Showing papers by "Francis Eustache published in 2014"

Relationship between brain volumetric changes and interim drinking at six months in alcohol-dependent patients.

Abstract: Background Chronic alcohol consumption results in brain damage potentially reversible with abstinence. It is however difficult to gauge the degree of recovery of brain tissues with abstinence since changes are subtle and a significant portion of patients relapse. State-of-the-art morphometric methods are increasingly used in neuroimaging studies to detect subtle brain changes at a voxel level. Our aim was to use the most refined morphometric methods to observe in alcohol dependence the relationship between volumetric changes and interim drinking over a 6-month follow-up. Methods Overall, 19 patients with alcohol dependence received volumetric T1-weighted magnetic resonance imaging (MRI) after detoxification. A 6-month follow-up study was then conducted, during which 11 of them received a second MRI scan. First, correlations were conducted between gray matter (GM) and white matter (WM) volumes of patients at alcohol treatment entry and the amount of alcohol consumed between treatment entry and follow-up. Second, longitudinal analyses were performed from pairs of MRI scans using tensor-based morphometry in the 11 patients, and correlations were computed between the resultant Jacobian maps of GM and WM and interim drinking. Results Our preliminary results showed that, among others, alcoholics with smaller thalamus at alcohol treatment entry tended to resume with heavy alcohol consumption (p < 0.005 uncorrected [unc.]). Our longitudinal study revealed an overall inverse relationship between recovery of brain structures like the cerebellum, striatum, and cingulate gyrus, and the amount of alcohol consumed over the 6-month follow-up (p < 0.005 unc.). The recovery could be observed not only with strict abstinence but also in cases of moderate resumption of alcohol consumption, when there had been no drastic relapse into alcohol dependence. Conclusions Those preliminary findings indicate that the volume of the thalamus at treatment entry may have an influence on subsequent interim drinking. There is recovery of certain brain regions even when patients resume with moderate, but not drastic, alcohol consumption.

How do we process event-based and time-based intentions in the brain? an fMRI study of prospective memory in healthy individuals.

Abstract: Prospective memory (PM) refers to the ability to remember to do something in the future, either in response to an event (event-based) or after a certain amount of time has elapsed (time-based). While the distinction between event- and time-based PM is widely acknowledged in the literature, little is known about the processes they share and those they do not. This is particularly true concerning their brain substrates, as almost all neuroimaging studies so far have focused on event-based PM. We proposed a functional magnetic resonance imaging paradigm assessing both event-based and time-based PM to 20 healthy young individuals. Analyses revealed that event- and time-based PM both induced activation in the posterior frontal and parietal cortices, and deactivation in the medial rostral prefrontal cortex. In addition, activation more specific to each condition, which may underlie differences in strategic monitoring, was highlighted. Thus, occipital areas were more activated during event-based PM, probably reflecting target-checking, while a network comprising the dorsolateral prefrontal cortex, the cuneus/precuneus and, to a lesser extent, the inferior parietal lobule, superior temporal gyrus, and the cerebellum, was more activated in time-based PM, which may reflect the involvement of time-estimation processes. These results confirm the allocation of attentional resources to the maintenance of intention for event-based and time-based PM, as well as the engagement of distinct mechanisms reflecting the monitoring strategies specific to each condition.

Effects of age and alzheimer's disease on hippocampal subfields: comparison between manual and freesurfer volumetry

Abstract: Growing interest has developed in hippocampal subfield volumetry over the past few years and an increasing number of studies use the automatic segmentation algorithm implemented in FreeSur- fer. However, this approach has not been validated on standard resolution T1-weighted magnetic reso- nance (MR) as used in most studies. We aimed at comparing hippocampal subfield segmentation using FreeSurfer on standard T1-weighted images versus manual delineation on dedicated high-resolution hip- pocampal scans. Hippocampal subfields were segmented in 133 individuals including 98 cognitively normal controls aged 19-84 years, 17 mild cognitive impairment and 18 Alzheimer's disease (AD) patients using both methods. Intraclass correlation coefficients (ICC) and Bland-Altman plots were com- puted to assess the consistency between both methods, and the effects of age and diagnosis were assessed from both measures. Low to moderate ICC (0.31-0.74) were found for the subiculum and other subfields as well as for the whole hippocampus, and the correlations were very low for cornu ammonis (CA)1 (<0.1). FreeSurfer CA1 volume estimates were found to be much lower than those obtained from manual segmentation, and this bias was proportional to the volume of this structure so that no effect of age or AD could be detected on FreeSurfer CA1 volumes. This study points to the differences in the ana- tomic definition of the subfields between FreeSurfer and manual delineation, especially for CA1, and provides clue for improvement of this automatic technique for potential clinical application on standard T1-weighted MR. Hum Brain Mapp 00:000-000, 2014. V C 2014 Wiley Periodicals, Inc.

