Abstract
Functional networks are reorganized in blind individuals to engage typically visual cortical sensory areas in nonvisual tasks. Braille has served as a major model to investigate such crossmodal plasticity, but the underlying brain representations and spatiotemporal dynamics of these computations remain poorly understood. Here, we presented individual visual and tactile (braille) alphabetic letters to sighted and early-blind participants, respectively, while recording brain activity with magnetoencephalography (MEG). Both groups of participants read letters passively, responding via button press to occasional vigilance targets. For each group, we used multivariate pattern analysis to compare brain responses to alphabetical letters across different anatomical locations and time points in the trial epoch. Next, we modeled low-level stimulus representations in tactile and visual brain responses, as well as higher-level distributional statistics of letter occurrences in a text corpus. Using these representational similarity models and a shared-variance approach, we examined the spatiotemporal dynamics of the representational cascade, identifying a convergence from distinct low-level to shared higher-level representations of individual letter stimuli between early sensory and left fusiform regions. Taken together, the results reveal spatiotemporally dissociable representations of individual letter processing, common and distinct computations in blind and sighted individuals, and a possible role for early “visual” cortex in the reorganized functional brain networks of blind readers.