Structure and function of word laterality in early childhood.

Abstract

Many of the brain's functional regions display lateralization, meaning they are more specialized to one hemisphere than the other. The visual word form area (VWFA) is one such region; its specialization for written scripts, which develops only after literacy, is consistently dominant on the left in adults. The experience-dependent nature of the VWFA makes it a prime opportunity to investigate the development of functional laterality in the human brain. Therefore, we ask, "What neural correlates relate to the development of word laterality in children?" We tested two potential sources of this word laterality: (a) structural connectivity (s-connectivity) of the VWFA with the high-level language network in frontal and temporal cortices and (b) activation in these language regions. To do so, we scanned reading children (4-13 years) on a visual functional magnetic resonance imaging localizer to define the VWFA and its word selectivity and a separate auditory functional magnetic resonance imaging localizer to define language regions and their linguistic selectivity, and we collected diffusion-weighted imaging to examine white matter connectivity. Probabilistic tractography was used to quantify white matter connections between our subject-specific functional regions. VWFA word laterality was predicted by the positive interaction between laterality of s-connectivity to temporal language regions and laterality of temporal language regions' selectivity, suggesting that the VWFA tends to be more left-lateralized when both temporal language areas are left-lateralized and the VWFA has strong s-connectivity to that left-lateralized language network. More generally, our findings suggest that both s-connectivity to related regions and activation patterns in those connected regions may play a role in the development of functional laterality, and shed light on the development of the neural circuitry that underlies reading. (PsycInfo Database Record (c) 2026 APA, all rights reserved).