modulating central arousal ... [more ▼]

Emotional memories are better remembered than neutral ones. The amygdala is involved in this enhancement not only by modulating the hippocampal activity, but possibly also by modulating central arousal. Using functional magnetic resonance imaging, we analyzed the retrieval of neutral faces encoded in emotional or neutral contexts. The pupillary size measured during encoding was used as a modulator of brain responses during retrieval. The interaction between emotion and memory showed significant responses in a set of areas, including the amygdala and parahippocampal gyrus. These areas responded significantly more for correctly remembered faces encoded in an emotional, compared with neutral, context. The same interaction conducted on responses modulated by the pupillary size revealed an area of the dorsal tegmentum of the ponto-mesencephalic region, consistent with the locus ceruleus. Moreover, a psychophysiological interaction showed that amygdalar responses were more tightly related to those of the locus ceruleus when remembering faces that had been encoded in an emotional, rather than neutral, context. These findings suggest that the restoration of a central arousal similar to encoding takes part in the successful retrieval of neutral events learned in an emotional context. [less ▲]

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See detailNeural correlates of anosognosia for cognitive impairment in Alzheimer's disease
Salmon, Eric ULg; Perani, D.; Herholz, K. et al

in Human Brain Mapping (2006), 27(7), 588-597

We explored the neural substrate of anosognosia for cognitive impairment in Alzheimer's disease (AD). Two hundred nine patients with mild to moderate dementia and their caregivers assessed patients ... [more ▼]

We explored the neural substrate of anosognosia for cognitive impairment in Alzheimer's disease (AD). Two hundred nine patients with mild to moderate dementia and their caregivers assessed patients' cognitive impairment by answering a structured questionnaire. Subjects rated 13 cognitive domains as not impaired or associated with mild, moderate, severe, or very severe difficulties, and a sum score was calculated. Two measures of anosognosia were derived. A patient's self assessment, unconfounded by objective measurements of cognitive deficits such as dementia severity and episodic memory impairment, provided an estimate of impaired self-evaluative judgment about cognition in AD. Impaired self-evaluation was related to a decrease in brain metabolism measured with 18F-2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) in orbital prefrontal cortex and in medial temporal structures. In a cognitive model of anosognosia, medial temporal dysfunction might impair a comparison mechanism between current information on cognition and personal knowledge. Hypoactivity in orbitofrontal cortex may not allow AD patients to update the qualitative judgment associated with their impaired cognitive abilities. Caregivers perceived greater cognitive impairments than patients did. The discrepancy score between caregiver's and patient's evaluations, an other measure of anosognosia, was negatively related to metabolic activity located in the temporoparietal junction, consistent with an impairment of self-referential processes and perspective taking in AD. [less ▲]

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See detailThe role of selective rehearsal and attentional inhibition in directed forgetting
Feyers, Dorothée ULg; Hogge, Michaël; Collette, Fabienne ULg

Poster (2006, May 19)

The directed forgetting paradigm has been extensively used to assess how subjects intentionally limit the future expression of specific memory content. In the item method, subjects are given a list of ... [more ▼]

The directed forgetting paradigm has been extensively used to assess how subjects intentionally limit the future expression of specific memory content. In the item method, subjects are given a list of words with the instruction to remember every item followed by a “remember” cue (to-be-remembered items or TBR) and to forget items followed by a “forget” cue (to-be-forgotten items or TBF). Typically, TBR items are better recalled or recognized than TBF items when subjects are subsequently tested on all presented words, regardless of study instructions. However, it is currently not clear if this directed forgetting effect is due to a selective rehearsal of TBR items or to an attentional inhibition of TBF items. In the present study, the performance of two groups of subjects that performed a directed forgetting task with or without articulatory suppression was compared. Indeed, if selective rehearsal is responsible of the directed forgetting effect, the effect should disappear when subjects are not allowed to rehearse TBR items because of the articulatory suppression instruction. Results showed an equivalent directed forgetting effect between the two groups on a recognition task. These results suggest that selective rehearsal is not the major determinant of the directed forgetting effect. [less ▲]

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See detailExploration of the neural substrates of executive functioning by functional neuroimaging
Collette, Fabienne ULg; Hogge, Michaël; Salmon, Eric ULg et al

in Neuroscience (2006), 139(1), 209-221

This review presents neuroimaging studies that have explored the cerebral substrates of executive functioning. These studies have demonstrated that different executive functions not only recruit various ... [more ▼]

This review presents neuroimaging studies that have explored the cerebral substrates of executive functioning. These studies have demonstrated that different executive functions not only recruit various frontal areas but also depend upon posterior (mainly parietal) regions. These results are in accordance with the hypothesis that executive functioning relies on a distributed cerebral network that is not restricted to anterior cerebral areas. However, there exists an important heterogeneity in the cerebral areas associated with these different processes, and also between different tasks assessing the same process. Since these discrepant results could be due to the paradigms used (subtraction designs), recent results obtained with conjunction and interaction analyses are presented, which confirm the role of parietal areas in executive functioning and also demonstrate the existence of some specificity in the neural substrates of the executive processes of updating, shifting and inhibition. Finally, functional magnetic resonance imaging studies show that the activity in cerebral areas involved in executive tasks can be transient or sustained. Consequently, to better characterize the functional role of areas associated with executive functioning, it is important to take into account not only the localization of cerebral activity but also the temporal pattern of this activity. [less ▲]

