Abstract

Research has suggested that altering the perceived
shape and size of the body image significantly
affects perception of somatic events. The current study
investigated how multisensory illusions applied to the body
altered tactile perception using the somatic signal detection
task. Thirty-one healthy volunteers were asked to report the
presence or absence of near-threshold tactile stimuli delivered
to the index finger under three multisensory illusion
conditions: stretched finger, shrunken finger and detached
finger, as well as a veridical baseline condition. Both
stretching and shrinking the stimulated finger enhanced
correct touch detections; however, the mechanisms underlying
this increase were found to be different. In contrast,
the detached appearance reduced false touch reports—possibly
due to reduced tactile noise, as a result of attention
being directed to the tip of the finger only. These findings
suggest that distorted representations of the body could
have different modulatory effects on attention to touch and
provide a link between perceived body representation and
somatosensory decision-making.