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See detailMetabolic and structural connectivity within the default mode network relates to working memory performance in young healthy adults
Yakushev, Igor; Chételat, Gael; Fischer F.U. et al

in NeuroImage (2013), 79

Studies of functional connectivity suggest that the default mode network (DMN) might be relevant for cognitive functions. Here, we examined metabolic and structural connectivity between major DMN nodes ... [more ▼]

Studies of functional connectivity suggest that the default mode network (DMN) might be relevant for cognitive functions. Here, we examined metabolic and structural connectivity between major DMN nodes, the posterior cingulate (PCC) and medial prefrontal cortex (MPFC), in relation to normal working memory (WM). DMN was captured using independent component analysis of [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) data from 35 young healthy adults (27.1±5.1 years). Metabolic connectivity, a correlation between FDG uptake in PCC and MPFC, was examined in groups of subjects with (relative to median) low (n=18) and high (n=17) performance on digit span backward test as an index of verbal WM. In addition, fiber tractography based on PCC and MPFC nodes as way points was performed in a subset of subjects. FDG uptake in the DMN nodes did not differ between high and low performers. However, significantly (p=0.01) lower metabolic connectivity was found in the group of low performers. Furthermore, as compared to high performers, low performers showed lower density of the left superior cingulate bundle. Verbal WM performance is related to metabolic and structural connectivity within the DMN in young healthy adults. Metabolic connectivity as quantified with FDG-PET might be a sensitive marker of the normal variability in some cognitive functions. [less ▲]

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See detailRelationships between brain metabolism decrease in normal aging and changes in structural and functional connectivity
Chételat, Gael; Landeau, Brigitte; Salmon, Eric ULg et al

in NeuroImage (2013), 76

Normal aging is characterized by brain glucose metabolism decline predominantly in the prefrontal cortex. The goal of the present study was to assess whether this change was associated with age-related ... [more ▼]

Normal aging is characterized by brain glucose metabolism decline predominantly in the prefrontal cortex. The goal of the present study was to assess whether this change was associated with age-related alteration of white matter (WM) structural integrity and/or functional connectivity. FDG-PET data from 40 young and 57 elderly healthy participants from two research centres (n=49/48 in Centre 1/2) were analyzed. WM volume from T1-weighted MRI (Centre 1), fractional anisotropy from diffusion-tensor imaging (Centre 2), and resting-state fMRI data (Centre 1) were also obtained. Group comparisons were performed within each imaging modality. Then, positive correlations were assessed, within the elderly, between metabolism in the most affected region and the other neuroimaging modalities. Metabolism decline in the elderly predominated in the left inferior frontal junction (LIFJ). LIFJ hypometabolism was significantly associated with macrostructural and microstructural WM disturbances in long association fronto-temporo-occipital fibers, while no relationship was found with functional connectivity. The findings offer new perspectives to understand normal aging processes and open avenues for future studies to explore causality between age-related metabolism and connectivity changes. [less ▲]

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See detailImpairments of 3D visual perception in posterior cortical atrophy: functional and anatomical characterization
Gillebert, Céline; Bastin, Christine ULg; Sunaert, Stefan et al

Conference (2013)

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See detailEpisodic autobiographical memory in amnestic Mild Cognitive Impairment: What are the neural correlates?
Bastin, Christine ULg; Feyers, Dorothée ULg; Jedidi, Haroun ULg et al

in Human Brain Mapping (2013), 34

Autobiographical memory in amnestic Mild Cognitive Impairment (aMCI) is characterized by impaired retrieval of episodic memories, but relatively preserved personal semantic knowledge. This study aimed to ... [more ▼]

