Myeloarchitectonic Asymmetries of Language Regions in the Human Brain

Abstract

One prominent theory in neuroscience and psychology assumes that cortical regions for language are left hemisphere lateralized in the human brain. In the current study, we used a novel technique, quantitative magnetic resonance imaging (qMRI), to examine interhemispheric asymmetries in language regions in terms of macromolecular tissue volume (MTV) and quantitative longitudinal relaxation time (T1) maps in the living human brain. These two measures are known to reflect cortical myeloarchitecture from the microstructural perspective. One hundred and fifteen adults (55 male, 60 female) were examined for their myeloarchitectonic asymmetries of language regions. We found that the cortical myeloarchitecture of inferior frontal areas including the pars opercularis, pars triangularis, and pars orbitalis is left lateralized, while that of the middle temporal gyrus, Heschl’s gyrus, and planum temporale is right lateralized. Moreover, the leftward lateralization of myelination structure is significantly correlated with language skills measured by phonemic and speech tone awareness. This study reveals for the first time a mixed pattern of myeloarchitectonic asymmetries, which calls for a general theory to accommodate the full complexity of principles underlying human hemispheric specialization.

Microstructural asymmetries of the planum temporale predict functional lateralization of auditory-language processing

“…As one of the most prominent structural asymmetries across the entire human brain, PT structural asymmetries have been well recognized and widely believed to play a critical role in human auditory or language processing 8, 19,21,30,[43][44][45] . In concordance, anomalies of PT asymmetries in surface area or thickness have been reported in various brain disorders with auditory or language de cits, e.g., dyslexia, autism, and schizophrenia 17,21, 46-52 .…”

A Whole-Brain 3D Myeloarchitectonic Atlas: Mapping the Vogt-Vogt Legacy to the Cortical Surface

“…Notably, recent developments in advanced imaging sequences, such as myelin water imaging (van der Weijden et al, 2020) or high-field laminar fMRI (Trampel et al, 2019), allow for an increasingly detailed study of cortical myelin contents. In this regard, our histology-validated depth profiles can be harnessed as ground-truth data to validate future in vivo imaging studies investigating myeloarchitecture (O’Muircheartaigh et al, 2019; Yuan et al, 2021).…”

“…Additionally, our digital atlas does not contain information on potential left-right asymmetries, since the original sources also do not contain any lateralization information. Nevertheless, a recent quantitative MRI study investigating myeloarchitectural metrics of the language system revealed heterogenous lateralization patterns (Yuan et al, 2021): While inferior frontal areas were left lateralized, the middle and superior temporal gyrus (Heschl’s gyrus and planum temporale) was found to be right lateralized. As such, future research should therefore be directed at potential functional implications of myeloarchitectural lateralization patterns in larger cohorts.…”

Are We Right about the Right TPJ? A Review of Brain Stimulation and Social Cognition in the Right Temporal Parietal Junction

“…While there are debates among the definitions, we defer to a broader (i.e., greater area) inclusionary definition. There are asymmetrical anatomical differences (i.e., hemispheric), one of the most notable is the planum temporale, in which we and others have discovered significant structural lateralized differences [31][32][33][34][35][36][37], which lead to significant functional differences in non-social domains [38][39][40]. For example, lesions of the lTPJ (left TPJ) typically lead to aphasias and verbal language disruption [41], visual-spatial neglect, however, is a common outcome of rTPJ damage [42,43].…”