References of "Collette, Fabienne"
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See detailVerbal Learning in Alzheimer’s disease and Mild Cognitive Impairment: neuroanatomic correlates of acquisition and consolidation performances
Genon, Sarah ULg; Collette, Fabienne ULg; Moulin, Christopher et al

in Proceedings of the Annual Meeting of the Belgian Association for Psychological Sciences (2010)

The aim of this study was to examine correlations between impaired memory acquisition/consolidation and brain metabolism at rest in Alzheimer’s disease. 44 confirmed Alzheimer patients (AD), 16 patients ... [more ▼]

The aim of this study was to examine correlations between impaired memory acquisition/consolidation and brain metabolism at rest in Alzheimer’s disease. 44 confirmed Alzheimer patients (AD), 16 patients with mild cognitive impairment (MCI) who converted to AD (MCI-C) (4-8 years of follow-up), 15 MCI patients who remained stable and 12 healthy elderly controls were administered the California Verbal Learning Task (CVLT) at entry. Acquisition and consolidation memory scores were calculated respectively as mean gained and total lost access across the 5 study-test trials (p = 0.05). Brain metabolism was measured by 18FDG-PET. Cognitive-metabolic correlations were performed with SPM8 (p<0.05 uncorrected). Mean gained access was significantly lower in the AD group than in the control and MCI-S group and was significantly lower in the MCI-C group than in the control group. Mean gained access was significantly correlated to metabolism in the left precentral gyrus and IPS fondus in the control group, in the left and right inferior parietal lobules in the MCI-S group and in the left hippocampus in the AD group. Total lost access was greater in AD patients compared to control participants. No significant correlation between total lost access and brain metabolism was found. The acquisition process is impaired in AD patients at a very early stage of the disease (MCI-C). This deficit is linked to metabolic changes in a frontoparieto-hippocampal learning network. In addition, consolidation process is specifically impaired in confirmed AD patients, while this deficit was not significantly correlated to brain metabolism in our participant groups. [less ▲]

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

Scientific conference (2009, October 15)

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See detailMémoire épisodique et métamémoire dans la variante comportementale de la démence fronto-temporale
Feyers, Dorothée ULg; Bastin, Christine ULg; Collette, Fabienne ULg et al

Conference (2009, September 28)

Impaired memory performance does not constitute the prominent deficit in frontotemporal dementia (FTD). Nevertheless, it has been suggested that some specific aspects of memory may be disrupted in FTD ... [more ▼]

Impaired memory performance does not constitute the prominent deficit in frontotemporal dementia (FTD). Nevertheless, it has been suggested that some specific aspects of memory may be disrupted in FTD patients, in particular, the ability to consciously recollect the context in which information has been learned (Simons et al., 2002). The aims of the current study was to investigate the states of awareness accompanying recognition memory by asking participants to make Remember/Know/Guess judgments. Concretely, 12 FDT patients and 12 matched healthy participants studied 20 word pairs. During cued recall, each trial consisted of one word from a pair and participants had to try to recall the associated word. Finally, a 5-alternative forced-choice recognition task was given and participants had to say whether they chose a word because they recollected the study context (Remember), they knew they saw the word, without recalling anything else (Know) or they guessed (Guess). Results from the cued recall and recognition parts indicated that FTD recalled less word pairs than the controls, but had similar levels of recognition performance. Nevertheless, FTD patients gave less Remember responses than the controls, and tended to give more Guess responses. To conclude, episodic memory performance in FTD was characterised by impaired self-initiated memory retrieval processes. Although global recognition memory performance was preserved, FTD patients’ memories lacked of autonoetic consciousness and were mainly based on familiarity judgments and guessing. This pattern of results is similar to that found in patients with focal frontal lobe lesions (e.g., Wheeler et al., 1995; Wheeler & Stuss, 2003) and is consistent with the idea that the memory dysfunctions observed in FTD may stem from damage to the prefrontal cortex. [less ▲]

