# Shared early processing of distinct tactile features

## TL;DR

The study shows that different tactile sensations like distance, roughness, and curvature share early brain processing, leading to cross-sensory effects.

## Contribution

The research reveals shared early cortical processing for tactile distance, roughness, and curvature through cross-property adaptation aftereffects.

## Key findings

- Adapting to tactile distance affects perception of roughness and curvature.
- Cross-property aftereffects suggest shared neural mechanisms in early somatosensory processing.
- Bidirectional effects indicate a common initial processing stage for spatial tactile properties.

## Abstract

The extent to which spatial tactile properties share neural pathways remains unclear, yet it is the key to understanding how the brain constructs coherent object representations from distributed spatial inputs. One basic spatial property is the perceived tactile distance between two simultaneous touches on the skin. It exhibits adaptation aftereffects: when body areas are repeatedly touched at two points, subsequently presented smaller distances are perceived as smaller than on unadapted areas. We investigated whether tactile distance adaptation influences the perception of other spatial properties, macro-scale roughness and curvature, indicating shared neural mechanisms. In experiment 1, adapting the skin to a fixed tactile distance reduced perceived roughness of subsequent gratings with smaller groove widths, as assessed through passive touch at the finger pad. This aftereffect likely originates from early cortical processing, as it is orientation-specific and independent of peripheral receptor desensitization. Experiment 2 demonstrated that curvature perception increases after adaptation to a two-point distance larger than the curve, suggesting overlap in processing pathways. Experiment 3 further supported early processing involvement, as the distance-to-roughness aftereffect did not transfer to adjacent skin regions of the same finger. Experiment 4 revealed bidirectional aftereffects: roughness adaptation also influenced distance perception. However, within-property aftereffects were stronger than cross-property effects. By revealing the existence of cross-property adaptation aftereffects with low-level characteristics, our findings provide evidence that tactile distance, roughness, and curvature share early somatosensory processing. This suggests that spatially defined properties undergo a common initial processing stage, sharing initial steps rather than existing in a hierarchical processing arrangement.

•Tactile distance, roughness, and curvature show overlaps in their somatosensory processing•Adapting to one tactile property produced measurable aftereffects in another•Findings likely indicate a shared early cortical basis for spatial tactile properties

Tactile distance, roughness, and curvature show overlaps in their somatosensory processing

Adapting to one tactile property produced measurable aftereffects in another

Findings likely indicate a shared early cortical basis for spatial tactile properties

Health sciences