Neural basis of Braille literacy in blind adults and children

PROJECT SUMMARY
The current project examines the neural basis of Braille reading in proficient congenitally blind adults, late blind
readers with varying degrees of proficiency and blind children learning to read, using fMRI and high-density
diffusion imaging (dMRI). These studies of Braille literacy provide insights into human brain plasticity and the
neural basis of culture.
Reading changes the anatomy and function of the human brain. In sighted people, reading experience
enhances anatomical pathways within and across visual and language networks. Sighted readers develop a
‘visual word form area’ (VWFA) in lateral ventral occipito-temporal cortex (lVOT), tuned to letters and words.
Braille offers insights into the mechanisms of cultural recycling by disentangling which aspects of the reading
brain are modality invariant and which are modality specific. The current proposal distinguishes between two
alternative hypotheses. According to the task-based hypothesis, blind readers develop the same neural
mechanisms for reading as the sighted in the lVOT and show similar connectivity changes, because lVOT is
intrinsically predisposed for modality-invariant shape recognition. By contrast, the connectivity-based
hypothesis proposes that connectivity and experience heavily influence reading localization. It therefore
predicts that blind individuals develop tactile word form areas (TWFAs) in parietal regions with strong
connectivity to somatosensory and language networks. It also predicts that Braille literacy enhances
anatomical connectivity of these parietal network.
Aim 1 investigates the neural changes support this expert reading in congenitally blind adults. Proficient
Braille readers can achieve speeds of 200 words per minute and more. What neural changes enable this
ability? In a series of fMRI experiments with congenitally blind proficient readers we use MVPA and fMRI
adaptation to test our hypothesis that proficient blind readers develop ‘tactile word form areas’ TWFAs in
posterior parietal cortex and connected dorsal occipital areas. Aim 2 tests the prediction that individual
differences in the connectivity (dMRI) and functional specialization of parietal areas predicts individual
differences in reading proficiency among congenitally and late blind adults, whereas individual differences in
early visual areas only predict individual differences in the congenitally blind population. Aim 3 tests the key
prediction that TWFA specialization and Braille-reading associated connectivity changes emerge as a result of
literacy by working with congenitally blind children (dMRI and fMRI) longitudinally, as they learn to read.
Uncovering neural markers of successful Braille literacy will test theories of human brain plasticity and facilitate
and inform strategies for enhancing Braille literacy among people who are blind.

Grant Number: 5R01EY033340-04
NIH Institute/Center: NIH
Principal Investigator: Marina Bedny