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See detailEvidence for a role of sleep in forgetting of irrelevant information
Collette, Fabienne ULg; Rauchs, Géraldine; Landeau, Brigitte et al

in NeuroImage (2009, June), 47(Suppl 1), 328-

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See detailSpecificity of Inhibitory Deficits in Normal Aging and Alzheimer's Disease
Collette, Fabienne ULg; Schmidt, Christina ULg; Scherrer, Christine et al

in Neurobiology of Aging (2009), 30

Deficits of suppression abilities are frequently observed in normal aging and Alzheimer's disease. However, few studies have explored these deficits in the two populations simultaneously using a large ... [more ▼]

Deficits of suppression abilities are frequently observed in normal aging and Alzheimer's disease. However, few studies have explored these deficits in the two populations simultaneously using a large battery of tasks. The aim of the present study was to explore if the pattern of performance presented by elderly subjects and AD patients is in agreement with theoretical frameworks [Wilson, S.P., Harnishfeger, K.K., 1998. The development of efficient inhibition: Evidence from directed forgetting tasks. Dev. Rev. 18, 86-123; see also Nigg J.T., 2000. On inhibition/disinhibition in developmental psychopathology: views from cognitive and personality psychology and a working inhibition taxonomy. Psychol. Bull. 126, 220-246], distinguishing between the concepts of inhibition (a voluntary suppression of irrelevant information) and interference (an automatic suppression process occurring prior to conscious awareness). The results obtained demonstrated that (1) there is an alteration of the inhibitory process in normal elderly subjects; (2) inhibitory and interference resolution processes are quantitately less efficient in AD, since these patients present a correct performance only for information which leaves weak traces in memory. [less ▲]

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See detailLes capacités d’inhibition dans le vieillissement normal et pathologique
Collette, Fabienne ULg

Scientific conference (2009, March 16)

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See detailMultivariate analysis of cognitive profiles in Alzheimer's disease
Bastin, Christine ULg; Leclercq, Yves ULg; Collette, Fabienne ULg et al

in Proceedings of the 8th bi-annual Meeting of the Belgian Society for Neuroscience (2009)

The neuropsychological profiles of patients with early Alzheimer’s disease (AD) appear to be heterogeneous. In this study, we examined whether this heterogeneity corresponds to the existence of ... [more ▼]

The neuropsychological profiles of patients with early Alzheimer’s disease (AD) appear to be heterogeneous. In this study, we examined whether this heterogeneity corresponds to the existence of cognitively distinct subtypes of AD or rather to impairments along a continuum of performances in different cognitive domains. A large group of 187 AD patients recruited in the European project NEST-DD performed a neuropsychological battery. A factor analysis of cognitive performance identified three factors, which respectively reflected attentional/instrumental function, declarative memory and executive function. Three clustering methods were applied on the factor scores in order to explore the existence of separate groups. The clustering methods indicated that cognitive profiles among the patients were sufficiently variable to identify clusters, but there was continuity between clusters rather than clear-cut subtypes. Moreover, clusters corresponded to various combinations of relatively impaired and preserved functions, suggesting multidimensional distribution within a large population of patients. Finally, clusters of cognitive profiles were characterized by different levels of metabolism in brain regions commonly (but variably) involved or relatively preserved in AD. [less ▲]

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See detailThe neural correlates of verbal short-term memory in Alzheimer's disease: an fMRI study.
Peters, Fréderic; Collette, Fabienne ULg; Degueldre, Christian ULg et al

in Brain : A Journal of Neurology (2009), 132(7), 1833-1846

Although many studies have shown diminished performance in verbal short-term memory tasks in Alzheimer's disease, few studies have explored the neural correlates of impaired verbal short-term memory in ... [more ▼]

Although many studies have shown diminished performance in verbal short-term memory tasks in Alzheimer's disease, few studies have explored the neural correlates of impaired verbal short-term memory in Alzheimer's disease patients. In this fMRI study, we examined alterations in brain activation patterns during a verbal short-term memory recognition task, by differentiating encoding and retrieval phases. Sixteen mild Alzheimer's disease patients and 16 elderly controls were presented with lists of four words followed, after a few seconds, by a probe word. Participants had to judge whether the probe matched one of the items of the memory list. In both groups, the short-term memory task elicited a distributed fronto-parieto-temporal activation that encompassed bilateral inferior frontal, insular, supplementary motor, precentral and postcentral areas, consistent with previous studies of verbal short-term memory in young subjects. Most notably, Alzheimer's disease patients showed reduced activation in several regions during the encoding phase, including the bilateral middle frontal and the left inferior frontal gyri (associated with executive control processes) as well as the transverse temporal gyri (associated with phonological processing). During the recognition phase, we found decreased activation in the left supramarginal gyrus and the right middle frontal gyrus in Alzheimer's disease patients compared with healthy seniors, possibly related to deficits in manipulation and decision processes for phonological information. At the same time, Alzheimer's disease patients showed increased activation in several brain areas, including the left parahippocampus and hippocampus, suggesting that Alzheimer's disease patients may recruit alternative recognition mechanisms when performing a short-term memory task. Overall, our results indicate that Alzheimer's disease patients show differences in the functional networks underlying memory over short delays, mostly in brain areas known to support phonological processing or executive functioning. [less ▲]

