The Cortical Network for Braille Writing in the Blind

Introduction: Traditionally, multisensory interactions have been studied primarily at the level of ‘sensory modalities’. Conversely, fundamental forms of high-order cognition, such as reading and writing, are usually studied in the context of one modality - vision. People without sight, however, use the kinesthetic-based Braille writing, and haptic-based Braille reading. We asked how modality-specific - or supramodal - are the cognitive and motor control mechanisms underlying writing and reading through either the non-visual or visual modalities? While a number of previous functional Magnetic Resonance Imaging (fMRI) studies have investigated the brain networks for Braille reading in the blind, such studies on Braille writing are lacking. Consequently, no comparative network analysis of Braille writing vs. reading exists. Here, we report the first study of Braille writing, and a comparison of the brain organization for Braille writing vs reading. Methods: FMRI was conducted in a Siemens 3T Trio scanner. Our custom MRIcompatible drawing/writing tablet was further modified to provide for Braille reading and writing. Each of five paragraphs of novel Braille text describing objects, faces and navigation sequences was read, then reproduced twice by Braille writing from memory, then read a second time (20s/task). Results and Conclusions: During Braille reading, the haptic-sensing of the Braille letters strongly activated not only the early visual area V1 and V2, but more specialized spatial representation areas, such as the classical visual grapheme area and the Exner motor grapheme area. Braille-writing-from-memory, engaged a significantly more extensive network in dorsal motor, somatosensory/kinesthetic,dorsal parietal and prefrontal cortex. However, in contrast to the largely extended V1 activation in drawingfrom-memory in the blind after training (Likova, 2012), Braille writing from memory generated focal activation restricted to the most foveal part of V1, presumably reflecting topographically the focal demands of such a “pin-pricking” task.