Evolution of reading and face circuits during the first three years of reading acquisition

Although words and faces activate neighboring regions in the fusiform gyrus, we lack an understanding of how this category selectivity emerges during development. To investigate the organization of reading and face circuits at the earliest stage of reading acquisition, we measured the fMRI responses to words, faces, houses, and checkerboards in three groups of 60 children: 6-year-old pre-readers, 6-year-old beginning readers and 9-year-old advanced readers. The results showed that specific responses to written words were absent prior to reading, but emerged in beginning readers, irrespective of age. Likewise, specific responses to faces were weak or absent in pre-readers, but they emerged more slowly and continued to evolve in the 9-year-olds, primarily driven by age rather than by schooling. Crucially, the sectors of ventral visual cortex that become specialized words and faces harbored their own functional connectivity prior to reading acquisition: the VWFA with left-hemispheric spoken language areas, and the FFA with the contralateral region and the amygdalae. The results support the view that reading acquisition occurs through the recycling of a pre-existing but plastic circuit which, in pre-readers, already connects the VWFA site to other distant language areas. Furthermore, reading acquisition does not compete with the face system directly, through a pruning of preexisting face responses, but indirectly, by partially reorienting the slow growth of face responses to the right hemisphere.