Perceptual and decisional attenuation of tactile perception during the preparation of self- versus externally-generated movements.

We investigated tactile perception during the execution of self- versus externally-generated movements. In a first experiment, we established the temporal characteristics of the movements of interest. In a second experiment, participants had to try to detect a short gap in an otherwise continuous vibratory stimulus delivered to their right wrist under conditions of rest, throwing (i.e., self-initiated movement), or catching a basketball (i.e., externally-generated movement). Our hypothesis was that different patterns of tactile sensitivity (d') and response bias (criteria c and c') would be observed as a function of the timing of gap delivery (i.e., during movement preparation or movement execution) and the type of movement (self- or externally-generated). A third experiment investigated tactile perception at rest while participants adopted different hand postures. This experiment also tested the simple preparation of the self-/externally-generated movements versus the observation of these targeted movements as performed by the experimenter. Due to sensory suppression, participants were significantly less sensitive in detecting the gap in tactile stimulation while executing the movement. Preparing to catch the ball only triggered a shift in response bias (i.e., participants were more liberal/conservative when reporting the gap in stimulation), but no change in perceptual sensitivity was observed, as compared to rest. Preparing to make a ball-throwing movement resulted in a significant decrement in tactile sensitivity, as well as a shift in participants' criterion toward their being more conservative, when responding to the presence of the target. Similar decrements were observed for the observation of self-initiated movement preparation, but not for the observation of their externally-generated counterparts. Taken together, these results demonstrate that different forms of attenuation influence tactile perception, depending on the type of movement that is executed: perceptual and decisional attenuation for self-initiated movements, but only decisional attenuation for externally-generated movements. These results suggest that the movement preparation sensorimotor contingencies are already modulated in prefrontal decision-related cortical brain areas.