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

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

Functional MRI and neuropsychological evidence for language plasticity before and after surgery in one patient with left temporal lobe epilepsy.

International audienceThis study explores the language reorganization before and after surgery in a 55-year-old right-handed female patient presenting with left temporal refractory epilepsy. Two aspects of language were explored, phonological and semantic, by using neuropsychological assessments and fMRI protocols. To assess the possible reorganization of language, fMRI results for B.L. were compared with results obtained in a group of healthy control subjects (results not presented in detail). According to our results and compared with healthy subjects, B.L. shows reorganization of temporal regions only. The reorganization had various patterns according to the task. Before surgery, neuropsychological testing in B.L. revealed impairment in phonological abilities and fMRI suggested right temporal involvement (interhemisphere reorganization) during the phonological task; semantic abilities were unaltered and fMRI showed bilateral activation of temporal regions during the semantic task. After surgery, the phonological deficit disappeared and fMRI showed left perilesional location of temporal activation (intrahemispheric reorganization); semantic abilities remain preserved and temporal activation remained located bilaterally but predominantly to the right during the semantic task. Our results suggest that cerebral reorganization of language depends on the language operation tested. Moreover, the results underline the importance of differential assessment of language operations and show functional reorganization after beneficial surgery in an older patient

An fMRI study of the perception of contrastive prosodic focus in French

International audienceThis fMRI study deals with the perception of prosodic contrastive focus in French. Twenty-two right-handed French participants listened to two kinds of utterances: with contrastive prosodic focus (Focus) and without (Neutral). The task was to judge whether the utterances contained focus. The Focus vs. Neutral contrast revealed bilateral activation of the inferior frontal, superior and middle temporal, premotor cortex and supramarginal gyri, as well as of the superior parietal lobule and anterior insula. Among these regions, the inferior frontal and supramarginal gyri, as well as the anterior insula, were significantly more activated to the left. These results suggest that the auditory perception of contrastive prosodic focus involves a large cerebral network which is partially predominant to the left

Who ate the candy? Neural processing of prosodic contrastive focus.

International audienceIntroduction. Considered as the melody of speech, the neural processing of prosody has long been assumed to be right-lateralized (Ross, 1981; Zatorre et al., 1992; Mayer et al., 2002). However, prosody often brings linguistic information and likely involves left-sided language areas (Baum & Pell, 1999; Astésano et al., 2004). One fine example is prosodic contrastive focus which is used to emphasize a constituent in an utterance as opposed to another using a specific intonational contour ('THOMASF mangeait le bonbon' / 'THOMASF ate the candy'). Previous studies have analyzed the processing of prosodic focus but either in an interlinguistic perspective (Tong et al., 2005) or in a framework of affective vs. linguistic comparison (Wildgruber et al., 2004). The aim of the present fMRI study is to clarify the neural network involved in the processing of prosodic contrastive focus in French and to examine potential hemispheric specialization. Methods. 22 French adults participated in the experiment. Two conditions were compared: Focus (F; utterances with narrow contrastive focus on the subject or the object) and Neutral (N; neutral broad focused utterances). The auditory sentences all had the same syntactic and syllabic structure (e.g., 'Thomas mangeait le bonbon' / 'Thomas ate the candy'). The task consisted in determining whether each auditory sentence contained contrastive focus or not. Responses were recorded and performance of task execution was evaluated. A random-effect group analysis was performed on the F vs. N contrast images (p < 0.001, uncorrected). In order to test possible hemispheric lateralization, Regions of Interest (ROI) analyses were carried-out. To this aim, ROIs were based on the whole-brain activation obtained by contrasting F vs. N in all subjects and delineated in the left and right hemispheres symmetrically. For each ROI, a repeated ANOVA was performed on the parameter estimates with the hemisphere as a within-subject factor. Results. Analysis of the correct responses confirmed that the tasks was perfectly performed (Focus: M = 92.99%, SD = 6.73%; Neutral: N = 97.72 %, SD = 3.85%). Compared to the neutral sentences, the processing of prosodic focus involved activations in the left premotor cortex, the inferior frontal gyrus bilaterally, the left superior and right middle temporal gyri, the supramarginal gyrus bilaterally, and the left superior parietal lobule (Group analysis; Figure 1-Panel A). In addition, left dominant activations were observed in the inferior frontal gyrus, the supramarginal gyrus and the anterior insula (ROi analyses; Figure1-Panel B). Conclusion. Altogether, these results demonstrate that the perception of prosodic focus is not strictly right-lateralized but rather involves bilateral processes in order to detect focus cues. The strong right middle temporal activation likely suggest that the melodic processing of the intonational contour rather takes place in the right hemisphere whereas the associative processes towards a linguistic decision would rather be left-lateralized (left dominance of superior temporal, parietal and frontal regions). This study provides evidence that that both hemispheres participate in the auditory perception of prosodic contrastive focus, with a left-dominant contribution for morpho-syntactic processes and thematic role monitoring

