Connectional asymmetry of the inferior parietal lobule shapes hemispheric specialization in humans, chimpanzees, and rhesus macaques.

Luqi Cheng,Lingzhong Fan,Gaolang Gong,Tianzi Jiang,Jiaojian Wang,Gang Li,Chet Sherwood,Yuanchao Zhang

doi:10.7554/elife.67600

Abstract

The inferior parietal lobule (IPL) is one of the most expanded cortical regions in humans relative to other primates. It is also among the most structurally and functionally asymmetric regions in the human cerebral cortex. Whether the structural and connectional asymmetries of IPL subdivisions differ across primate species and how this relates to functional asymmetries remain unclear. We identified IPL subregions that exhibited positive allometric in both hemispheres, scaling across rhesus macaque monkeys, chimpanzees, and humans. The patterns of IPL subregions asymmetry were similar in chimpanzees and humans, but no IPL asymmetries were evident in macaques. Among the comparative sample of primates, humans showed the most widespread asymmetric connections in the frontal, parietal, and temporal cortices, constituting leftward asymmetric networks that may provide an anatomical basis for language and tool use. Unique human asymmetric connectivity between the IPL and primary motor cortex might be related to handedness. These findings suggest that structural and connectional asymmetries may underlie hemispheric specialization of the human brain.

Highlights

The association cortex has expanded greatly in size and exhibits modified connectivity patterns in human brain evolution (Orban et al, 2006; Mars et al, 2017; Ardesch et al, 2019; Van Essen et al, 2019)
A data-driven connectivity-based parcellation was applied to group the vertices in the inferior parietal lobule (IPL) into functionally distinct clusters based on anatomical connectivity (Figure 1)
We identified the optimal number of subregions of the IPL by choosing the maximum number of subregions that showed a coherent topological organization across all species while balancing that by the minimum number of subregions that could be identified based on their cytoarchitectural definitions in macaques, chimpanzees, and humans (Pandya and Seltzer, 1982; Reyes, 2017)

Summary

Introduction

The association cortex has expanded greatly in size and exhibits modified connectivity patterns in human brain evolution (Orban et al, 2006; Mars et al, 2017; Ardesch et al, 2019; Van Essen et al, 2019). Evolutionary Biology Neuroscience of the neocortex in human brains (Orban et al, 2006; Van Essen and Dierker, 2007; Donahue et al, 2018). Functional and neuroanatomical asymmetries are pronounced in the human brain, appearing to be more extreme compared with other primate species, especially in the association cortex (Chance and Crow, 2007). Comparative studies on brain asymmetry are crucial for understanding the evolution and function of the modern human brain

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