| Publications of year 2018 |
| Books |
| Theses |
| Articles in journals |
| Abstract: | The left hemisphere specialization for language is a well-established asymmetry in the human brain. Structural and functional asymmetries are observed as early as the prenatal period suggesting genetically determined differences between both hemispheres. The corpus callosum is a large tract connecting mostly homologous areas; some have proposed that it might participate in an enhancement of the left-hemispheric advantage to process speech. To investigate its role in early development, we compared 13 3-4-month-old infants with an agenesis of the corpus callosum ("AgCC") with 18 typical infants using high-density electroencephalography in an auditory task. We recorded event-related potentials for speech stimuli (syllables and babbling noise), presented binaurally (same syllable in both ears), monaurally (babbling noise in one ear) and dichotically (syllable in one ear and babbling noise in the other ear). In response to these stimuli, both groups developed an anterior positivity synchronous with a posterior negativity, yet the topography significantly differed between groups likely due to the atypical gyration of the medial surface in AgCC. In particular, the anterior positivity was lateral in AgCC infants while it covered the midline in typical infants. We then measured the latencies of the main auditory response (P2 at this age) for the different conditions on the symmetrical left and right clusters. The main difference between groups was a {\textbackslash}textasciitildeþinspace60ms delay in typical infants relative to AgCC, for the ipsilateral response (i.e. left hemisphere) to babbling noise presented in the left ear, whereas no difference was observed in the case of right-ear stimulation. We suggest that our results highlight an asymmetrical callosal connectivity favoring the right-to-left hemisphere direction in typical infants. This asymmetry, similar to recent descriptions in adults, might contribute to an enhancement of left lateralization for language processing beyond the initial cortical left-hemisphere advantage. |
| Abstract: | On some level, human sentence comprehension must involve both memory retrieval and structural composition. This study differentiates these two processes using neuroimaging data collected during naturalistic listening. Retrieval is formalized in terms of "multiword expressions" while structure-building is formalized in terms of bottom-up parsing. The results most strongly implicate Anterior Temporal regions for structure-building and Precuneus Cortex for memory retrieval. |
| Abstract: | Understanding events requires interplaying cognitive processes arising in neural networks whose organisation and connectivity remain subjects of controversy in humans. In the present study, by combining diffusion tensor im- aging and functional interaction analysis, we aim to provide new insights on the organisation of the structural and functional pathways connecting the multiple nodes of the identified semantic system -shared by vision and language (Jouen et al., 2015). We investigated a group of 19 healthy human subjects during experimental tasks of reading sentences or seeing pictures. The structural connectivity was realised by deterministic tractography using an algorithm to extract white matter fibers terminating in the selected regions of interest (ROIs) and the func- tional connectivity by independent component analysis to measure correlated activities among these ROIs. The major connections link ventral neural stuctures including the parietal and temporal cortices through inferior and middle longitudinal fasciculi, the retrosplenial and parahippocampal cortices through the cingulate bundle, and the temporal and prefrontal structures through the uncinate fasciculus. The imageability score provided when the subject was reading a sentence was significantly correlated with the factor of anisotropy of the left parieto- temporal connections of the middle longitudinal fasciculus. A large part of this ventrally localised structural connectivity corresponds to functional interactions between the main parietal, temporal and frontal nodes. More precisely, the strong coactivation both in the anterior temporal pole and in the region of the temporo-parietal cortex suggests dual and cooperating roles for these areas within the semantic system. These findings are dis- cussed in terms of two semantics-related sub-systems responsible for conceptual representation. |
| Abstract: | Self-initiated movements are reliably preceded by a gradual build |