Registered report: Age-preserved semantic memory and the CRUNCH effect manifested as differential semantic control networks: An fMRI study.

Semantic memory representations are generally well maintained in aging, whereas semantic control is thought to be more affected. To explain this phenomenon, this study tested the predictions of the Compensation-Related Utilization of Neural Circuits Hypothesis (CRUNCH), focusing on task demands in aging as a possible framework. The CRUNCH effect would manifest itself in semantic tasks through a compensatory increase in neural activation in semantic control network regions but only up to a certain threshold of task demands. This study compares 39 younger (20-35 years old) with 39 older participants (60-75 years old) in a triad-based semantic judgment task performed in an fMRI scanner while manipulating task demand levels (low versus high) through semantic distance. In line with the CRUNCH predictions, differences in neurofunctional activation and behavioral performance (accuracy and response times) were expected in younger versus older participants in the low- versus high-demand conditions, which should be manifested in semantic control Regions of Interest (ROIs). Our older participants had intact behavioral performance, as proposed in the literature for semantic memory tasks (maintained accuracy and slower response times (RTs)). Age-invariant behavioral performance in the older group compared to the younger one is necessary to test the CRUNCH predictions. The older adults were also characterized by high cognitive reserve, as our neuropsychological tests showed. Our behavioral results confirmed that our task successfully manipulated task demands: error rates, RTs and perceived difficulty increased with increasing task demands in both age groups. We did not find an interaction between age group and task demand, or a statistically significant difference in activation between the low- and high-demand conditions for either RTs or accuracy. As for brain activation, we did not find the expected age group by task demand interaction, or a significant main effect of task demand. Overall, our results are compatible with some neural activation in the semantic network and the semantic control network, largely in frontotemporoparietal regions. ROI analyses demonstrated significant effects (but no interactions) of task demand in the left and right inferior frontal gyrus, the left posterior middle temporal gyrus, the posterior inferior temporal gyrus and the prefrontal gyrus. Overall, our test did not confirm the CRUNCH predictions.

Brief instrument for direct complex functionality assessment: a new ecological tool.

Background: The Direct Assessment of Functional Status (DAFS) is the only instrument validated in Brazil that assesses functionality directly with the patient. However, this clinical tool takes a long time to be administered. This limits its use in hospitals and outpatient clinics that require brief assessment instruments. Additionally, we need to count with a direct assessment because the number of older adults living alone is increasing and we thus lack reliable informants. Objective: This study aimed to present the development and content validity evidence of a direct complex functionality test for older adults, the Brief Instrument for Direct Functionality Assessment (BIDFA). Method: A total sample of 30 older adults and eight expert judges took part in the study stages. The BIDFA construction stages were: (1) literature review of functionality instruments; (2) development of seven ecological tasks to evaluate the performance of daily complex activities with the older adults; (3) content analysis by eight expert judges; (4) pilot study with 30 older adults; (5) the ecological analysis of items; (6) focus group analysis; and (7) final version of the BIDFA. Results: The BIDFA had evidence of content validity with an agreement index of 96.5%. The final version of BIDFA was left with six domains of complex functionality divided into semantic memory and time orientation; shopping skills; executive attention, math and finance skills; organization; planning and procedural memory; and problem-solving. The complex functionality score by BIDFA ranges from 0 to 100 points. Conclusion: The BIDFA was found to have good content validity by the expert judges and by the ecological analysis of the items by the older adults. The new instrument is expected to help assess the functional status of older adults, in an abbreviated context including complex functionality demands, with a wider range of total and subdomain scores.

Automatic assessment of connected speech and its relation to memory in Alzheimer's Disease in low education.