Autobiographical memory in amnestic Mild Cognitive Impairment (aMCI) is characterized by impaired retrieval of episodic memories, but relatively preserved personal semantic knowledge. This study aimed to identify (via FDG-PET) the neural substrates of impaired episodic specificity of autobiographical memories in 35 aMCI patients compared with 24 healthy elderly controls. Significant correlations between regional cerebral activity and the proportion of episodic details in autobiographical memories from two life periods were found in specific regions of an autobiographical brain network. In aMCI patients, more than in controls, specifically episodic memories from early adulthood were associated with metabolic activity in the cuneus and in parietal regions. We hypothesized that variable retrieval of episodic autobiographical memories in our aMCI patients would be related to their variable capacity to reactivate specific sensory-perceptual and contextual details of early adulthood events linked to reduced (occipito-parietal) visual imagery and less efficient (parietal) attentional processes. For recent memories (last year), a correlation emerged between the proportion of episodic details and activity in lateral temporal regions and the temporo-parietal junction. Accordingly, variable episodic memory for recent events may be related to the efficiency of controlled search through general events likely to provide cues for the retrieval of episodic details and to the ability to establish a self perspective favouring recollection. [less ▲]

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See detailItem familiarity and controlled associative retrieval in Alzheimer's disease: An fMRI study
Genon, Sarah ULg; Collette, Fabienne ULg; Feyers, Dorothée ULg et al

in Cortex : A Journal Devoted to the Study of the Nervous System & Behavior (2013), 49

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See detailFonctionnement mnésique et maladie d’Alzheimer
Salmon, Eric ULg; Bastin, Christine ULg

in Lettre des Académies (La) (2013), 29

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See detailThe neural correlates of recollection and familiarity during aging
Angel, Lucie; Bastin, Christine ULg; Genon, Sarah ULg et al

in Journal of Psychophysiology (2013), 27(Suppl 1), 48

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See detailThe neural correlates of recollection and familiarity during aging
Angel, Lucie; Bastin, Christine ULg; Genon, Sarah ULg et al

Poster (2013)

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See detailAssociative memory in aging: The effect of unitization on source memory
Bastin, Christine ULg; Diana, Rachel A.; Simon, Jessica ULg et al

in Psychology & Aging (2013), 28(1), 275-283

In normal aging, memory for associations declines more than memory for individual items. Unitization is an encoding process defined by creation of a new single entity to represent a new arbitrary ... [more ▼]

In normal aging, memory for associations declines more than memory for individual items. Unitization is an encoding process defined by creation of a new single entity to represent a new arbitrary association. The current study tested the hypothesis that age-related differences in associative memory can be reduced following encoding instructions that promote unitization. In two experiments, groups of 20 young and 20 older participants learned new associations between a word and a background color under two conditions. In the item detail condition, they had to imagine that the item is the same color as the background; an instruction promoting unitization of the associations. In the context detail condition, that did not promote unitization, they had to imagine that the item interacted with another colored object. At test, they had to retrieve the color that was associated to each word (source memory). In both experiments, the results showed an age-related decrement in source memory performance in the context detail but not in the item detail condition. Moreover, Experiment 2 examined receiver operating characteristics in older participants and indicated that familiarity contributed more to source memory performance in the item detail than in the context detail condition. These findings suggest that unitization of new associations can overcome the associative memory deficit observed in aging, at least for item-color associations. [less ▲]

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See detailCONTROLLED AND AUTOMATIC MEMORY RETRIEVAL IN ALZHEIMER’S DISEASE
Bastin, Christine ULg; Genon, Sarah ULg; Willems, Sylvie ULg et al

in Proceedings of the 8th Panhellenic Interdisciplinary Conference of Alzheimer's Disease and Related Disorders (2013)

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See detailEnhancing the salience of fluency improves recognition memory performance in mild Alzheimer’s disease
Bastin, Christine ULg; Willems, Sylvie ULg; Genon, Sarah ULg et al

in Journal of Alzheimer's Disease [=JAD] (2013), 33

Recognition memory can rely on recollection (recall of the details from the encoding episode) and familiarity (feeling that some information is old without any recollection). In Alzheimer’s disease (AD ... [more ▼]

