Index finger somatosensory evoked potentials in blind Braille readers

Traditionally, vision has been considered the dominant modality in our multi-sensory perception of the surrounding world. Sensory input via non-visual tracts becomes of greater behavioural relevance in totally blind individuals to enable effective interaction with the world around them. These include audition and tactile perceptions, leading to an augmentation in these perceptions when compared with normal sighted individuals. The objective of the present work was to study the index finger somatosensory evoked potentials (SEPs) in totally blind and normal sighted individuals.

SEPs were recorded in 15 Braille reading totally blind females and compared with 15 age-matched normal sighted females. Latency and amplitudes of somatosensory evoked potential waveforms (N9, N13, and N20) were measured.

Amplitude of N20 SEP (a cortical somatosensory evoked potential) was significantly larger in the totally blind than in normal sighted individuals (p < 0.05). The amplitudes of N9 and N13 SEP and the latencies of all recorded SEPs showed no significant differences.

Blindness has a profound effect on the Braille reading right index finger. Totally blind Braille readers have larger N20 amplitude, suggestive of greater somatosensory cortical representation of the Braille reading index finger.