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See detailDecomposition of metabolic brain clusters in the frontal variant of frontotemporal dementia
Salmon, Eric ULg; Kerrouche, Nacer; Herholz, Karl et al

in NeuroImage (2006), 30(3), 871-878

Previous studies that measured brain activity in frontotemporal dementia (FTD) used univariate analyses, examining each region of interest separately. We explored in a multicenter European research ... [more ▼]

Previous studies that measured brain activity in frontotemporal dementia (FTD) used univariate analyses, examining each region of interest separately. We explored in a multicenter European research program the principal brain clusters characterized by a common variability in cerebral metabolism in FTD. Seventy patients with frontal variant (fv) FTD were selected according to international clinical recommendations; principal component analysis (PCA) was performed on FDG-PET metabolic images, looking for covariance clusters in this large population. A first metabolic cluster included most of the lateral and medial prefrontal cortex, bilaterally; PC1 scores correlated with performances on memory and executive neuropsychological tasks. Moreover, FDG-PET images in fv-FTD were further characterized by a metabolic covariance in two clusters comprising the subcallosal medial frontal region, the temporal pole, medial temporal structures and the striatum, separately in the left and in the right hemisphere. The study provides original data-driven arguments for metabolic involvement of separate brain clusters in the rostral limbic system, corresponding to pathological poles differentially affected in each FTD patient. [less ▲]

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See detailMémoire de travail et administrateur central: conceptions théoriques récentes
Collette, Fabienne ULg

Scientific conference (2006, April)

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See detailHippocampal response at training promotes insight after sleep
Darsaud, Annabelle; Balteau, Evelyne ULg; Desseilles, Martin ULg et al

in NeuroImage (2006), 31(Suppl. 1),

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See detailThe left intraparietal sulcus and verbal short-term memory: Focus of attention or serial order ?
Majerus, Steve ULg; Poncelet, Martine ULg; Van der Linden, Martial ULg et al

in Neuroimage (2006), 32(2), 880-891

One of the most consistently activated regions during verbal short-term memory (STM) tasks is the left intraparietal sulcus (IPS). However, its precise role remains a matter of debate. While some authors ... [more ▼]

One of the most consistently activated regions during verbal short-term memory (STM) tasks is the left intraparietal sulcus (IPS). However, its precise role remains a matter of debate. While some authors consider the IPS to be a specific store for serial order information, other data suggest that it serves a more general function of attentional focalization. In the current fMRI experiment, we investigated these two hypotheses by presenting different verbal STM conditions that probed recognition for word identity or word order and by assessing functional connectivity of the left IPS with distant brain areas. If the IPS has a role of attentional focalization, then it should be involved in both order and item conditions, but it should be connected to different brain regions, depending on the neural substrates involved in processing the different types of information (order versus phonological/orthographic) to be remembered in the item and order STM conditions. We observed that the left IPS was activated in both order and item STM conditions but for different reasons: during order STM, the left IPS was functionally connected to serial/temporal order processing areas in the right IPS, premotor and cerebellar cortices, while during item STM, the left IPS was connected to phonological and orthographic processing areas in the superior temporal and fusiform gyri. Our data support a position considering that the left IPS acts as an attentional modulator of distant neural networks which themselves are specialized in processing order or language representations. More generally, they strengthen attention-based accounts of verbal STM. [less ▲]

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See detailOrbitofrontal dysfunction related to both apathy and disinhibition in frontotemporal dementia
Peters, Frederic; Perani, Daniela; Herholz, Karl et al

in Dementia & Geriatric Cognitive Disorders (2006), 21(5-6), 373-379

Orbitofrontal metabolic impairment is characteristic of the frontal variant of frontotemporal dementia (fv-FTD), as are early changes in emotional and social conduct. Two main types of behavioral ... [more ▼]

Orbitofrontal metabolic impairment is characteristic of the frontal variant of frontotemporal dementia (fv-FTD), as are early changes in emotional and social conduct. Two main types of behavioral disturbances have been distinguished in fv-FTD patients: apathetic and disinhibited manifestations. In this study, we searched for relationships between brain metabolism and presence of apathetic or disinhibited behavior. Metabolic activity and behavioral data were collected in 41 fv-FTD patients from European PET centers. A conjunction analysis of the PET data showed an expected impairment of metabolic activity in the anterior cingulate, ventromedial and orbital prefrontal cortex, the dorsolateral prefrontal cortex and the left anterior insula in fv-FTD subjects compared to matched controls. A correlation was observed between disinhibition scores on the Neuropsychiatric Inventory scale and a cluster of voxels located in the posterior orbitofrontal cortex ( 6, 28, - 24). Comparison of brain activity between apathetic and nonapathetic fv-FTD patients from two centers also revealed a specific involvement of the posterior orbitofrontal cortex in apathetic subjects ( 4, 22, - 22). The results confirm that the main cerebral metabolic impairment in fv-FTD patients affects areas specializing in emotional evaluation and demonstrate that decreased orbitofrontal activity is related to both disinhibited and apathetic syndromes in fv-FTD. Copyright (C) 2006 S. Karger AG, Basel. [less ▲]

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