INTRODUCTION: Discourse is one of the main linguistic aspects affected by Alzheimer's Disease (AD) and its relationship with memory needs to be further studied, mainly in low education and low socioeconomic status (SES) groups. The present study aimed at investigating differences in the recall of short narratives between participants with mild AD (AD) and a control group of typical older adults (CG) with the use of automatic assessment. METHODS: 17 older adults diagnosed with AD (mean age 76.41, mean education 5,82) and 34 typical older adults (mean age 74.26, mean education 7.09) were asked to listen to and then retell a short story. Syntactic, lexical, and semantic features were assessed via the NILC-Metrix software, and the features were correlated with episodic, working, and semantic memory assessment. RESULTS: Differences were found in 7 of the 34 features assessed. Syntactically, the group diagnosed with AD produced narratives with fewer sentences, fewer words per sentence, and lower Yngve depth scores. Lexically, the AD group produced narratives with fewer words and prepositions per sentence. Semantically, the narratives produced by the AD group featured words with a lower mean age of acquisition, and lower Brunét's index scores. For the CG group, episodic memory performance correlated with the ratio of conjunctions. No other significant correlation was found for semantic and working memory in the CG. No correlation was found between memory performance and linguistic features for the AD group. DISCUSSION: The automatic assessment of linguistic features showed impaired narrative recall in participants diagnosed with AD relative to healthy controls at the syntactic, lexical, and semantic levels of discourse. These findings corroborate previous literature showing a decline in discourse production performance resulting from cognitive impairment in AD. CONCLUSION: The assessment of linguistic performance through a narrative recall task provides valuable insights into cognitive decline related to Alzheimer's disease.

T-DAV: Action naming test with videos. Development, validation and standardization / T-DAV : Test de dénomination d'actions par visionnement de vidéos. Développement, validation et normalisation

Word finding difficulties, particularly for verbs, are a common symptom in post-stroke aphasia and people with neurodegenerative diseases, such as Alzheimer's disease. Word finding difficulties for verbs are mainly assessed by action naming tasks, using often images depicting actions. However, videos seem to be more adapted than images for action naming. To date, there are no action naming tests using videos available in French. The aim of this study is to present the T-DAV, an action naming test with videos, and its psychometric properties (validity and reliability). The T-DAV is composed of 20 videos (10 high frequency and 10 low frequency actions). High and low frequency stimuli are matched for several relevant psycholinguistic variables (e.g., length in phonemes). Performance on the T-DAV is associated with performance on the DVL-38 test, a French action naming test using images (concurrent validity). The T-DAV allows to differentiate the performance of healthy individuals from that of Alzheimer's Disease patients (discriminant validity). The items of the T-DAV show good internal consistency (reliability). In sum, the T-DAV shows good pshychometric properties and counts with norms for French-speaking adults. The T-DAV fulfills a clinical need of action naming tests with videos in French.

Le manque du verbe est un symptôme clinique présent chez les patients aphasiques post-accident vasculaire cérébral et atteints de maladies neurodégénératives comme la maladie d'Alzheimer (MA). L'évaluation du manque du verbe se fait souvent avec des tâches de dénomination d'actions portant sur des images. Or, le support vidéo semble être plus adapté que les images pour la dénomination d'actions. À ce jour, aucun test français n'évalue la dénomination d'actions par vidéos. L'objectif de cet article est de présenter le Test de dénomination d'actions par vidéos (T-DAV) et l'étude de ses propriétés psychométriques (validité et fiabilité). Le T-DAV est composé de 20 vidéos (10 actions de haute fréquence et 10 de basse fréquence), appariées par plusieurs variables psycholinguistiques. La performance au T-DAV est associée à celle du test DVL-38 pour la dénomination d'actions avec images (validité concurrente). Les scores au T-DAV permettent de différencier la performance des personnes saines et celles atteintes de la MA (validité discriminante). Les items du T-DAV montrent une bonne consistance interne (fiabilité). En somme, le T-DAV montre de très bonnes propriétés psychométriques et présente des normes pour une population francophone adulte. Le T-DAV comble ainsi le manque de tests francophones de dénominations d'actions par vidéos.

Reading and writing habits compensate for aging effects in speech connectedness.

We investigate the association of short- and long-range recurrences (speech connectedness) with age, education, and reading and writing habits (RWH) in typical aging using an oral narrative production task. Oral narrative transcriptions were represented as word-graphs to measure short- and long-range recurrences. Speech connectedness was explained by the combination of age, education, and RWH, and the strength of RWH's coefficient reflects the aging effect.

Normative Data for Healthy French-Speaking Persons Aged 80 Years and Older for the DTLA Language Screening Test.

