The Tactile Distance Aftereffect Transfers to Roughness Perception.

Touch is susceptible to various aftereffects. Recent findings on tactile distance perception demonstrate that when an area of the body is repeatedly touched at two points separated by a given distance, subsequently presented smaller distances are perceived as smaller and larger distances as larger. Here we investigate whether adaptation to a tactile distance transfers to the perception of coarse textures’ roughness. Additionally, we examine whether this transfer is orientation-specific, which is typical for low-level aftereffects. On each trial, the tip of the left index finger was adapted either 1) to a tactile two-point distance of 4 mm applied along the length of the finger, 2) the same distance applied across the width of the finger or 3) to single indentations. After adaptation to a two-point distance, participants systematically perceived subsequently presented gratings with smaller groove distances as being less rough–-when the orientation of the adapted distance matched that of the texture. This reflects an aftereffect transfer for the orientation-congruent condition only. The results suggest that the processing of distance between two points on the skin is involved in the computation of texture, and that texture is a basic somatosensory feature computed at relatively early stages of sensory processing.