Handedness is related to neural mechanisms underlying hemispheric lateralization of face processing.

Stefan Frässle,Sören Krach,Andreas Jansen,Frieder Michel Paulus

doi:10.1038/srep27153

Abstract

While the right-hemispheric lateralization of the face perception network is well established, recent evidence suggests that handedness affects the cerebral lateralization of face processing at the hierarchical level of the fusiform face area (FFA). However, the neural mechanisms underlying differential hemispheric lateralization of face perception in right- and left-handers are largely unknown. Using dynamic causal modeling (DCM) for fMRI, we aimed to unravel the putative processes that mediate handedness-related differences by investigating the effective connectivity in the bilateral core face perception network. Our results reveal an enhanced recruitment of the left FFA in left-handers compared to right-handers, as evidenced by more pronounced face-specific modulatory influences on both intra- and interhemispheric connections. As structural and physiological correlates of handedness-related differences in face processing, right- and left-handers varied with regard to their gray matter volume in the left fusiform gyrus and their pupil responses to face stimuli. Overall, these results describe how handedness is related to the lateralization of the core face perception network, and point to different neural mechanisms underlying face processing in right- and left-handers. In a wider context, this demonstrates the entanglement of structurally and functionally remote brain networks, suggesting a broader underlying process regulating brain lateralization.

Highlights

Willems et al demonstrated that the lateralization of the fusiform face area (FFA)[6] depends on handedness: While the FFA was lateralized to the right hemisphere in right-handers, such asymmetric hemispheric lateralization was absent in left-handers[17]
We asked whether differences in the functional organization of the core face perception network manifest in other modalities, in the gray matter volume and in physiological measures of cognitive processing
We adopted a recent effective connectivity approach to investigate how handedness relates to hemispheric lateralization during face processing

Summary

Introduction

From neuroimaging studies that test measures of functional activation, it remains unknown whether differences in the recruitment of bilateral FFA in left-handers manifest in the intra- or interhemispheric integration of the network, or both, and whether the observed differences arise from influences at early or late stages within the processing hierarchy of the core face perception network. Delineating these mechanisms yields deeper insights into the lateralized processes in the face perception network, and could advance our understanding of the pathophysiology of diseases in which face processing is impaired (e.g., prosopagnosia). Implementing such a multimodal approach, combing DCM, structural MRI and pupillometry, we attempted to more closely delineate the nature of differential neural mechanisms underlying face processing in right- and left-handers

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Conclusion