Functional relevance of the extrastriate body area for visual and haptic object recognition: a preregistered fMRI-guided TMS study.

The extrastriate body area (EBA) is a region in the lateral occipito-temporal cortex (LOTC), which is sensitive to perceived body parts. Neuroimaging studies suggested that EBA is related to body and tool processing, regardless of the sensory modalities. However, how essential this region is for visual tool processing and nonvisual object processing remains a matter of controversy. In this preregistered fMRI-guided repetitive transcranial magnetic stimulation (rTMS) study, we examined the causal involvement of EBA in multisensory body and tool recognition. Participants used either vision or haptics to identify 3 object categories: hands, teapots (tools), and cars (control objects). Continuous theta-burst stimulation (cTBS) was applied over left EBA, right EBA, or vertex (control site). Performance for visually perceived hands and teapots (relative to cars) was more strongly disrupted by cTBS over left EBA than over the vertex, whereas no such object-specific effect was observed in haptics. The simulation of the induced electric fields confirmed that the cTBS affected regions including EBA. These results indicate that the LOTC is functionally relevant for visual hand and tool processing, whereas the rTMS over EBA may differently affect object recognition between the 2 sensory modalities.

Structural neuroplasticity of the superior temporal plane in early and late blindness.

Blindness is associated with well-documented changes to the morphometry and function of the occipital cortex. By comparison, its impact on the perisylvian regions in the superior temporal plane (STP) is poorly understood, with many studies reporting null findings on this issue. Here we re-approach this question using a morphometric analysis that relied on fine-scale, manual annotation of 13 sub-regions within the STP and that quantified both univariate and multivariate differences in morphometry. We applied these analyses to both cortical thickness (CT) and surface area (SA) data from congenitally and late blind, as compared to two matched sighted control groups. The univariate analyses indicated that for CT, no region differentiated blind from sighted, and for SA, two regions showed lower values for congenitally blind. Moreover, the multivariate analyses identified more robust signatures of plasticity in blindness. Specifically, pairwise regional correlations of CT values between contralateral regions were significantly higher for both blind groups as compared to sighted controls. A similar pattern for SA data was found for congenitally blind alone. Our findings indicate that blindness strongly impacts STP, resulting in a more coordinated pattern of interhemispheric morphometric development. We discuss implications for theories of language plasticity and models of neuroplasticity in the blind.

Congenital blindness is associated with large-scale reorganization of anatomical networks.

Blindness is a unique model for understanding the role of experience in the development of the brain's functional and anatomical architecture. Documenting changes in the structure of anatomical networks for this population would substantiate the notion that the brain's core network-level organization may undergo neuroplasticity as a result of life-long experience. To examine this issue, we compared whole-brain networks of regional cortical-thickness covariance in early blind and matched sighted individuals. This covariance is thought to reflect signatures of integration between systems involved in similar perceptual/cognitive functions. Using graph-theoretic metrics, we identified a unique mode of anatomical reorganization in the blind that differed from that found for sighted. This was seen in that network partition structures derived from subgroups of blind were more similar to each other than they were to partitions derived from sighted. Notably, after deriving network partitions, we found that language and visual regions tended to reside within separate modules in sighted but showed a pattern of merging into shared modules in the blind. Our study demonstrates that early visual deprivation triggers a systematic large-scale reorganization of whole-brain cortical-thickness networks, suggesting changes in how occipital regions interface with other functional networks in the congenitally blind.