The Detection Test for Language Impairments in Adults and the Aged (DTLA) is a quick, sensitive, and standardized screening test designed to assess language disorders in adults and elderly people. The test was specifically developed to detect linguistic impairment associated with major neurocognitive disorders. In 2017, we established normative data on 545 healthy individuals between 50 and 80 years old from four French-speaking countries: Belgium, Canada (Quebec), France, and Switzerland. OBJECTIVE: The objective of the present study was to develop norms for the population older than 80 years of age for the DTLA. METHOD: We extend the original normative data to include 149 healthy, community-dwelling, French-speaking adults aged 80 years old and older from the same countries. RESULTS: For the total score of the screening test, we calculated the 5th, 15th, 25th, and 50th percentiles for two education groups. The analyses allowed the identification of cutoff and alert scores based on education level. CONCLUSIONS: With the present study, solid normative data for the DTLA derived from the performance of 694 healthy, community-dwelling adults, and elderly people are now available to clinicians and researchers.

Lower Education and Reading and Writing Habits Are Associated With Poorer Oral Discourse Production in Typical Adults and Older Adults.

During normal aging there is a decline in cognitive functions that includes deficits in oral discourse production. A higher level of education and more frequent reading and writing habits (RWH) might delay the onset of the cognitive decline during aging. This study aimed at investigating the effect of education and RWH on oral discourse production in older adults. Picture-based narratives were collected from 117 healthy adults, aged between 51 and 82 years (68.6 ± 6.38) with 0-20 years of formal education (10.1 ± 5.69). Measures of macro, microlinguistic and modalizations were computed and entered as dependent variables in hierarchical regression analyses that included age, education and RWH as regressors. Results revealed that higher education explained a better performance at the macrostructure and microstructure dimensions. Higher frequency of RWH explained the production of fewer modalizations. These results demonstrate the positive effect of education and RWH in oral discourse production in older adults. Therefore, higher attention should be given to these social factors.

The Importance of Being Familiar: The Role of Semantic Knowledge in the Activation of Emotions and Factual Knowledge from Music in the Semantic Variant of Primary Progressive Aphasia.

BACKGROUND: The role of semantic knowledge in emotion recognition remains poorly understood. The semantic variant of primary progressive aphasia (svPPA) is a degenerative disorder characterized by progressive loss of semantic knowledge, while other cognitive abilities remain spared, at least in the early stages of the disease. The syndrome is therefore a reliable clinical model of semantic impairment allowing for testing the propositions made in theoretical models of emotion recognition. OBJECTIVE: The main goal of this study was to investigate the role of semantic memory in the recognition of basic emotions conveyed by music in individuals with svPPA. METHODS: The performance of 9 individuals with svPPA was compared to that of 32 control participants in tasks designed to investigate the ability: a) to differentiate between familiar and non-familiar musical excerpts, b) to associate semantic concepts to musical excerpts, and c) to recognize basic emotions conveyed by music. RESULTS: Results revealed that individuals with svPPA showed preserved abilities to recognize familiar musical excerpts but impaired performance on the two other tasks. Moreover, recognition of basic emotions and association of musical excerpts with semantic concepts was significantly better for familiar than non-familiar musical excerpts in participants with svPPA. CONCLUSION: Results of this study have important implications for theoretical models of emotion recognition and music processing. They suggest that impairment of semantic memory in svPPA affects both the activation of emotions and factual knowledge from music and that this impairment is modulated by familiarity with musical tunes.

Avaliação da produção discursiva oral no envelhecimento e sua relação com escolaridade e hábitos de leitura e escrita: uma revisão sistemática / Assessment of oral discourse production in aging and their relation with schooling and reading and writing habits: a systematic review

A presente revisão sistemática tem por objetivo verificar quais as tarefas comumente utilizadas para elucidação da produção discursiva oral do adulto idoso e sua relação com escolaridade e hábitos de leitura e escrita. Para tanto, buscaram-se artigos publicados nas bases de dados Scopus, Web of Science, PubMed, MEDLINE e LILACS. Os termos utilizados foram ("discourse production" OR "oral production" OR "narrative production") AND (aging OR elderly OR "older adults") AND (education OR schooling OR "reading habits" OR "writing habits"). Os critérios de seleção incluíram: (a) artigo original avaliado por pares; (b) com foco na produção discursiva oral no envelhecimento típico; (c) publicado entre 1990 e 2019. Foram encontrados, no total, 456 registros, dos quais 393 foram excluídos pelo título e 12 após leitura na íntegra, por não se relacionarem ao tema. De acordo com os critérios de seleção, 19 artigos foram selecionados. Verificou-se que grande parte das pesquisas utiliza tarefas baseadas em estímulos visuais, sobretudo em seu formato sequencial, enquanto uma pequena parte utiliza tarefas baseadas em eventos autobiográficos, conversações livres ou descrição de procedimentos. Algumas pesquisas compararam a produção discursiva oral da amostra em questão em diferentes tarefas. Poucos estudos incluíram a variável escolaridade em seus experimentos, enquanto nenhum estudo investigou o efeito dos hábitos de leitura e escrita. Devido à sua complexidade, estudos no nível do discurso precisam considerar a influência do tipo de tarefa para a elucidação do processamento, assim como fatores sociodemográficos e culturais dos seus participantes.(AU)

