Two distinct forms of functional lateralization in the human brain

TLDR

Hemispheric lateralization is believed to enhance brain function, yet quantitative links between regional lateralization and performance have not been established. We identified two distinct forms of functional lateralization—left‑hemisphere regions preferentially interact within themselves, especially in language and fine‑motor areas, whereas right‑hemisphere regions engage more integratively with both hemispheres in visuospatial and attentional tasks—and the degree of lateralization in each system predicts verbal and visuospatial abilities.

Abstract

The hemispheric lateralization of certain faculties in the human brain has long been held to be beneficial for functioning. However, quantitative relationships between the degree of lateralization in particular brain regions and the level of functioning have yet to be established. Here we demonstrate that two distinct forms of functional lateralization are present in the left vs. the right cerebral hemisphere, with the left hemisphere showing a preference to interact more exclusively with itself, particularly for cortical regions involved in language and fine motor coordination. In contrast, right-hemisphere cortical regions involved in visuospatial and attentional processing interact in a more integrative fashion with both hemispheres. The degree of lateralization present in these distinct systems selectively predicted behavioral measures of verbal and visuospatial ability, providing direct evidence that lateralization is associated with enhanced cognitive ability.