The influence of expectation in sensory attenuation

Sensory Attenuation (SA) refers to the phenomenon that self-generated stimuli are perceived less intensely than externally generated sensations. Recent findings, however, suggest that SA is a phenomenon mostly linked to prediction rather than intentional actions. With the present study, we aimed at interrogating this question.The study consisted of a VR setup and a simultaneous EEG recording. Participants were required to either actively touch or passively get touched by a virtual ball that gave them (or not) an electrical stimulation at the finger, in a probabilistic manner. Participants had to learn the probability to receive a stimulation within a sequence. Through this paradigm we were able to compare actively generated to passively perceived stimulations while controlling for predictability effects. We analysed EEG data at ball touch using a univariate general linear model approach.Late SEPs (P200-300) were found to be significantly affected by movement and by the expectation of touch. ERP amplitudes generated by the electrical stimulation was reduced in conditions in which participants (i) actively moved and (ii) learned that the stimulation was more likely. We also found a parametric effect showing that the suppression associated to the movement condition was linearly modulated by the expectation of touch.Our results confirm the existence of SA and, at the same time, show the presence of an attenuation effect for predicted stimuli, which linearly sums on the attenuation generated by active movements. These results shed new light on the mechanisms underpinning SA and its neurophysiological correlates.