Evaluation de la réorganisation cérébrale du langage chez les patients épileptiques. Apport de la psychologie cognitive

National audienceL'objectif de cet article est de rappeler les exigences spécifiques nécessaires à la mise en place d'un paradigme d'activation en IRMf dans le cadre de l'évaluation fonctionnelle du langage lors du bilan pré- et post-chirurgical de l'épilepsie

Preserved and impaired emotional memory in Alzheimer's disease.

International audiencePatients with early atrophy of both limbic structures involved in memory and emotion processing in Alzheimer's disease (AD) provide a unique clinical population for investigating how emotion is able to modulate retention processes. This review focuses on the emotional enhancement effect (EEE), defined as the improvement of memory for emotional events compared with neutral ones. The assessment of the EEE for different memory systems in AD suggests that the EEE could be preserved under specific retrieval instructions. The first part of this review examines these data in light of compelling evidence that the amygdala can modulate processes of hippocampus-dependent memory. We argue that the EEE could be a useful paradigm to reduce impairment in episodic memory tasks. In the second part, we discuss theoretical consequences of the findings in favor of an EEE, according to which a compensatory mechanism in patients with AD solicits greater amygdala functioning or additional networks, even when amygdala atrophy is present. These considerations emphasize the relevance of investigating patients with AD to understand the relationship between emotion and memory processes

The left inferior frontal gyrus under focus: an fMRI study of the production of deixis via syntactic extraction and prosodic focus: An fMRI study of the production of deixis

International audienceThe left inferior frontal gyrus (LIFG, BA 44, 45, 47) has been associated with linguistic processing (from sentence- to syllable- parsing) as well as action analysis. We hypothesize that the function of the LIFG may be the monitoring of action, a function well adapted to agent deixis (verbal pointing at the agent of an action). The aim of this fMRI study was therefore to test the hypothesis that the LIFG is involved during the production of agent deixis. We performed an experiment whereby three kinds of deictic sentences were pronounced, involving prosodic focus, syntactic extraction and prosodic focus with syntactic extraction. A common pattern of activation was found for the three deixis conditions in the LIFG (BA 45 and/or 47), the left insula and the bilateral premotor (BA 6) cortex. Prosodic deixis additionally activated the left anterior cingulate gyrus (BA 24, 32), the left supramarginal gyrus (LSMG, BA 40) and Wernicke's area (BA 22). Our results suggest that the LIFG is involved during agent deixis, through either prosody or syntax, and that the LSMG and Wernicke's area are additionally required in prosody-driven deixis. Once grammaticalized, deixis would be handled solely by the LIFG, without the LSMG and Wernicke's area

Dynamic causal modeling of spatiotemporal integration of phonological and semantic processes: an electroencephalographic study.: DCM of phonology and semantics

International audienceIntegration of phonological and lexicosemantic processes is essential for visual word recognition. Here we used dynamic causal modeling of event-related potentials, combined with group source reconstruction, to estimate how those processes translate into context-dependent modulation of effective connectivity within the temporal-frontal language network. Fifteen healthy human subjects performed a phoneme detection task in pseudo-words and a semantic categorization task in words. Cortical current densities revealed the sequential activation of temporal regions, from the occipital-temporal junction toward the anterior temporal lobe, before reaching the inferior frontal gyrus. A difference of activation between phonology and semantics was identified in the anterior temporal lobe within the 240-300 ms peristimulus time window. Dynamic causal modeling indicated this increase of activation of the anterior temporal lobe in the semantic condition as a consequence of an increase of forward connectivity from the posterior inferior temporal lobe to the anterior temporal lobe. In addition, fast activation of the inferior frontal region, which allowed a feedback control of frontal regions on the superior temporal and posterior inferior temporal cortices, was found to be likely. Our results precisely describe spatiotemporal network mechanisms occurring during integration of phonological and semantic processes. In particular, they support the hypothesis of multiple pathways within the temporal lobe for language processing, where frontal regions would exert a top-down control on temporal regions in the recruitment of the anterior temporal lobe for semantic processing

Cerebral Correlates of Emotional and Action Appraisals During Visual Processing of Emotional Scenes Depending on Spatial Frequency: A Pilot Study.

