Representation of braille characters in human nerve fibres.

We have used microneurographic techniques in human subjects to record mechanoreceptive afferent responses to standard Braille characters scanned across the finger pads. Responses from all four mechanoreceptor classes (FA I, FA II, SA I and SA II) have been reconstructed to form two-dimensional Spatial Event Plots (raster plots) of the Braille alphabet. Both the SA I and FA I responses resolve the dot patterns of Braille characters with sufficient fidelity that the representations of the individual characters can be recognized visually. Responses from SA II and FA II afferents do not resolve the Braille characters. We believe that the Spatial Event Plots derived from SA I and FA I responses closely approximate the images that are transmitted within a human nerve during Braille reading.