Neural correlates of the perception of prosodic focus in French: An fMRI study

International audienceThe studies of the neural correlates of the perception of prosody have led to different conclusions (for a review: Baum & Pell, 1999). The present functional magnetic brain imaging (fMRI) study deals with the perception of prosodic contrastive focus in French (example: Mary ate the apple? No, JOHN ate the apple; see Wildgruber et al., 2004; Tong et al., 2005 for related studies). Twenty-two right-handed French speakers participated in the experiment. The two conditions consisted in the auditory judgement of two kinds of utterances: with contrastive prosodic focus (Focus condition, Task) and without (Neutral condition, Control). The stimuli were delivered via headphones. The task was to judge whether the utterances contained focus or not. The subjects answered using two response keys. An event-related paradigm was designed (48 events per condition; 30 null-events). The behavioural responses were correct in more than 90% of the trials. The Focus vs. Neutral contrast revealed bilateral frontal activation (left BA 6 and BA 47 and right BA 44 and BA47), temporal activation (left BA 22 and right BA 21) and parietal activation (bilateral BA 40 and left BA 7). The Neutral vs. Focus contrast showed activation in the post-central gyrus (BA 1, 43) and left insula. A ROI analysis showed significant left hemisphere predominance for left inferior frontal (BA 47) and supramarginal (BA 40) gyri, as well as for left anterior insula (BA 13) during the Focus condition. Overall, these results suggest that the auditory perception of contrastive prosodic focus involves a left-dominant temporo-parieto-frontal network

Bilateral auditory and left-dominant premotor activity in prosodic focus processing

International audienceIntroduction: Contrastive focus is used to emphasize a constituent 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 (THOMASF a mangé la pomme. 'THOMASF ate the apple.'). The studies of the neural correlates of the perception of prosody have led to different conclusions (see Baum et al., 1199 for a review). Early works claimed that prosody is processed in the right hemisphere (e.g. Brådvik et al., 1991). Other studies have shown that prosodic processing cannot be restricted to the right hemisphere, however (e.g. Astésano et al.,2004). In this framework, this fMRI study deals with the perception of prosodic contrastive focus in French, according to the hemispheric specialization. Methods: An fMRI experiment was performed on 22 French adults (all were right-handed according to Oldfield, 1971). Two conditions were compared: 'sentences with narrow contrastive focus' (Focus condition, F) and 'sentences with broad focus' (Neutral condition, N). All sentences had the same syntactic and syllabic structure (e.g., 'Thomas cassait le vélo'. 'Thomas broke the bike'). The subjects were asked to judge whether the audio stimuli contained contrastive focus. The responses were recorded and the performance of task execution was evaluated. Functional MR imaging was performed on a Bruker 3T MR imager. Data analyses were performed by using SPM5 (www.fil.ion.ucl.ac.uk/spm). A random-effect group analysis on the F vs. N contrast images from individual analyses by using a one-sample t-test has been subsequently performed. We identified clusters of activated voxels (p 15). In addition, we defined seven Regions of Interest based on the whole-brain activation obtained by contrasting F vs. N in all subjects. ROIs were delineated in the left and right hemispheres symmetrically. For each ROI, the parameter estimates values were analyzed by means of a repeated ANOVA with hemisphere as a within-subject factor. Results: Behavioral responses obtained during the fMRI experiment were correct on most trials: Focus (M = 92.99%, SD = 6.73%) and Neutral (N = 97.72 %, SD = 3.85%). Our fMRI results showed significant left hemisphere predominance of the inferior frontal (BA 47) and supramarginal (BA 40) gyri, as well as for left anterior insula (BA 13) in the F vs. N contrast (c.f. Figure 1). Conclusions: Contrary to many brain imaging studies, these results suggest that both hemispheres participate in the auditory perception of prosody, but with a left-dominant contribution for morpho-syntactic processes and thematic role monitoring

Corrélats neurocognitifs de la perception de la focalisation prosodique contrastive en français

International audienceThe present event-related functional magnetic brain imaging (fMRI) study deals with the perception of prosodic contrastive focus in French. Twenty-two right-handed French speakers participated in the experiment. The two conditions consisted in the auditory judgement of two kinds of utterances: with contrastive prosodic focus (Focus condition, Task) and without (Neutral condition, Control). The participants had to judge whether the utterances contained focus or not. Our results suggest that both hemispheres participate in the auditory perception of contrastive prosodic focus, but with a left-dominant contribution for morpho-syntactic processes and thematic role monitoring