Abstract
The visual word form area (VWFA) is an experience-dependent region in left ventral temporal cortex that responds to written words over other visually similar stimuli, e.g. objects and faces. In adults, the VWFA is thought to connect with the amodal high-level language network (comprised of six regions spanning frontal and temporal cortex). Does the word-selectivity of the VWFA emerge from a pre-existing bias to linguistic stimuli? Does the selectivity and laterality of the language network change with reading as connected components (i.e. VWFA) gain word-selectivity? To answer these questions, we scanned young children (N=34; 4-8 years of age) and adults (N=35; 18-45 years of age) while they listened to blocks of meaningful English sentences, Nonsense sentences, and texturized speech. A subset of participants also completed a high-level visual localizer (blocks of words, scrambled words, line drawings of objects, faces). Functional regions of interest (fROIs) per subject were defined using one run (English > Nonsense and Words > Objects for language and VWFA fROIs respectively). We used independent run data to calculate percent signal change and a selectivity index reflecting each fROI’s selectivity to either auditory language or visual words. Even the youngest children (<6 years) showed greater selectivity to visual words over language in both the left and right VWFA. The selectivity of the language network to English sentences did not change with reading ability (with selective and lateralized temporal fROIs at age 4). However, selectivity of the frontal language fROIs increased in left dominance along with increasing left VWFA dominance in word-selectivity. These results suggest that 1) VWFA word-selectivity does not emerge from pre-reading selectivity to general linguistic input; 2) VWFA word-selectivity and laterality emerges in tandem with the emergence of linguistic selectivity of the left frontal language fROIs as a child learns to read.