This systematic review aims at verifying which tasks have commonly been used to elucidate oral discourse produced by elderly adults and their relation with cultural aspects, such as schooling and reading and writing habits. Articles published on Scopus, Web of Science, PubMed, MEDLINE and LILACS data bases were searched. The descriptors used were ("discourse production" OR "oral production" OR "narrative production") AND (aging OR elderly OR "older adults") AND (education OR schooling OR "reading habits" OR "writing habits"). The selection criteria were: (a) original peer-reviewed articles; (b) with a focus on oral discourse production in typical aging; (c) published between 1990 and 2019. A total of 456 registers were found, from which 393 were excluded by reading their title and 12 after reading them entirely, for not having relation with the topic. According to the selection criteria, 19 articles were selected. The analyses showed that the great majority of the studies utilize tasks based on visual stimuli, mainly on their sequential form, while a reduced number uses tasks based on autobiographical events, free conversations or description of procedures. Some studies compared the oral discourse production of this population in several tasks. Few studies included the variable of schooling in their experi ments, while no study investigated the effect of reading and writing habits. Due to their complexity, studies on discourse level should take into consideration the influence of task typology to elucidate processing, together with socio-demographic and cultural aspects of their participants.(AU)

Age-preserved semantic memory and the CRUNCH effect manifested as differential semantic control networks: An fMRI study.

Semantic memory representations are overall well-maintained in aging whereas semantic control is thought to be more affected. To explain this phenomenon, this study aims to test the predictions of the Compensation Related Utilization of Neural Circuits Hypothesis (CRUNCH) focusing on task demands in aging as a possible framework. The CRUNCH effect would manifest itself in semantic tasks through a compensatory increase in neural activation in semantic control network regions but only up to a certain threshold of task demands. This study will compare 40 young (20-35 years old) with 40 older participants (60-75 years old) in a triad-based semantic judgment task performed in an fMRI scanner while manipulating levels of task demands (low vs. high) through semantic distance. In line with the CRUNCH predictions, differences in neurofunctional activation and behavioral performance (accuracy and response times) are expected in young vs. old participants in the low- vs. high-demand conditions manifested in semantic control Regions of Interest.

Low Speech Connectedness in Alzheimer's Disease is Associated with Poorer Semantic Memory Performance.

Connected speech is an everyday activity. We aimed to investigate whether connected speech can differentiate oral narrative production between adults with Alzheimer's disease (AD; n = 24) and cognitively healthy older adults (n = 48). We used graph attributes analysis to represent connected speech. Participants produced oral narratives and performed semantic, episodic, and working memory tasks. AD patients produced less connected narratives than cognitively healthy older adults. Connectedness was associated with semantic memory in AD and with episodic memory in controls. Word-graphs connectedness represents a practical tool to assess cognitive impairment in AD patients.

TDQ-30-A New Color Picture-Naming Test for the Diagnostic of Mild Anomia: Validation and Normative Data in Quebec French Adults and Elderly.

