Nathalie Tzourio-Mazoyer's research while affiliated with French National Centre for Scientific Research and other places

The cortical ribbon changes throughout a person's lifespan, with the most significant changes occurring during crucial development and aging periods. Changes during adulthood are rarely investigated due to the scarcity of neuroimaging data during this period. After one factor of this thinning process is intense ongoing intracortical myelination (MYEL). Here, we report age-related changes in CT, MYEL, and their ratio in 447 participants aged 18 to 57 years (BIL&GIN cohort). We propose the CT/MYEL ratio to be a multimodal cortical maturation index (MATUR) capable of reflecting 1) stages during which CT and MYEL patterns diverge and 2) the regional differences in cortical maturation that occur in adulthood. Age mainly decreased CT in all cortical regions, with larger reductions occurring in the bilateral insular lobes, temporal and frontal poles, and cingulate cortices. Age led to a linear increase in MYEL in the entire cortex and larger increases in the primary motor, auditory, and visual cortices. The effects of age on the MATUR index were characterized by both linear and quadratic components. The linear component mimicked the pattern found in CT, with 1) a robust amplification of the global and regional effects of age on CT and 2) evidence of new bilateral linear decreases in the frontal and cortical cortices. Most importantly, age exhibited additional large quadratic effects on the MATUR index in the bilateral frontal (more prominent in the right hemisphere), parietal, temporal, and cingulate regions that were not highlighted by the CT metric. Thus, the MATUR index was more sensitive to age-related cortical structural changes during adulthood than was either CT or MYEL alone. As evidenced by the large quadratic component of the effect of age, the newly proposed maturation index dramatically improved the characterization of the regional cortical territories, uncovering the latest brain maturation steps that occur before stabilization and deterioration occur in mid- and late adulthood.

We have identified the brain areas involved in Manual Preference (MP) in 143 left-handers (LH) and 144 right-handers (RH). First, we selected the pairs of homotopic regions of interest (hROIs) of the AICHA atlas with significant contralateral activation and asymmetry during the right hand and the left hand Finger-Tapping (FT) both in RH and LH. Thirteen hROIs were selected, including the primary and secondary sensorimotor and premotor cortices, thalamus, dorsal putamen, and cerebellar lobule IV. In both groups, contralateral activations and ipsilateral deactivations were seen, with stronger asymmetries when the preferred hand was used. Comparing with different models for the prediction of MP, we found that the differences in activity during preferred hand minus non-preferred hand movement in 11 contralateral and/or ipsilateral hROIS were best at explaining handedness distribution. Two different mechanisms were identified: 1. Stronger contralateral activity of cortical and cerebellar motor areas during right hand movement, seen in both groups but modulated by handedness; 2. Stronger deactivation in ipsilateral areas during dominant hand movement in both groups, LH here mirroring RH. The present study thus demonstrates that handedness neural support is complex and not simply based on a mirrored organization of hand motor areas.

Based on the joint investigation in 287 healthy volunteers (150 left-Handers (LH)) of language task-induced asymmetries and intrinsic connectivity strength of the sentence-processing supramodal network, we show that individuals with atypical rightward language lateralization (N = 30, 25 LH) do not rely on an organization that simply mirrors that of typical leftward lateralized individuals. Actually, the resting-state organization in the atypicals showed that their sentence processing was underpinned by left and right networks both wired for language processing and highly interacting by strong interhemispheric intrinsic connectivity and larger corpus callosum volume. Such a loose hemispheric specialization for language permits the hosting of language in either the left and/or right hemisphere as assessed by a very high incidence of dissociations across various language task-induced asymmetries in this group.

Based on the joint investigation in 287 healthy volunteers (150 left-Handers (LH)) of language task-induced asymmetries and intrinsic connectivity strength of the sentence-processing supramodal network, we show that individuals with atypical rightward language lateralization (N = 30, 25 LH) do not rely on an organization that simply mirrors that of typical leftward lateralized individuals. Actually, the resting-state organization in the atypicals showed that their sentence processing was underpinned by left and right networks both wired for language processing and highly interacting by strong interhemispheric intrinsic connectivity and larger corpus callosum volume. Such a loose hemispheric specialization for language permits the hosting of language in either the left and/or right hemisphere as assessed by a very high incidence of dissociations across various language task-induced asymmetries in this group.