Chronic alcohol consumption and its effect on nodes of frontocerebellar and limbic circuitry: Comparison of effects in France and the United States

Abstract: Alcohol use disorders present a significant public health problem in France and the United States (U.S.), but whether the untoward effect of alcohol on the brain results in similar damage in both countries remains unknown. Accordingly, we conducted a retrospective collaborative investigation between two French sites (Caen and Orsay) and a U.S. laboratory (SRI/Stanford University) with T1-weighted, structural MRI data collected on a common imaging platform (1.5T, General Electric) on 288 normal controls (NC), 165 uncomplicated alcoholics (ALC), and 26 patients with alcoholic Korsakoff's syndrome (KS) diagnosed at all sites with a common interview instrument. Data from the two countries were pooled, then preprocessed and analyzed together at the U.S. site using atlas-based parcellation. National differences indicated that thalamic volumes were smaller in ALC in France than the U.S. despite similar alcohol consumption levels in both countries. By contrast, volumes of the hippocampus, amygdala, and cerebellar vermis were smaller in KS in the U.S. than France. Estimated amount of alcohol consumed over a lifetime, duration of alcoholism, and length of sobriety were significant predictors of selective regional brain volumes in France and in the U.S. The common analysis of MRI data enabled identification of discrepancies in brain volume deficits in France and the U.S. that may reflect fundamental differences in the consequences of alcoholism on brain structure between the two countries, possibly related to genetic or environmental differences. Hum Brain Mapp, 2014. © 2014 Wiley Periodicals, Inc.

Brain Activity and Functional Coupling Changes Associated with Self-Reference Effect during Both Encoding and Retrieval

Abstract: Information that is processed with reference to oneself, i.e. Self-Referential Processing (SRP), is generally associated with better remembering compared to information processed in a condition not related to oneself. This positive effect of the self on subsequent memory performance is called as Self-Reference Effect (SRE). The neural basis of SRE is still poorly understood. The main goal of the present work was thus to highlight brain changes associated with SRE in terms of activity and functional coupling and during both encoding and retrieval so as to assess the relative contribution of both processes to SRE. For this purpose, we used an fMRI event-related self-referential paradigm in 30 healthy young subjects and measured brain activity during both encoding and retrieval of self-relevant information compared to a semantic control condition. We found that SRE was associated with brain changes during the encoding phase only, including both greater activity in the medial prefrontal cortex and hippocampus, and greater functional coupling between these brain regions and the posterior cingulate cortex. These findings highlight the contribution of brain regions involved in both SRP and episodic memory and the relevance of the communication between these regions during the encoding process as the neural substrates of SRE. This is consistent with the idea that SRE reflects a positive effect of the reactivation of self-related memories on the encoding of new information in episodic memory.

Episodic future thinking in semantic dementia : a cognitive and fMRI study

Abstract: Semantic dementia (SD) is characterized by gradual loss of semantic memory. While episodic autobiographical memory seems relatively preserved, behavioral studies suggest that episodic future thinking is impaired. We used fMRI to measure brain activity in four SD patients (JPL, EP, LL, EG) while they envisioned future events and remembered personal past events. Twelve healthy elders served as controls. Episodic quality, emotion, mental imagery and level of consciousness (via remember/know judgements) were checked at debriefing. We analyzed the future compared to the past for each patient. All patients presented lateral temporal atrophy, but varied in terms of frontal and anterior hippocampal atrophy. Patient JPL presented atrophy in bilateral superior medial frontal gyri and left anterior hippocampus and was unable to engage in episodic future thinking, despite hyperactivations in frontal and occipital regions. Patient EP presented no atrophy in the anterior hippocampus, but atrophy in bilateral superior medial frontal gyrus and had difficulties to engage in episodic future thinking. Patient LL presented atrophy in left anterior hippocampus, but hyperactivated its right counterpart for future compared to past thinking, permitting her to project efficiently in the future in an episodic way. Patient EG presented no atrophy in the superior medial frontal gyri or anterior hippocampi and was able to engage in episodic future thinking. Altogether, patients' future projections differed depending on the severity and localization of their atrophy. The functional integrity of bilateral superior medial frontal gyri and anterior hippocampus appear crucial for episodic future thinking: atrophy of both structures strongly impairs future projection, while integrity of these structures or hyperactivation of residual tissue normalizes episodic future projection.