Recognition memory can rely on recollection (recall of the details from the encoding episode) and familiarity (feeling that some information is old without any recollection). In Alzheimer’s disease (AD), whereas there is a clear deficit of recollection, the evidence regarding familiarity is mixed, with some studies showing preserved familiarity and others reporting impairment. The current study examined whether recognition memory performance can be improved in AD when the use of familiarity is facilitated by the salience of processing fluency due to an earlier encounter with the information. Fifteen AD patients and 16 healthy controls performed a verbal recognition memory task where the salience of fluency was manipulated by means of letters overlap. Studied and unstudied words were constituted of either two separate sets of letters (no-overlap condition, high fluency salience) or the same set of letters (overlap condition, low fluency salience). The results showed that, although performance was globally poorer in AD patients than in the controls, both groups performed significantly better in the no-overlap condition than in the overlap condition. This suggests that AD patients benefited as much as the controls from the salience of fluency. [less ▲]

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See detailVerbal learning in Alzheimer’s disease and mild cognitive impairment:fine-grained acquisition and short-delay consolidation performance and neural correlates
Genon, Sarah ULg; Collette, Fabienne ULg; Moulin, Chris et al

in Neurobiology of Aging (2013), 34

The aim of this study was to examine correlations between acquisition and short-delay consolidation and brain metabolism at rest measured by fluorodeoxyglucose positron emission tomography (FDG-PET) in 44 ... [more ▼]

The aim of this study was to examine correlations between acquisition and short-delay consolidation and brain metabolism at rest measured by fluorodeoxyglucose positron emission tomography (FDG-PET) in 44 Alzheimer’s disease (AD) patients, 16 patients with mild cognitive impairment (MCI) who progressed to dementia (MCI-AD), 15 MCI patients who remained stable (MCI-S, 4–8 years of follow-up), and 20 healthy older participants. Acquisition and short-delay consolidation were calculated respectively as mean gained (MG) and lost (ML) access to items of the California Verbal Learning Task. MG performance suggests that acquisition is impaired in AD patients even at predementia stage (MCI-AD). ML performance suggests that short-delay consolidation is deficient only in confirmed AD patients. Variations in acquisition performance in control participants are related to metabolic activity in the anterior parietal cortex, an area supporting task-positive attentional processes. In contrast, the acquisition deficit is related to decreased activity in the lateral temporal cortex, an area supporting semantic processes, in patients at an early stage of AD and is related to metabolic activity in the hippocampus, an area supporting associative processes, in confirmed AD patients. [less ▲]

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See detailItem familiarity and controlled associative retrieval in Alzheimer’s disease: an fMRI study.
Genon, Sarah ULg; Collette, Fabienne ULg; Feyers, Dorothée ULg et al

in Proceedings of the Amsterdam Memory Slam 2012 (2012, August 30)

Alzheimer’s disease (AD) is characterised by altered recollection function, with impaired controlled retrieval of associations. In contrast, familiarity-based memory for individual items may sometimes be ... [more ▼]

Alzheimer’s disease (AD) is characterised by altered recollection function, with impaired controlled retrieval of associations. In contrast, familiarity-based memory for individual items may sometimes be preserved in early stages of the disease. This is the first study that directly examines whole brain regional activity engaged during one core aspect of the recollection function: associative controlled episodic retrieval (CER), contrasted to item familiarity in AD patients. Cerebral activity related to associative CER and item familiarity in AD patients and healthy controls (HC) was measured with functional magnetic resonance imaging during a word-pair recognition task to which the process dissociation procedure was applied. Some patients had null CER estimates (AD-), whereas others did show some CER abilities (AD+) although significantly less than HC. In contrast, familiarity estimates were equivalent in the three groups. In AD+ like in controls, associative CER activated the inferior precuneus/posterior cingulate cortex (PCC). However, during associative CER, functional connection between this region and the hippocampus, the inferior parietal and the dorsolateral prefrontal cortex was significantly higher in HC than in AD+. In the three groups, item familiarity was related to activation along the intraparietal sulcus (IPS). In conclusion, whereas the preserved automatic detection of an old item (without retrieval of accurate word association) is related to a parietal activation centred on the IPS, the inferior precuneus/PCC supports associative CER ability in AD patients as in HC. However, AD patients have deficient functional connectivity during associative CER suggesting that residual recollection function in these patients might be impoverished by lack of some recollection-related aspects such as autonoetic quality, episodic details and verification. [less ▲]