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See detailDifferential diagnosis of dementia using functional neuroimaging
Salmon, Eric ULg; Collette, Fabienne ULg; Garraux, Gaëtan ULg

in Jagust, William; D'Esposito, Mark (Eds.) Imaging the aging brain (2009)

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See detailLes corrélats neuronaux de l’acquisition et de la consolidation en mémoire dans la maladie d’Alzheimer et le trouble de mémoire isolé
Genon, Sarah ULg; Collette, Fabienne ULg; Moulin, Christopher et al

in Revue Neurologique (2009), 165

Introduction : Un déficit en mémoire épisodique est caractéristique dans la maladie d’Alzheimer (AD) et chez les patients âgés présentant une altération cognitive légère (MCI). Cette altération peut ... [more ▼]

Introduction : Un déficit en mémoire épisodique est caractéristique dans la maladie d’Alzheimer (AD) et chez les patients âgés présentant une altération cognitive légère (MCI). Cette altération peut s’expliquer par un déficit d’acquisition et/ou un déficit de consolidation. Toutefois, les modifications cérébrales responsables de ces déficits ne sont pas encore parfaitement élucidées. L’objectif de notre étude était de mettre en relation le profil d’apprentissage déficitaire de ces patients avec leur métabolisme cérébral au repos. Méthode : L’épreuve du California Verbal Learning Test (CVLT) a été administrée à 51 patients AD, 18 patients MCI qui sont restés stables (suivi longitudinal de 18 mois, MCI-S), 16 patients MCI qui ont développé la maladie d’Alzheimer (MCI-C) durant les 18 mois de suivi et 12 participants de contrôle. La mesure d’acquisition est la proportion moyenne de gain à travers les 5 essais d’apprentissage du CVLT. La mesure de consolidation est la proportion totale de pertes à travers ces 5 essais. La mesure du métabolisme cérébral au repos a été effectuée en tomographie par émission de positions (18FDG-TEP). Les mesures de corrélation cognitivo-métabolique ont été réalisées au moyen du logiciel SPM8 (p non-corrigé avec hypothèse a priori <0.001). Résultats : Les groupes AD et MCI-C ont un gain moyen moindre que les groupes MCI-S et contrôles. L’ampleur du gain inter-essais est positivement corrélée à l’activité métabolique au niveau de l’hippocampe postérieur chez les patients AD, à l’activité pariétale inférieure chez les patients MCI-S, et à l’activité frontale postérieure dans le groupe contrôle. Par ailleurs, le groupe AD présente plus de pertes inter-essais que les trois autres groupes. Toutefois, aucune corrélation significative n’apparait entre le total des pertes inter-essais et le métabolisme cérébral. Discussion : Ces données suggèrent que les patients AD, même à un stade très précoce (MCI-C) présentent un déficit d’acquisition de l’information. Ce déficit pourrait être sous-tendu par des perturbations métaboliques dans les réseaux d’apprentissage fronto-pariétaux et hippocampique. Il existe de plus un déficit de consolidation inter-essais spécifique aux patients AD mais ce déficit n’est corrélé à aucune région cérébrale au seuil statistique utilisé. [less ▲]

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See detailCombiner les mesures métaboliques cérébrales et neuropsychologiques permet une meilleure prédiction de la conversion vers une maladie d’Alzheimer chez les patients MCI
Bastin, Christine ULg; Adam, Stéphane ULg; LEKEU, Françoise ULg et al

in Revue Neurologique (2009), 165

Introduction. Une voie de recherche neurologique importante concerne la capacité de prédire sur base de l’évaluation initiale des patients avec Mild Cognitive Impairment (MCI) ceux qui vont développer une ... [more ▼]

