Comprendre le stade compensatoire de la maladie d'Alzheimer et agir pour promouvoir la cognition et la plasticité cérébrale

La maladie d’Alzheimer commence par une phase de trouble cognitif léger (TCL), caractérisée par la présence de symptômes mineurs ayant peu ou pas d’impact sur l’autonomie fonctionnelle. L’étude de patients souffrant d’un TCL a permis des avancées spectaculaires dans la compréhension du prodrome de la maladie. Il est ainsi possible d’en dégager le profil cognitif caractéristique : une atteinte de la mémoire épisodique, particulièrement le rappel différé et la mémoire associative, un dysfonctionnement exécutif ou en mémoire de travail et certaines difficultés sémantiques. Les études récentes s’intéressent également aux processus compensatoires qui ont lieu pendant la phase précoce de la maladie. L’imagerie par résonance magnétique fonctionnelle montre en effet que le cerveau est plus actif chez les personnes avec un TCL que chez les individus normaux, une hyperactivation qui a été interprétée par certains comme jouant un rôle compensatoire. Les études d’intervention ont fait appel à des programmes d’entraînement cognitif dans le but de promouvoir l’adaptation et les processus de plasticité compensatoire. Elles ont montré que la mémoire et le bien-être des personnes avec un TCL pouvaient être améliorés par de tels programmes. Elles ont également révélé des changements au niveau de l’activation cérébrale chez les personnes TCL qui recevaient ce type d’intervention. En résumé, les études en neuropsychologie et en neuroscience cognitive ont largement contribué à la caractérisation de cette phase critique de la maladie d’Alzheimer et offrent des avenues d’intervention qui pourraient augmenter l’adaptation et la qualité de vie des personnes atteintes.Alzheimer‘s disease begins with a phase of mild cognitive impairment (MCI), characterized by the presence of minor symptoms that have little or no impact on functional independence. The study of patients with MCI has led to spectacular advances in understanding the prodrome of the disease. It has also produced a typical cognitive profile: an impairment of episodic memory, especially delayed recall and associative memory, deficit in executive functions or working memory and certain semantic problems. Recent studies have also examined compensatory processes that take place during the early phase of the disease. Functional magnetic resonance imagery indicates that the brain is more active in persons with MCI than in normal people. Some researchers have interpreted this hyperactivity as playing a compensatory role. Intervention studies have relied on cognitive training programs to promote adaptation and compensatory plasticity processes. These studies have shown that the memory and well-being of people with MCI could be improved by such programs. They have also revealed changes in the level of cerebral activation among persons with MCI who received this type of intervention. In Summary, studies in neuropsychology and in cognitive neuroscience have greatly contributed to characterizing this critical phase of Alzheimer’s disease and offer avenues for intervention that could increase adaptation and improve the quality of life of people suffering from the disease

Relationships between years of education, regional grey matter volumes, and working memoryrelated brain activity in healthy older adults

The aim of this study was to examine the relationships between educational attainment, regional grey matter volume, and functional working memory-related brain activation in older adults. The final sample included 32 healthy older adults with 8 to 22 years of education. Structural magnetic resonance imaging (MRI) was used to measure regional volume and functional MRI was used to measure activation associated with performing an n-back task. A positive correlation was found between years of education and cortical grey matter volume in the right medial and middle frontal gyri, in the middle and posterior cingulate gyri, and in the right inferior parietal lobule. The education by age interaction was significant for cortical grey matter volume in the left middle frontal gyrus and in the right medial cingulate gyrus. In this region, the volume loss related to age was larger in the low than high-education group. The education by age interaction was also significant for task-related activity in the left superior, middle and medial gyri due to the fact that activation increased with age in those with higher education. No correlation was found between regions that are structurally related with education and those that are functionally related with education and age. The data suggest a protective effect of education on cortical volume. Furthermore, the brain regions involved in the working memory network are getting more activated with age in those with higher educational attainment

Single and Multiple Domain Amnestic MCI: two sides of the same coin?

