The acquisition of literacy results from an effortful learning process that leads to functional changes in several cortical regions. We explored whether learning to read also leads to anatomical changes within the left intrahemispheric white matter pathways that interconnect these regions. Using diffusion tensor imaging tractography, we compared illiterates with ex-illiterates who learned to read during adulthood and literates who learned to read during their childhood. Literacy related to an increase in fractional anisotropy and a decrease in perpendicular diffusivity in the temporo-parietal portion of the left arcuate fasciculus. The microstructure within this pathway correlated with the reading performance and the degree of functional activation within 2 dominant brain regions involved in reading: The Visual Word Form Area in response to letter strings, and the posterior superior temporal cortex in response to spoken language. Thus, the acquisition of literacy is associated with a reinforcement of left temporo-parietal connections whose microstructure predicts overall reading performance and the functional specialization of the Visual Word Form Area. This anatomical magnetic resonance imaging marker may be useful to predict developmental reading disorders.

ABSTRACT-We evaluated neuro-functional changes associated with late acquisition of reading in an illiterate adult who underwent 20 longitudinal functional magnetic resonance imaging (fMRI) scans during 2 years, while the participant progressed from complete illiteracy to a modest level of alphabetical decoding. Initially, the participant did not activate neural circuits for reading when he was exposed to words; gradually, however, he began to present activation in left occipitotemporal cortex, at the visual word form area. This increase was accompanied by a decrease in face responses. Reading-related responses also emerged in language-related areas of the inferior frontal gyrus and temporal lobe. Additional activations in superior parietal lobe, superior frontal gyrus and posterior medial frontal cortex suggested that reading remained dependent on effortful executive attention and working memory processes. Nevertheless, the results indicate that adult plasticity can be sufficient to induce rapid changes in brain responses to written words and faces in an unschooled and illiterate adult.