Introduction. Une voie de recherche neurologique importante concerne la capacité de prédire sur base de l’évaluation initiale des patients avec Mild Cognitive Impairment (MCI) ceux qui vont développer une maladie d’Alzheimer (MA). Parmi les tests neuropsychologiques, le rappel indicé avec indiçage congruent lors de l’encodage et du rappel (RI48) apparaît comme le meilleur prédicteur du devenir des patients MCI (Ivanoiu et al., 2005). D’autre part, on a montré que les mesures métaboliques cérébrales (TEP-FDG), plus particulièrement l’hypométabolisme du cortex temporopariétal, prédit le déclin cognitif global dans le MCI mieux que des mesures neuropsychologiques (Chételat et al., 2005). Le but de notre étude était d’évaluer le pouvoir de prédiction pour la conversion du MCI vers une MA de deux prédicteurs robustes (performance au RI48 et métabolisme cérébral) pris soit isolément soit ensemble. Méthode. 50 patients MCI ont subi un examen en TEP-FDG au repos et ont réalisé le test de rappel indicé RI48 et le MMSE. Au terme d’un suivi neuropsychologique de 36 mois, 28 patients ont évolué vers une MA et 22 sont restés stables. Le métabolisme cérébral et les performances cognitives ont été comparés entre « convertisseurs » et MCI-stables. Des analyses discriminantes ont ensuite permis d’évaluer la capacité de classification de l’âge, du MMSE et des mesures métaboliques et mnésiques considérés individuellement ou selon diverses combinaisons. Résultat. Par comparaison avec les MCI-stables, les « convertisseurs » montraient un hypométabolisme du cortex temporal moyen bilatéralement, du cortex pariétal inférieur droit et du précuneus droit, et de plus faibles performances initiales au RI48. Prises individuellement, les différentes mesures permettaient le même taux de classification correcte (métabolisme cérébral = 76%, RI48 = 76%). L’âge et le MMSE étaient de faibles prédicteurs (exactitude de classification = 62% et 66% respectivement). Par contre, la combinaison des mesures métaboliques et des scores au RI48 prédisaient le mieux la progression vers la MA (88%). Conclusion. Les résultats suggèrent que la stratégie optimale pour identifier quels patients MCI ont plus de risque de développer une MA est de combiner les mesures métaboliques cérébrales et la performance à un test de mémoire très sensible. [less ▲]

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See detailImpaired semantic knowledge underlies the reduced verbal short-term storage capacity in Alzheimer's disease.
Peters, Frederic; Majerus, Steve ULg; De Baerdemaeker, Julie et al

in Neuropsychologia (2009), 47(14), 3067-73

A decrease in verbal short-term memory (STM) capacity is consistently observed in patients with Alzheimer's disease (AD). Although this impairment has been mainly attributed to attentional deficits during ... [more ▼]

A decrease in verbal short-term memory (STM) capacity is consistently observed in patients with Alzheimer's disease (AD). Although this impairment has been mainly attributed to attentional deficits during encoding and maintenance, the progressive deterioration of semantic knowledge in early stages of AD may also be an important determinant of poor STM performance. The aim of this study was to examine the influence of semantic knowledge on verbal short-term memory storage capacity in normal aging and in AD by exploring the impact of word imageability on STM performance. Sixteen patients suffering from mild AD, 16 healthy elderly subjects and 16 young subjects performed an immediate serial recall task using word lists containing high or low imageability words. All participant groups recalled more high imageability words than low imageability words, but the effect of word imageability on verbal STM was greater in AD patients than in both the young and the elderly control groups. More precisely, AD patients showed a marked decrease in STM performance when presented with lists of low imageability words, whereas recall of high imageability words was relatively well preserved. Furthermore, AD patients displayed an abnormal proportion of phonological errors in the low imageability condition. Overall, these results indicate that the support of semantic knowledge on STM performance was impaired for lists of low imageability words in AD patients. More generally, these findings suggest that the deterioration of semantic knowledge is partly responsible for the poor verbal short-term storage capacity observed in AD. [less ▲]

