Stability of tactile hand space representation following sensory loss

Several studies have shown the presence of significant distortions in tactile perception across different body parts in healthy individuals. These distortions are flexible and perceptual, as revealed by studies that have temporarily altered the visual experience of the body leading to changes in perceived tactile distances. Further, evidence suggests that cortical areas help to mitigate these distortions by rescaling the distorted body representations into an object-centred frame and preserving tactile size constancy. This rescaling implies that the brain possesses a representation of the physical size of the stimulated body part. However, it remains unclear whether long-term visual deprivation could affect tactile size constancy and body distortions. To answer this question, we asked blind and sighted individuals to estimate tactile distances between pairs of touched points delivered on the dorsum of their hands and fingers. The results showed that, regardless of visual experience, both groups of participants showed typical hand distortions, suggesting that even a lack of visual information since birth does not influence the spatial representation of tactile stimulation. On a more theoretical level, these data reveal that tactile size constancy is a stable principle of the system and develops even in the absence of visual input.