OBJECTIVE: A reduction in lexical access is observed in normal aging and a few studies also showed that this ability is affected in individuals with subjective cognitive decline. Lexical access is also affected very early in mild cognitive impairment as well as in major neurocognitive disorders. The detection of word-finding difficulties in the earliest stages of pathological aging is particularly difficult because symptoms are often subtle or mild. Therefore, mild anomia is underdiagnosed, mainly due to the lack of sensitivity of naming tests. In this article, we present the TDQ-30, a new picture-naming test designed to detect mild word-finding deficits in adults and elderly people. METHOD: The article comprises three studies aiming at the development of the test (Study 1), the establishment of its validity and reliability (Study 2), and finally, the production of normative data for French-speaking adults and elderly people from Quebec (Study 3). RESULTS: The results showed that the TDQ-30 has good convergent validity. Also, the TDQ-30 distinguished the performance of healthy controls from those of participants with mild cognitive impairment, Alzheimer's disease, and post-stroke aphasia. This suggests good discriminant validity. Finally, this study provides normative data computed from a study sample composed of 227 participants aged 50 years and over. CONCLUSIONS: The TDQ-30 has the potential to become a valuable picture-naming test for the diagnosis of mild anomia associated with pathological aging.

Semantic Processing in Healthy Aging and Alzheimer's Disease: A Systematic Review of the N400 Differences.

Semantic deficits are common in individuals with Alzheimer's disease (AD). These deficits notably impact the ability to understand words. In healthy aging, semantic knowledge increases but semantic processing (i.e., the ability to use this knowledge) may be impaired. This systematic review aimed to investigate semantic processing in healthy aging and AD through behavioral responses and the N400 brain event-related potential. The results of the quantitative and qualitative analyses suggested an overall decrease in accuracy and increase in response times in healthy elderly as compared to young adults, as well as in individuals with AD as compared to age-matched controls. The influence of semantic association, as measured by N400 effect amplitudes, appears smaller in healthy aging and even more so in AD patients. Thus, semantic processing differences may occur in both healthy and pathological aging. The establishment of norms of healthy aging for these outcomes that vary between normal and pathological aging could eventually help early detection of AD.

Questionnaire Sémantique de Québec (QueSQ). Développement, validation et normalisation.

The main objective of this study was to present the development, validation and normalization of the Quebec Semantic Questionnaire (QueSQ). The QueSQ is a 12-item questionnaire designed for the rapid screening of semantic disorders. Psycholinguistic parameters that can influence performance, such as the nature of semantic features and superordinate semantic categories, were taken into account during its development. Psychometric qualities of QueSQ were demonstrated during the validation process. QueSQ normative data were established on the basis of age and level of education, from a sample of 100 Franco-Quebecers aged 50 years and over.

L'objectif principal de cet article est de présenter le développement, la validation et la normalisation du Questionnaire Sémantique de Québec (QueSQ). Le QueSQ est un questionnaire comportant 12 items, permettant le dépistage rapide des troubles sémantiques. Il a été conçu en tenant compte des paramètres psycholinguistiques pouvant influencer la performance, soit la nature des traits sémantiques et la catégorie sémantique superordonnée. L'étude de validation a permis de mettre en évidence certaines des qualités psychométriques du QueSQ. Les données normatives du QueSQ, établies en fonction de l'âge et du niveau de scolarité, ont été obtenues auprès de 100 personnes franco-québécoises âgées de 50 ans et plus.

MorphoLex-FR: A derivational morphological database for 38,840 French words.

Studies on morphological processing in French, as in other languages, have shown disparate results. We argue that a critical and long-overlooked factor that could underlie these diverging results is the methodological differences in the calculation of morphological variables across studies. To address the need for a common morphological database, we present MorphoLex-FR, a sizeable and freely available database with 12 variables for prefixes, roots, and suffixes for the 38,840 words of the French Lexicon Project. MorphoLex-FR constitutes a first step to render future studies addressing morphological processing in French comparable. The procedure we used for morphological segmentation and variable computation is effectively the same as that in MorphoLex, an English morphological database. This will allow for cross-linguistic comparisons of future studies in French and English that will contribute to our understanding of how morphologically complex words are processed. To validate these variables, we explored their influence on lexical decision latencies for morphologically complex nouns in a series of hierarchical regression models. The results indicated that only morphological variables related to the suffix explained lexical decision latencies. The frequency and family size of the suffix exerted facilitatory effects, whereas the percentage of more frequent words in the morphological family of the suffix was inhibitory. Our results are in line with previous studies conducted in French and in English. In conclusion, this database represents a valuable resource for studies on the effect of morphology in visual word processing in French.

The relationship between morphological awareness and reading comprehension in Spanish-speaking children.