Component processes of memory in alcoholism: pattern of compromise and neural substrates.

Abstract: Initially, alcohol-related memory deficits were considered only through the prism of Korsakoff's syndrome (KS). It is now clear, however, that chronic alcohol consumption results in memory disorders in alcoholics without ostensible neurologic complications, such as Wernicke's encephalopathy and KS. Most of the principal memory components are affected, including working memory, episodic memory, semantic memory, perceptual memory, and procedural memory. The extent of those cognitive impairments depends on several factors, such as age, gender, nutritional status, and psychiatric comorbidity. While memory disorders, especially episodic memory deficits, are largely definitive in patients with KS, recovery of memory abilities has been described with abstinence in uncomplicated alcoholics. Neuropsychologic impairments, and especially memory disorders, must be evaluated at alcohol treatment entry because they could impede patients from benefiting fully from cognitive and behavioral treatment approaches for alcohol dependence. Screening of memory deficits could also enable clinicians to detect, among alcoholics without ostensible neurologic complications, those at risk of developing permanent and debilitating amnesia that features KS.

Musical practice and cognitive aging: two cross-sectional studies point to phonemic fluency as a potential candidate for a use-dependent adaptation

Abstract: Because of permanent use-dependent cerebral plasticity, all lifelong individuals’ experiences are believed to influence the cognitive aging quality. In old individuals, both former and current musical practices have been associated with better verbal skills, visual memory, processing speed, and planning function. This work sought for an interaction between musical practice and cognitive aging by comparing musician and nonmusician individuals for two periods of life (late adulthood and old age). Long-term memory, auditory verbal short-term memory, processing speed, nonverbal reasoning, and verbal fluencies were assessed. In study 1, measures of processing speed and auditory verbal short-term memory showed significant better performances for musicians compared with controls, but both groups displayed the same age-related difference. For verbal fluencies, musician individuals scored higher and displayed different age effects compared with controls. In study 2, we revealed that the life period at training onset (childhood versus adulthood) was associated with phonemic, but not semantic fluency performances (musicians who had started practice in adulthood did not perform better on phonemic fluency compared with nonmusicians). For these two measures, current frequency of training did not account for musicians’ scores. These patterns of results are discussed by confronting the hypothesis of a transformative effect of musical practice with non-causal explanation.

Brain Structural Substrates of Cognitive Procedural Learning in Alcoholic Patients Early in Abstinence

Abstract: Background: Procedural learning allows for the acquisition of new behavioral skills. Previous studies have shown that chronic alcoholism is characterized by impaired cognitive procedural learning and brain abnormalities a!ecting regions that are involved in the automation of new cognitive procedures in healthy individuals. The goal of the present study was to investigate the brain structural substrates of cognitive procedural learning in alcoholic patients (ALs) early in abstinence. Methods: Thirty-one ALs and 31 control participants (NCs) performed the Tower of Toronto task (4 daily learning sessions, each comprising 10 trials) to assess cognitive procedural learning. We also assessed episodic and working memory, executive functions, and visuospatial abilities. ALs underwent 1.5T structural magnetic resonance imaging. Results: The initial cognitive phase was longer in the AL group than in the NC group, whereas the autonomous phase was shorter. In ALs, the longer cognitive phase was predicted by poorer planning and visuospatial working memory abilities, and by smaller gray matter (GM) volumes in the angular gyrus and caudate nucleus. ALs’ planning abilities correlated with smaller GM volume in the angular gyrus. Conclusions: Cognitive procedural learning was impaired in ALs, with a delayed transition from the cognitive to the autonomous phase. This slowdown in the automation of the cognitive procedure was related to lower planning abilities, which may have hampered the initial generation of the procedure to be learned. In agreement with this neuropsychological finding, a persistent relationship was found between learning performance and the GM volumes of the angular gyrus and caudate nucleus, which are usually regarded as markers of planning and initial learning of the cognitive procedure.

Iconography : Impaired decision-making and brain shrinkage in alcoholism

Abstract: Abstract Alcohol-dependent individuals usually favor instant gratification of alcohol use and ignore its long-term negative consequences, reflecting impaired decision-making. According to the somatic marker hypothesis, decision-making abilities are subtended by an extended brain network. As chronic alcohol consumption is known to be associated with brain shrinkage in this network, the present study investigated relationships between brain shrinkage and decision-making impairments in alcohol-dependent individuals early in abstinence using voxel-based morphometry. Thirty patients performed the Iowa Gambling Task and underwent a magnetic resonance imaging investigation (1.5T). Decision-making performances and brain data were compared with those of age-matched healthy controls. In the alcoholic group, a multiple regression analysis was conducted with two predictors (gray matter [GM] volume and decision-making measure) and two covariates (number of withdrawals and duration of alcoholism). Compared with controls, alcoholics had impaired decision-making and widespread reduced gray matter volume, especially in regions involved in decision-making. The regression analysis revealed links between high GM volume in the ventromedial prefrontal cortex, dorsal anterior cingulate cortex and right hippocampal formation, and high decision-making scores (P < 0.001, uncorrected). Decision-making deficits in alcoholism may result from impairment of both emotional and cognitive networks.

