Abstract
Becoming a proficient reader requires substantial learning over many years. However, it is unknown how learning to read affects development of distributed visual representations across human ventral temporal cortex (VTC). Using fMRI and a data-driven approach, we examined if and how distributed VTC responses to characters (pseudowords and numbers) develop after age 5. Results reveal anatomical- and hemisphere-specific development. With development, distributed responses to words and characters became more distinctive and informative in lateral but not medial VTC, in the left, but not right, hemisphere. While development of voxels with both positive and negative preference to characters affected distributed information, only activity across voxels with positive preference to characters correlated with reading ability. We also tested what developmental changes occur to the gray and white matter, by obtaining in the same participants quantitative MRI and diffusion MRI data. T1 relaxation time from qMRI and mean diffusivity (MD) from dMRI provide independent measurements of microstructural properties. In character-selective regions in lateral VTC, but not in place-selective regions in medial VTC, we found that T1 and MD decreased from age 5 to adulthood, as well as in their adjacent white matter. T1 and MD decreases are consistent with tissue growth and were correlated with the apparent thinning of lateral VTC. These findings suggest the intriguing possibility that regions that show a protracted functional development also have a protracted structural development. Our data have important ramifications for understanding how learning to read affects brain development, and for elucidating neural mechanisms of reading disabilities.