In the last decades, a series of studies has explored the role of morphological awareness on reading comprehension. Path analysis studies performed in English have shown that morphological awareness benefits reading comprehension both directly and indirectly, through word decoding. This issue has seldom been explored in Spanish. The aim of this study was to replicate in Spanish the results previously found in English. We used path analysis to assess three alternative models of the relationship between morphological awareness, word decoding and reading comprehension in 4th grade Spanish-speaking children. Contrary to English, we found that morphological awareness benefits reading comprehension only directly. We conclude that in Spanish, in which accurate and fluent pronunciation of written words can be achieved through grapheme-to-phoneme conversion rules, morphological awareness does not help the correct pronunciation of words. Thus, morphological awareness is not relevant for word decoding in Spanish but is related to reading comprehension since this type of morphological knowledge provides access to the semantic and syntactic information of new words.

The role of the hippocampus in the semantic variant of primary progressive aphasia: A resting-state fcMRI study.

The goal of the study was to determine whether the semantic variant of primary progressive aphasia (svPPA) affects the intrinsic connectivity network anchored to left and right anterior hippocampus, but spares the posterior hippocampus. A resting-state functional connectivity MRI (rs-fcMRI) study was conducted in a group of patients with svPPA and in controls, using a seed-to-voxel approach. In comparison to controls, massively reduced connectivity was found in the anterior hippocampus, mainly the left one, for svPPA patients but not in the left or right posterior hippocampus. In svPPA, the anterior hippocampus showed reduced functional connectivity with regions implicated in the semantic memory network. Significant correlation was also found between the functional connectivity strength of the left anterior hippocampus and the ventromedial cortex, and performance in semantic tasks. These findings indicate that the functional disconnection of the anterior hippocampus may be a promising in vivo biomarker of svPPA and illustrate the role of this hippocampal subregion in the semantic memory system.

Morphological De-com-pos-it-ion Helps Recognize Low-er Frequency Words in Typically Developing Spanish-Speaking Children.

Several studies in Spanish and other languages have shown that, in a lexical decision task, children are more likely to accept pseudowords with a known morphological structure as words as compared to non-morphological pseudowords. Morphology also facilitates visual word recognition of actual words in children with reading difficulties. In the present study, we explored the role of morphology, frequency and reading proficiency (measured by school grade) in visual word recognition. Typically developing readers of Spanish from 2nd, 4th and 6th grades performed a lexical decision task in which the morphological complexity and the frequency of the words were factorially manipulated. Our results showed that morphology benefited the accuracy of visual word recognition for low frequency words only. We conclude that decomposition in morphemes occurs in Spanish only for less frequent words. These results in Spanish support models that posit the decomposition of morphologically complex words in the orthographic lexicon.

White Matter Damage in the Semantic Variant of Primary Progressive Aphasia.

BACKGROUND: The semantic variant of primary progressive aphasia (svPPA) is a form of dementia, mainly featuring language impairment, for which the extent of white matter (WM) damage is less described than its associated grey matter (GM) atrophy. Our study aimed to characterise the extent of this damage using a sensitive and unbiased approach. METHODS: We conducted a between-group study comparing 10 patients with a clinical diagnosis of svPPA, recruited between 2011 and 2014 at a tertiary reference centre, with 9 cognitively healthy, age-matched controls. From diffusion tensor imaging (DTI) data, we extracted fractional anisotropy (FA) values using a tract-based spatial statistics approach. We further obtained GM volumetric data using the Freesurfer automated segmentation tool. We compared both groups using non-parametric Wilcoxon rank-sum tests, correcting for multiple comparisons. RESULTS: Demographic data showed that patients and controls were comparable. As expected, clinical data showed lower results in svPPA than controls on cognitive screening tests. Tractography showed impaired diffusion in svPPA patients, with FA mostly decreased in the longitudinal, uncinate, cingulum and external capsule fasciculi. Volumetric data show significant atrophy in svPPA patients, mostly in the left entorhinal, amygdala, inferior temporal, middle temporal, superior temporal and temporal pole cortices, and bilateral fusiform gyri. CONCLUSIONS: This syndrome appears to be associated not only with GM but also significant WM degeneration. Thus, DTI could play a role in the differential diagnosis of atypical dementia by specifying WM damage specific to svPPA.