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See detailMétamémoire pour des informations épisodiques et sémantiques dans la maladie d’Alzheimer.
Simon, Jessica ULg; Bastin, Christine ULg; Collette, Fabienne ULg et al

in Proceedings of the "XIIème Colloque International sur le Vieillissement Cognitif" (2012, June 25)

Quelques études ont examiné la précision du jugement concernant leur propre mémoire chez des patients présentant une maladie d’Alzheimer (MA) à l’aide de la procédure « Feeling-of-Knowing » (FOK). Dans ... [more ▼]

Quelques études ont examiné la précision du jugement concernant leur propre mémoire chez des patients présentant une maladie d’Alzheimer (MA) à l’aide de la procédure « Feeling-of-Knowing » (FOK). Dans cette procédure, le participant est invité à prédire sa capacité à reconnaître parmi des distracteurs l’item qu’il n’est pas parvenu à rappeler avant de passer à la phase de reconnaissance. Chez les patients en début de MA, la précision du jugement semble préservée lorsque la tâche implique la mémoire sémantique mais apparaît altérée lorsque la tâche implique la mémoire épisodique (Perrotin & Insingrini, 2010). Il existerait donc une dissociation dans la précision du jugement métacognitif chez les patients avec MA débutante entre les domaines épisodique et sémantique. Cependant, cette hypothèse n’a jamais été examinée au sein d’une même tâche. Dans cette étude, nous avons administré une version adaptée du FOK à 23 patients avec MA débutante et 17 sujets de contrôle. Les participants voyaient des visages de personnes dont ils avaient dû étudier le nom auparavant (items épisodiques) et des visages de personnes célèbres (items sémantiques). Pour chaque visage, les participants devaient indiquer la probabilité qu’ils reconnaissent le nom de la personne sur une échelle qualitative à 4 points (« Aucune chance », « Faible chance », « Forte chance », « Je le connais (rappel) ») puis reconnaître le nom parmi 3 distracteurs. La précision des jugements a été évaluée à l’aide du score de Hamann. Une ANOVA a révélé un effet significatif d’interaction entre le groupe et le domaine mnésique (P = .05), la moindre précision du jugement en mémoire épisodique étant exacerbée chez les patients avec MA. Cette étude renforce donc l’hypothèse selon laquelle il existe une dissociation entre les domaines épisodique et sémantique dans la capacité métacognitive des patients avec MA débutante. Perrotin, A. & Insingrini, M. (2010). La métamémoire et sa fonction de monitoring dans le vieillissement normal et dans la maladie d’Alzheimer. Revue de Neurospsychologie Neurosciences cognitives et cliniques, 2(4), 299-309. [less ▲]

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See detailSelf-appraisal and medial prefrontal activation in early stage Alzheimer’s disease
Genon, Sarah ULg; Collette, Fabienne ULg; Angel, Lucie et al

Poster (2012, June 12)

Introduction Self-referential processing in healthy subjects is related to activation within cortical midline structures, such as the medial prefrontal cortex (MPFC) and the posterior cingulate cortex ... [more ▼]