Based on the joint investigation in 287 healthy volunteers (150 Left-Handers (LH)) of language task-induced asymmetries and intrinsic connectivity strength of the sentence-processing supramodal network, we show that individuals with atypical rightward language lateralization (N = 30, 25 LH) do not rely on an organization that simply mirrors that of typical leftward lateralized individuals. Actually, the resting-state organization in the atypicals showed that their sentence processing was underpinned by left and right networks both wired for language processing and highly interacting by strong interhemispheric intrinsic connectivity and larger corpus callosum volume. Such a loose hemispheric specialization for language permits the hosting of language in either the left and/or right hemisphere as assessed by a very high incidence of dissociations across various language task-induced asymmetries in this group.

A bstract We have identified the brain areas involved in Manual Preference (MP) in 143 left-handers (LH) and 144 right-handers (RH)). First, we selected the pairs of homotopic regions of interest (hROIs) of the AICHA atlas with significant contralateral activation and asymmetry during the right-hand and the left-hand Finger-Tapping (FT) both in RH and LH. Thirteen hROIs were selected, including the primary and secondary sensorimotor, and premotor cortices, thalamus, dorsal putamen and cerebellar lobule IV. Both contralateral activations and ipsilateral deactivations (reversed for the cerebellum) were seen in primary motor and somatosensory areas, with stronger asymmetries when the preferred hand was used. Comparing the prediction of MP with different combinations of BOLD variations in these 13 hROIs, the differences between movement of the preferred hand versus that of the non-preferred hand within the contralateral and/or ipsilateral cortices of 11 hROIS performed best at explaining handedness distribution, Handedness is thus supported by: 1-between-hand variations of ipsilateral deactivations of hand primary sensorimotor and secondary somatosensory cortices and 2-variations in regions showing the same profile in left and right-handers during the right or left FT. The present study demonstrates that right and left-handedness are not based on mirrored organization of hand control areas.

We report on MRi-Share, a multi-modal brain MRI database acquired in a unique sample of 1,870 young healthy adults, aged 18 to 35 years, while undergoing university-level education. MRi-Share contains structural (T1 and FLAIR), diffusion (multispectral), susceptibility weighted (SWI), and resting-state functional imaging modalities. Here, we described the contents of these different neuroimaging datasets and the processing pipelines used to derive brain phenotypes, as well as how quality control was assessed. In addition, we present preliminary results on associations of some of these brain image-derived phenotypes at the whole brain level with both age and sex, in the subsample of 1,722 individuals aged less than 26 years. We demonstrate that the post-adolescence period is characterized by changes in both structural and microstructural brain phenotypes. Grey matter cortical thickness, surface area and volume were found to decrease with age, while white matter volume shows increase. Diffusivity, either radial or axial, was found to robustly decrease with age whereas fractional anisotropy only slightly increased. As for the neurite orientation dispersion and densities, both were found to increase with age. The isotropic volume fraction also showed a slight increase with age. These preliminary findings emphasize the complexity of changes in brain structure and function occurring in this critical period at the interface of late maturation and early aging.

We applied a multitask multimodal hierarchical classification (MMHC) to 287 volunteers (150 left-handers) to establish different brain language hemispheric dominance patterns (LangDom). MMHC was based on inter- and intrahemispheric measures of the sentence core network (SENT_CORE): 1) task-induced asymmetries (ACTIV) while listening to, reading, and producing sentences compared to word lists; 2) resting-state degree connectivity (Rs_DC) and asymmetry; and 3) interhemispheric connectivity (Rs_mIHHC). Three LangDom were found, including two typical groups, one with higher (N=125) leftward ACTIV and Rs_DC asymmetries and lower Rs_mIHHC than the other (N=132). The third was an atypical group (ATYP, N=30, 25 left-handers), having rightward ACTIV during the 3 language tasks but high Rs_DC in both hemispheres and high Rs_mIHHC. ATYP LangDom relies on a left SENT_CORE wired for language by default with strong interhemispheric connections with their right SENT_CORE. This loose specialization was associated with 40% of dissociations, decreased anatomical asymmetries, and lower verbal memory.

A pivotal question in modern neuroscience is which genes regulate brain circuits that underlie cognitive functions. However, the field is still in its infancy. Here we report an integrated investigation of the high-level language network (i.e., sentence processing network) in the human cerebral cortex, combining regional gene expression profiles, task fMRI, large-scale neuroimaging meta-analysis, and resting-state functional network approaches. We revealed reliable gene expression-functional network correlations using three different network definition strategies, and identified a consensus set of genes related to connectivity within the sentence-processing network. The genes involved showed enrichment for neural development and actin-related functions, as well as association signals with autism, which can involve disrupted language functioning. Our findings help elucidate the molecular basis of the brain’s infrastructure for language. The integrative approach described here will be useful to study other complex cognitive traits.