Des atteintes à la substance blanche du cerveau dans le cas de la variante sémantique de l'aphasie primaire progressive. Contexte: La variante dite « sémantique ¼ de l'aphasie primaire progressive (vsAPP) constitue une forme de démence de laquelle découlent principalement des troubles du langage. À l'inverse de l'atrophie de la substance grise associée à cette démence, on a été moins portés à décrire les atteintes à la substance blanche. Notre étude entend donc cerner l'étendue de ces atteintes au moyen d'une approche à la fois sensible et neutre. Méthodes: Nous avons effectué une étude intergroupe en comparant 10 patients ayant reçu un diagnostic clinique de vsAPP à 9 témoins en santé sur le plan cognitif. À noter que ces 10 patients ont été recrutés entre 2011 et 2014 dans un centre de soins médicaux tertiaires. C'est à partir de données obtenues grâce à l'imagerie par tenseur de diffusion (diffusion tensor imaging) que nous avons extrait, au moyen d'une approche privilégiant les statistiques spatiales basées sur les voies neuronales, des valeurs d'anisotropie fractionnelle (FA). Nous avons en outre obtenu des données volumétriques concernant la substance grise en utilisant l'outil de segmentation automatisée Freesurfer. Nous avons ensuite comparé ces deux groupes à l'aide de tests des rangs signés de Wilcoxon non-paramétriques, et ce, en veillant à appliquer une correction en vue de nombreuses comparaisons. Résultats: D'entrée de jeu, précisons que nos données démographiques ont révélé que les patients et les témoins étaient comparables. Comme il fallait s'y attendre, nos données cliniques ont montré, dans le cadre de tests de dépistage cognitif, que les résultats des patients atteints de vsAPP se sont révélés inférieurs à ceux des témoins. Des examens de tractographie ont par ailleurs montré une diffusion déficiente chez ces 10 patients, les valeurs de FA ayant surtout diminué dans les faisceaux longitudinaux et uncinés, dans le cingulum et la capsule externe. Quant à nos données volumétriques, elles ont révélé une atrophie notable chez les patients atteints de vsAPP, surtout dans les régions suivantes : cortex entorhinal gauche, amygdale, temporale inférieure, mésiotemporale, temporale supérieure, cortex temporo-polaires et lobules fusiformes bilatéraux. Conclusions: Le syndrome évoqué ci-dessus semble être associé non seulement à une dégénérescence de la substance grise mais aussi à une dégénérescence importante de la substance blanche. En précisant de manière spécifique l'atteinte à la substance blanche que sous-tend la vsAPP, l'imagerie par tenseur de diffusion pourrait donc être appelée à jouer un rôle dans l'établissement de diagnostics différentiels pour des démences atypiques.

Differential language network functional connectivity alterations in Alzheimer's disease and the semantic variant of primary progressive aphasia.

Patients with Alzheimer's disease (AD) and semantic variant primary progressive aphasia (svPPA) can present with similar language impairments, mainly in naming. It has been hypothesized that these deficits are associated with different brain mechanisms in each disease, but no previous study has used a network approach to explore this hypothesis. The aim of this study was to compare resting-state functional magnetic resonance imaging (rs-fMRI) language network in AD, svPPA patients, and cognitively unimpaired elderly adults (CTRL). Therefore, 10 AD patients, 12 svPPA patients and 11 CTRL underwent rs-fMRI. Seed-based functional connectivity analyses were conducted using regions of interest in the left anterior temporal lobe (ATL), left posterior middle temporal gyrus (pMTG) and left inferior frontal gyrus (IFG), applying a voxelwise correction for gray matter volume. In AD patients, the left pMTG was the only key language region showing functional connectivity changes, mainly a reduced interhemispheric functional connectivity with its right-hemisphere counterpart, in comparison to CTRL. In svPPA patients, we observed a functional isolation of the left ATL, both decreases and increases in functional connectivity from the left pMTG and increased functional connectivity form the left IFG. Post-hoc analyses showed that naming impairments were overall associated with the functional disconnections observed across the language network. In conclusion, AD and svPPA patients present distinct language network functional connectivity profiles. In AD patients, functional connectivity changes were restricted to the left pMTG and were overall less severe in comparison to svPPA patients. Results in svPPA patients suggest decreased functional connectivity along the ventral language pathway and increased functional connectivity along the dorsal language pathway. Finally, the observed connectivity patterns are overall consistent with previously reported structural connectivity and language profiles in these patients.