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See detailNeural substrates of phonological and lexicosemantic representations in Alzheimer's disease.
Peters, Frederic; Majerus, Steve ULg; Collette, Fabienne ULg et al

in Human Brain Mapping (2009), 30(1), 185-99

The language profile of patients suffering from Alzheimer's disease (AD) is characterized not only by lexicosemantic impairments but also by phonological deficits, as shown by an increasing number of ... [more ▼]

The language profile of patients suffering from Alzheimer's disease (AD) is characterized not only by lexicosemantic impairments but also by phonological deficits, as shown by an increasing number of neuropsychological studies. This study explored the functional neural correlates underlying phonological and lexicosemantic processing in AD. Using H(215)O PET functional brain imaging, a group of mild to moderate AD patients and a group of age-matched controls were asked to repeat four types of verbal stimuli: words, wordlike nonwords (WL+), non-wordlike nonwords (WL-) and simple vowels. The comparison between the different conditions allowed us to determine brain activation preferentially associated with lexicosemantic or phonological levels of language representations. When repeating words, AD patients showed decreased activity in the left temporo-parietal and inferior frontal regions relative to controls, consistent with distorted lexicosemantic representations. Brain activity was abnormally increased in the right superior temporal area during word repetition, a region more commonly associated with perceptual-phonological processing. During repetition of WL+ and WL- nonwords, AD patients showed decreased activity in the middle part of the superior temporal gyrus, presumably associated with sublexical phonological information; at the same time, AD patients showed larger activation than controls in the inferior temporal gyrus, typically associated with lexicosemantic levels of representation. Overall, the results suggest that AD patients use altered pathways to process phonological and lexicosemantic information, possibly related to a progressive loss of specialization of phonological and lexicosemantic neural networks. [less ▲]

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See detailOn the multivariate nature of brain metabolic impairment in Alzheimer’s disease
Salmon, Eric ULg; Kerrouche, Nacer; Perani, Daniela et al

in Neurobiology of Aging (2009), 30

We used principal component analysis to decompose functional images of patients with AD in orthogonal ensembles of brain regions with maximal metabolic covariance. Three principal components explained 38 ... [more ▼]

We used principal component analysis to decompose functional images of patients with AD in orthogonal ensembles of brain regions with maximal metabolic covariance. Three principal components explained 38% of the total variance in a large sample of FDG-PET images obtained in 225 AD patients. One functional ensemble (PC2) included limbic structures from Papez's circuit (medial temporal regions, posterior and anterior cingulate cortex, thalamus); its disruption in AD patients was related to episodic memory impairment. Another principal component (PC1) illustrated major metabolic variance in posterior cerebral cortices, and patients' scores were correlated to instrumental functions (language and visuospatial abilities). PC3 comprised frontal, parietal, temporal and posteromedial (posterior cingulate and precuneus) cortices, and patients' scores were related to executive dysfunction and global cognitive impairment. The three main metabolic covariance networks converged in the posterior cingulate area that showed complex relationships with medial temporal structures within each PC. Individual AD scores were distributed as a continuum along PC axes: an individual combination of scores would determine specific clinical symptoms in each patient. [less ▲]

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See detailHomeostatic sleep pressure and responses to sustained attention in the suprachiasmatic area.
Schmidt, Christina ULg; Collette, Fabienne ULg; Leclercq, Yves ULg et al

in Science (2009), 324(5926), 516-9

Throughout the day, cognitive performance is under the combined influence of circadian processes and homeostatic sleep pressure. Some people perform best in the morning, whereas others are more alert in ... [more ▼]

Throughout the day, cognitive performance is under the combined influence of circadian processes and homeostatic sleep pressure. Some people perform best in the morning, whereas others are more alert in the evening. These chronotypes provide a unique way to study the effects of sleep-wake regulation on the cerebral mechanisms supporting cognition. Using functional magnetic resonance imaging in extreme chronotypes, we found that maintaining attention in the evening was associated with higher activity in evening than morning chronotypes in a region of the locus coeruleus and in a suprachiasmatic area (SCA) including the circadian master clock. Activity in the SCA decreased with increasing homeostatic sleep pressure. This result shows the direct influence of the homeostatic and circadian interaction on the neural activity underpinning human behavior. [less ▲]

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