International audienceVisual processing of emotional stimuli critically depends on the type of cognitive appraisal involved. The present fMRI pilot study aimed to investigate the cerebral correlates involved in the visual processing of emotional scenes in two tasks, one emotional, based on the appraisal of personal emotional experience, and the other motivational, based on the appraisal of the tendency to action. Given that the use of spatial frequency information is relatively flexible during the visual processing of emotional stimuli depending on the task's demands, we also explored the effect of the type of spatial frequency in visual stimuli in each task by using emotional scenes filtered in low spatial frequency (LSF) and high spatial frequencies (HSF). Activation was observed in the visual areas of the fusiform gyrus for all emotional scenes in both tasks, and in the amygdala for unpleasant scenes only. The motivational task induced additional activation in frontal motor-related areas (e.g. premotor cortex, SMA) and parietal regions (e.g. superior and inferior parietal lobules). Parietal regions were recruited particularly during the motivational appraisal of approach in response to pleasant scenes. These frontal and parietal activations, respectively, suggest that motor and navigation processes play a specific role in the identification of the tendency to action in the motivational task. Furthermore, activity observed in the motivational task, in response to both pleasant and unpleasant scenes, was significantly greater for HSF than for LSF scenes, suggesting that the tendency to action is driven mainly by the detailed information contained in scenes. Results for the emotional task suggest that spatial frequencies play only a small role in the evaluation of unpleasant and pleasant emotions. Our preliminary study revealed a partial distinction between visual processing of emotional scenes during identification of the tendency to action, and during identification of personal emotional experiences. It also illustrates flexible use of the spatial frequencies contained in scenes depending on their emotional valence and on task demands

Multimodal Perception of Prosodic Contrastive Focus in French: A Preliminary fMRI Study

http://www.zas.gwz-berlin.de/events/summerschool_2007/index.htmInternational audienceContrastive focus is used to emphasize a word or group of words in an utterance as opposed to another. In French, it can be conveyed by prosody using a specific intonational contour on the constituent pointed at (XXXf a mangé la pomme. 'XXXf ate the apple.'). It remains unclear what neural processes underlie the perception of prosodic focus. Meanwhile studies have shown that prosodic processing in general cannot be restricted to the right hemisphere (see [1] for review). Moreover it appears ([2]) that even though the perception of prosodic focus was often considered as uniquely auditory, it is possible to perceive prosodic focus visually and the visual modality can enhance perception when prosodic auditory cues are degraded (whispered speech). This finding emphasizes the necessity to consider the perception of prosodic contrastive focus and speech prosody in general as multimodal. The aim of this study is to analyze the neural processing of prosodic focus from a multimodal point of view

Réorganisation du conduit vocal et réorganisation corticale de la parole : de la perturbation aux lèvres à la glossectomie. Études acoustiques et IRMf

21 pagesRetrouver l'usage de la langue - articulateur central de la parole - pour produire les dix voyelles du français, et ce après une opération de glossectomie suivie d'une reconstruction linguale à base d'un muscle de la cuisse (le gracilis), tel était le difficile problème que le patient K.H. (53 ans) a su résoudre au bout de neuf mois. Comment a-t-il pu apprendre à contrôler sa nouvelle " langue" pour produire les différentes voyelles de façon distincte ? C'est ce que nous avons cherché à comprendre dans cette étude. Nous avons mis en place un suivi expérimental longitudinal du patient en enregistrant ses productions acoustiques et son activité cérébrale juste avant l'opération, un mois après l'opération et neuf mois après l'opération. Nous avons ainsi pu suivre la récupération corticale du sujet, en l'occurrence la re-latéralisation dans l'hémisphère gauche pour l'articulation des catégories vocaliques de sa langue, en relation avec l'amélioration de ses performances articulatoires et acoustiques. Plus fondamentalement, cette prouesse atteste de la plasticité corticale phonologique via l'équifinalité compensatoire du système de la langue, en l'occurrence par le jeu des équivalence motrices et acoustiques

Cerebral correlates of multimodal pointing: An fmri study of prosodic focus, syntactic extraction, digital- and ocular- pointing

International audienceDeixis or pointing plays a crucial role in language acquisition and speech communication and can be conveyed in several modalities. The aim of this paper is to explore the cerebral substrate of multimodal pointing actions. We present an fMRI study of pointing including: 1) index finger pointing, 2) eye pointing, 3) prosodic focus production, 4) syntactic extraction (during speech production). Fifteen subjects were examined while they gave digital, ocular and oral responses inside the 3T imager. Results of a random effect group analysis show that digital and prosodic pointings recruit the parietal lobe bilaterally, while ocular and syntactic pointings do not. A grammaticalization process is suggested to explain the lack of parietal activation in the syntactic condition. Further analyses are carried out on the link between digital and prosodic parietal activations

Représentations cérébrales des articulateurs de la parole

National audienceIn order to localize cerebral regions involved in articulatory control processes, ten subjects were examined using functional magnetic resonance imaging while executing lip, tongue and jaw movements. Although the three motor tasks activated a set of common brain areas classically involved in motor control, distinct movement representation sites were found in the motor cortex. These results support and extend previous brain imaging studies by demonstrating a sequential dorsoventral somatotopic organization of lips, jaw and tongue in the motor cortex