Tractography-based Parcellation of the Human Middle Temporal Gyrus.

Jinping Xu,Tianzi Jiang,Jiaojian Wang,Lingzhong Fan,Qingmao Hu,Wen Zhang,Hai Li

doi:10.1038/srep18883

Abstract

The middle temporal gyrus (MTG) participates in a variety of functions, suggesting the existence of distinct functional subregions. In order to further delineate the functions of this brain area, we parcellated the MTG based on its distinct anatomical connectivity profiles and identified four distinct subregions, including the anterior (aMTG), middle (mMTG), posterior (pMTG), and sulcus (sMTG). Both the anatomical connectivity patterns and the resting-state functional connectivity patterns revealed distinct connectivity profiles for each subregion. The aMTG was primarily involved in the default mode network, sound recognition, and semantic retrieval. The mMTG was predominantly involved in the semantic memory and semantic control networks. The pMTG seems to be a part of the traditional sensory language area. The sMTG appears to be associated with decoding gaze direction and intelligible speech. Interestingly, the functional connectivity with Brodmann’s Area (BA) 40, BA 44, and BA 45 gradually increased from the anterior to the posterior MTG, a finding which indicated functional topographical organization as well as implying that language processing is functionally segregated in the MTG. These proposed subdivisions of the MTG and its functions contribute to understanding the complex functions of the MTG at the subregional level.

Highlights

It has been well established that the functional segregation of the brain can be characterized by its external connectivity patterns[18]
It was found that the middle temporal gyrus (MTG) subregions had its specific anatomical and functional connectivity patterns, and these subregions were involved in different functional networks
In comparison with the myeloarchitecture-based mapping of the temporal cortex[15], the aMTG primarily corresponded to area tmag.d.aif, and the mMTG primarily corresponded to tmag.d.md, whereas the pMTG predominantly corresponded to tmag.d.s and tmag.d.p*

Summary

Introduction

It has been well established that the functional segregation of the brain can be characterized by its external connectivity patterns[18]. Recent advances in diffusion magnetic resonance imaging have made it possible to show inter-regional anatomical connectivity which has been widely used to define the functional subregions of the brain Based on their distinct in vivo connectivity patterns, the thalamus was firstly parcellated into component subregions by Behrens et al.[19]. Many cortical areas, such as cingulated cortex[20], parietal cortex[21,22,23], superior frontal gyrus[24], frontal pole[25], and temporal pole[26], have been parcellated to define the functional subregions These findings have been proved to be consistent with those from cytoarchitecture-based studies. We explored the potential language-related functions in which each subregion participates by comparing the resting-state FCs between each subregion of the MTG and the frontal-parietal language areas with each of the others

Methods

Results

Conclusion