Background. Amnestic Mild Cognitive Impairment (aMCI) is considered a transition stage between normal aging and Alzheimer's disease (AD). Two main clinical subtypes of aMCI have been identified: 1) aMCI single domain (aMCI-SD), with isolated episodic memory impairments, and 2) aMCI multiple domain (aMCI-MD), with episodic memory impairments and deficits in one or more other cognitive domains. Aims.To map the pattern of gray matter (GM) atrophy associated with aMCI-SD, aMCIMD and mild AD. Methods. A group of aMCI-SD, aMCI-MD characterized by executive function disorders, mild AD patients and cognitively unimpaired age-matched subjects underwent a comprehensive neuropsychological assessment and a high-definition MR brain scan. Voxel-based morphometry (VBM) analysis was used to characterize the GM tissue loss in each patient group, and the common pattern of GM atrophy in aMCI-SD and aMCIMD. Results. The results revealed that aMCI-SD and aMCI-MD are characterized by a common pattern of GM atrophy within the medial temporal cortex, predisposing to AD and correlating with the severity of verbal memory symptoms. Moreover, the pattern of GM atrophy observed in aMCI-SD, aMCI-MD and mild AD revealed that, from an anatomical point of view, these three clinical syndromes could represent three severity points along the continuum between normal aging and AD

Trouble léger de la cognition : profils variés en compréhension de texte = Mild cognitive impairment: varied texts comprehension profiles

La compréhension de textes est une composante complexe qui requiert à la fois des compétences linguistiques et cognitives. Aussi, l’apparition d’un trouble léger de la cognition (TLC) est susceptible de générer des difficultés en compréhension de textes. Toutefois, l’hétérogénéité du profil cognitif de ces personnes suggère un profil de compréhension en lecture tout aussi hétérogène. L’objectif de cette étude est, d’une part, d’identifier, chez des participants avec TLC, les atteintes de la compréhension de textes en fonction de la demande cognitive des textes et, d’autre part, d’étudier les liens présents entre la compréhension de textes et leur profil cognitif. Méthodologie : Vingt participants avec TLC ont été inclus dans l’étude. Leur profil cognitif a été établi à l’aide de différents tests neuropsychologiques. Leur compréhension de textes a été évaluée à l’aide d’un test de compréhension de textes, le « T.C.T. », constitué de trois textes dont la charge sémantique varie et de trois questionnaires. Une analyse descriptive et qualitative des résultats a été faite ainsi qu’une analyse de corrélation entre les résultats aux tests neuropsychologiques et les résultats au T.C.T. Résultats : Une atteinte de la compréhension (détails et idées principales) dépendante de la charge sémantique a été retrouvée chez 12 participants. Des corrélations significatives ont été observées entre le rappel des idées principales et des détails de deux textes sur trois et la mémoire épisodique. Conclusion : Les résultats de cette étude permettent d’appréhender la variabilité des profils en compréhension de textes engendrée par un TLC et donc de mieux cibler les interventions possibles en orthophonie. Text comprehension is a complex component that requires both linguistic and cognitive abilities. Mild cognitive impairment (MCI) may cause difficulties in text comprehension. However, the heterogeneity of these individuals’ cognitive profiles also suggests heterogeneous reading comprehension profiles. The purpose of this study was, first, to identify the text comprehension impairments associated to the cognitive load of texts in participants with MCI, and second, to study the links between reading comprehension and cognitive profiles. Methods: Twenty participants with MCI were included in the study. The cognitive profile was assessed using various neuropsychological tests. Text comprehension was evaluated with the reading comprehension test, “ T.C.T.”, that included three texts with varied semantic load, and three questionnaires. A descriptive and qualitative analysis of the results was done, as well as a correlation analysis between the results of the neurosphychological tests and the T.C.T. test. Results: Text comprehension impairments (details and main ideas) were found to be dependant upon the semantic load in 12 participants. Significant correlations were observed between episodic memory and the recall of the main ideas and details in two of the three texts. Conclusion: The results of this study make it possible to understand the variability of text comprehension profiles in individuals with MCI. This may allow better-targeted speech-language interventions

The SPECTRA Study: Validating a New Memory Training Program based on the Episodic Specificity Induction to Promote Transfer in Older Adults

Some complex cognitive activities impacted by aging (future thinking, problem-solving, creative thinking) have been shown to rely on episodic retrieval, suggesting that cognitive interventions aiming to improve retrieval have the potential to induce transfer effects to these activities. Prior studies have shown that a brief one-session technique called Episodic Specificity Induction (ESI) can transiently improve episodic retrieval and induce transfer effects to complex tasks that rely on episodic retrieval in older adults. In the present proof-of-concept study, we assessed whether a training program consisting of repeated practice of the ESI technique can improve episodic retrieval and transfer to complex tasks. Fifteen healthy older adults completed a six-session intervention where they received repeated ESI practice. Before and after the intervention, nearest transfer effects were assessed using free recall, near transfer effects using recognition and associative recognition, and far-transfer effects using mean-ends problem-solving and divergent creative thinking. Before the intervention, typical ESI effects were observed (better performance after an ESI than after a control task), indicating that the ESI operated as expected in our sample. When examining the intervention effects, performance was increased after the intervention on free recall and recognition (nearest- and near-transfer) as well as problem-solving and divergent creative thinking (far transfer). These results indicate that an intervention relying on the ESI technique can produce both near and far transfer. These findings support the use of the ESI in the design of interventions that could improve retrieval and have a broad impact on a range of complex tasks