Introduction Self-referential processing in healthy subjects is related to activation within cortical midline structures, such as the medial prefrontal cortex (MPFC) and the posterior cingulate cortex (PCC; Northoff et al., 2006). Little is know about the engagement of these structures during self-referential processing at different stages of Alzheimer’s disease (AD). The PCC and the MPFC have been found to be activated during a self-appraisal task of adjectives in patients at very early stage of the disease (patients with Mild Cognitive Impairment, MCI; Ries et al., 2006). In contrast, in a similar task, Ruby et al. (2009) have found that mild demented patients activated the dorsal part of the MPFC (DMPFC) to a lesser extent than healthy controls (HC). Ruby et al. did not assess depression symptoms in their patients. Yet, MPFC activations have been found to be modified during self-referential processing in depressed participants (Lemogne et al., 2012). Therefore, in this study, we examined brain correlates of self-appraisal processing in AD patients when controlling for depressive symptoms. Methods Twenty-two mild AD patients and 22 HC matched on age, level of education and gender (respectively: 76±5y; 11±3y; 12M10F) to the AD patients (respectively: 76±7y; 11±3y; 11M11F) were recruited. To control for dementia severity and depression, the participants were administrated the Mattis Dementia Rating (MDR) and the Geriatric Depression Scale (GDS). A self-appraisal task intermixed with a recognition task was administered in an fMRI experimentation. In the self-appraisal task, the participants saw adjectives and had to indicate if the trait describes them (Self-condition; SC) or the King Albert II (for men)/the Queen Fabiola (for women; Other-condition; OC). The adjectives were presented in blocks of 6 items. Participants performed 9 runs consisting in one block of SC and one block of OC followed by a recognition phase where participants were presented with the 12 adjectives that they had just previously seen randomly mixed with 12 new adjectives. They were asked to indicate for each adjective whether they had seen it in the previous task. Statistical analyses focused on the self-appraisal task. Brain activations related to the self appraisal process were isolated in each participant by subtracting brain activation related to OC items from brain activation related to SC items. Then at the group level, we examined differences between groups (HC>AD and AD>HC) and a conjunction analysis examined brain activations that were common to both groups. Preprocessing and statistical analyses were performed with SPM8 (p<.001 uncorrected with a-priori hypotheses). Results GDS scores were similar in AD (3±3) and HC (3±3; T(42) = .1; P=.9) groups. No region was found to be significantly more activated during self-appraisal process in HC than in AD and vice versa when performing direct statistical comparison. Moreover, a conjunction analysis revealed that the VMPFC was the only region commonly activated in AD and HC during self-appraisal process (Punc<.001). Conclusions Our results revealed that AD patients engaged the ventral part of the MPFC to a similar extent than HC during self-appraisal judgements. These results and the results found in patients with MCI by Ries et al. (2006) suggest that at initial stages of AD, patients engaged self-related regions when they performed judgements about themselves as HC do. The divergence with the findings by Ruby et al. (2009) may be related either to the fact that they did not controlled for depressive symptoms or to the fact that their patients showed on average lower scores at the MDR (124) than our patients (127). One can assume that engagement of the self-related regions during self-appraisal judgements in the AD patients depends on the severity of the dementia and/or depressive symptoms. In conclusion, MPFC may be engaged during self-referential processing in very mild AD patients without depressive symptoms. References: Lemogne, C., Delaveau, P., Freton, M., Guionnet, S. & Fossati, P. (2012). Medial prefrontal cortex and the self in major depression. Journal of Affective Disorders, 136, 1-11. Ries, M. L., Schmitz, T.W., Kawahara, T.N., Torgerson, B.M., Trivedi, M.A. & Johnson, S.C. (2006). Task-dependent posterior cingulated activation in mild cognitive impairment. NeuroImage, 29, 485-492. Ruby, P., Collette, F., D’Argembeau, A., Péters, F., Degueldre, C., Balteau, E., Luxen, A., Maquet, P. & Salmon, E. (2009). Perspective taking to assess self-personality: What’s modified in Alzheimer’s disease ? Neurobiology of Aging, 30(10), 1637-1651. [less ▲]

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