Language aptitude is related to the anatomy of the transverse temporal gyri

Why is it that some people seem to learn new languages faster and more easily than others? The present study investigates the neuroanatomical basis of language learning aptitude, with a focus on the multiplication pattern of the transverse temporal gyrus/gyri (TTG/TTGs) of the auditory cortex. The size and multiplication pattern of the first TTG (i.e., Heschl's gyrus; HG) and of additional posterior TTGs, when present, are highly variable both between brain hemispheres and individuals. Previous work has shown the multiplication pattern of the TTGs to be related to musical and linguistic abilities. Specifically, one study found that high language learning aptitude correlated with more TTGs in the right hemisphere, even though language functions are generally left-lateralized. In this study, we used the recently developed TASH (Toolbox for the Automated Segmentation of Heschl's Gyrus) and MCAI (Multivariate Concavity Amplitude Index) toolboxes to automatically extract structural (e.g., cortical volume, surface area, thickness) and multiplication pattern measures of the TTGs from 82 MRI scans, and related them to participants' language aptitude scores. In contrast to previous results, we found that higher language aptitude was related to fewer TTGs in the right hemisphere and to greater surface area of the first right TTG and of the second left TTG. Furthermore, more languages learned in life were associated with higher language learning aptitude, opening up questions about the structure-function relationship of the TTGs and language learning, and about how language aptitude and language learning are related.