The Relation Between Depressive Symptoms and Semantic Memory in Amnestic Mild Cognitive Impairment and in Late-Life Depression

Semantic deficits have been documented in the prodromal phase of Alzheimer’s disease, but it is unclear whether these deficits are associated with non-cognitive manifestations. For instance, recent evidence indicates that cognitive deficits in elders with amnestic mild cognitive impairment (aMCI) are modulated by concomitant depressive symptoms. The purposes of this study were to (i) investigate if semantic memory impairment in aMCI is modulated according to the presence (aMCI-D group) or absence (aMCI group) of depressive symptoms, and (ii) compare semantic memory performance of aMCI and aMCI-D groups to that of patients with late-life depression (LLD). Seventeen aMCI, 16 aMCI-D, 15 LLD, and 26 healthy control participants were administered a semantic questionnaire assessing famous person knowledge. Results showed that performance of aMCI-D patients was impaired compared to the control and LLD groups. However, in the aMCI group performance was comparable to that of all other groups. Overall, these findings suggest that semantic deficits in aMCI are somewhat associated with the presence of concomitant depressive symptoms. However, depression alone cannot account solely for the semantic deficits since LLD patients showed no semantic memory impairment in this study. Future studies should aim at clarifying the association between depression and semantic deficits in older adults meeting aMCI criteria.Instituts de recherche en santé du Canada (IRSC) IAO-8467

Putting music to trial : Consensus on key methodological challenges investigating music-based rehabilitation

Publisher Copyright: © 2022 The Authors. Annals of the New York Academy of Sciences published by Wiley Periodicals LLC on behalf of New York Academy of Sciences.Major advances in music neuroscience have fueled a growing interest in music-based neurological rehabilitation among researchers and clinicians. Musical activities are excellently suited to be adapted for clinical practice because of their multisensory nature, their demands on cognitive, language, and motor functions, and music's ability to induce emotions and regulate mood. However, the overall quality of music-based rehabilitation research remains low to moderate for most populations and outcomes. In this consensus article, expert panelists who participated in the Neuroscience and Music VII conference in June 2021 address methodological challenges relevant to music-based rehabilitation research. The article aims to provide guidance on challenges related to treatment, outcomes, research designs, and implementation in music-based rehabilitation research. The article addresses how to define music-based rehabilitation, select appropriate control interventions and outcomes, incorporate technology, and consider individual differences, among other challenges. The article highlights the value of the framework for the development and evaluation of complex interventions for music-based rehabilitation research and the need for stronger methodological rigor to allow the widespread implementation of music-based rehabilitation into regular clinical practice.Peer reviewe

Evidence of a relation between hippocampal volume, white matter hyperintensities, and cognition in subjective cognitive decline and mild cognitive impairment

Objective: The concepts of mild cognitive impairment (MCI) and subjective cognitive decline (SCD) have been proposed to identify individuals in the early stages of Alzheimer’s disease (AD), or other neurodegenerative diseases. One approach to validate these concepts is to investigate the relationship between pathological brain markers and cognition in those individuals. Method: We included 126 participants from the Consortium for the Early Identification of Alzheimer’s disease-Quebec (CIMA-Q) cohort (67 SCD, 29 MCI, and 30 cognitively healthy controls [CH]). All participants underwent a complete cognitive assessment and structural magnetic resonance imaging. Group comparisons were done using cognitive data, and then correlated with hippocampal volumes and white matter hyperintensities (WMHs). Results: Significant differences were found between participants with MCI and CH on episodic and executive tasks, but no differences were found when comparing SCD and CH. Scores on episodic memory tests correlated with hippocampal volumes in both MCI and SCD, whereas performance on executive tests correlated with WMH in all of our groups. Discussion: As expected, the SCD group was shown to be cognitively healthy on tasks where MCI participants showed impairment. However, SCD’s hippocampal volume related to episodic memory performances, and WMH to executive functions. Thus, SCD represents a valid research concept and should be used, alongside MCI, to better understand the preclinical/prodromal phase of AD