Résumé
The ability to detect tactile sensation is suppressed in a moving limb; however, the underlying mechanism for this effect is debated. A forward model explanation suggests that predictive processes attenuate peripheral sensation to better detect the limb’s future sensory state. Alternatively, a backward masking account asserts that reafferent feedback masks weaker stimuli, making them harder to detect. To investigate whether a motor plan must be executed to induce suppression, the present study employed a tactile detection task during a stop-signal reaction time paradigm. On stop trials, although a forward model is generated, the planned movement can be inhibited/cancelled given sufficient time. It was hypothesized that if tactile suppression is related to generation of the forward model, then suppression would be observed regardless of whether the movement was initiated or inhibited. Participants reacted to a visual go-signal by making a rapid wrist extension, but on 25% of trials a stop-signal was presented at a delay resulting in a 50% probability of successfully inhibiting the response. A near-threshold tactile stimulus was applied to the dorsum of the hand on each trial from 100 ms before to 100 ms after predicted movement onset, and participants were asked whether the stimulus was detected. Results showed that tactile suppression did not occur when the movement was successfully inhibited, even though a forward model was presumably generated. In contrast, suppression was present when the movement was executed on both go- and stop-trials. Collectively, these results are consistent with a backward masking account of tactile suppression.