Brain structural, functional, and cognitive correlates of recent versus remote autobiographical memories in mild cognitive impairment

Abstract: article i nfo Deficits in autobiographical memory appear earlier for recent than for remote life periods over the course of Alzheimer3sdisease(AD).Thepresentstudyaimstofurtherourunderstandingof thisgradedeffectbyinvestigat- ing the cognitive and neural substrates of recent versus remote autobiographical memories in patients with amnestic Mild Cognitive Impairment (aMCI) thanks to an autobiographical fluency task. 20 aMCI patients and 25 Healthy elderly Controls (HC) underwent neuropsychological tests assessing remote (20-to-30 years old) and recent (the ten last years) autobiographical memory as well as episodic and semantic memory, executive function and global cognition. All patients also had a structural MRI and an FDG-PET scan. Correlations were assessed between each autobiographical memory score and the other tests as well as grey matter volume and metabolism. Within the aMCI, performances for the remote period correlated with personal semantic memory and episodic memory retrieval whereas performances for the recent period only correlated with episodic mem- ory retrieval. Neuroimaging analyses revealed significant correlations between performances for the remote pe- riod and temporal pole and temporo-parietal cortex volumes and anterior cingulate gyrus metabolism, while performancesfortherecentperiodcorrelatedwithhippocampalvolumeandposteriorcingulate,medialprefron- tal and hippocampus metabolism. The brain regions related with the retrieval of events from the recent period showed greater atrophy/hypometabolisminaMCIpatients comparedtoHCthan those involvedinremote mem- ories.Recallofrecentmemoriesessentiallyreliesonepisodicmemory processesandbrainnetworkwhileremote memories also involve other processes such as semantic memory. This is consistent with the semanticization of

Autisme et connectivité cérébrale : contribution des études de neuroimagerie à la compréhension des signes cliniques

Abstract: Les donnees neuropsychologiques recueillies dans les troubles du spectre de l’autisme (TSA) mettent en evidence, de facon generale, une dissociation entre des competences dites de bas niveau preservees, et des deficits de traitement de haut niveau dans des domaines cognitifs varies. Ce pattern suggere l’existence d’un defaut d’integration de l’information entre les aires cerebrales posterieures, qui permettent un traitement sensoriel elementaire, et les aires cerebrales anterieures et notamment frontales, qui permettent un traitement complexe. L’integration de l’information entre les differentes aires cerebrales renvoie a la notion de connectivite anatomique mais aussi fonctionnelle et effective observee lors d’une tâche donnee. Le modele de la dysconnectivite dans l’autisme propose une explication de ces deficits par une sousconnectivite antero-posterieure et inter-hemispherique, generant un defaut d’integration de l’information par les aires cerebrales anterieures, tandis que les capacites preservees reposeraient sur une sur-connectivite au sein des aires cerebrales posterieures. Dans cette revue de la litterature, nous presentons des donnees recentes en imagerie cerebrale permettant une comprehension des principaux signes cliniques de l’autisme. Les etudes en IRM anatomique et fonctionnelle suggerent que les troubles du langage et de la communication reposent sur une sous-connectivite antero-posterieure, et les troubles comportementaux sur une surconnectivite sous-corticale. Nous confrontons ces resultats avec ceux obtenus avec d’autres techniques comme l’electroencephalographie (EEG) et aux etudes anatomo-pathologiques pour discuter des limites du modele de la dysconnectivite.

La mémoire, les amnésies et les lobes frontaux

Abstract: Classiquement, les processus de memoire, et notamment de memoire episodique, ont ete rattaches au fonctionnement du lobe temporal interne ou l’hippocampe joue un role cardinal. Le fonctionnement hippocampique s’inscrit dans un reseau plus vaste ou l’implication des lobes frontaux a ete soulignee. Leur role a ete progressivement precise grâce aux etudes menees en imagerie fonctionnelle cerebrale, tant chez le sujet sain, jeune et âge, que dans diverses pathologies mnesiques. Cette revue expose les principales conclusions de ces travaux.