Abstract
Sensory consequences of one’s own action are often perceived as less intense, and lead to reduced neural responses, compared to externally generated stimuli. It has been proposed that such sensory attenuation is due to predictive mechanisms based on the efference copy, which is a copy of the motor command. However, sensory attenuation has also been observed outside the context of voluntary action, namely when stimuli are temporally predictable. Here, we investigated whether attenuation of sensory action consequences is due to action-based predictive mechanisms or rather due to differences in temporal predictability. 25 participants took part in our fMRI study. During fMRI data acquisition, participants had to judge which one of two visual stimuli was brighter. In predictable blocks, the stimuli appeared temporally aligned with their button press (active) or aligned with an automatically generated cue (passive). In unpredictable blocks, stimuli were presented with a variable delay after button press/cue, respectively. Eye tracking was performed to investigate pupil-size changes and to ensure proper fixation. Self-generated stimuli were perceived as darker and led to less neural activation in visual areas than their passive counterparts, indicating sensory attenuation for self-generated stimuli. These effects were accompanied by a larger pupil size during self-generated stimuli, which correlated negatively with BOLD response: the larger the pupil, the smaller the BOLD amplitude in visual areas. An effect of temporal predictability was not found. Therefore, our results suggest that sensory attenuation in visual cortex is mainly driven by action-based predictive mechanisms, not by temporal predictability. This effect may be mediated by changes in pupil diameter. Altogether, these results emphasize the role of the efference copy in the processing of sensory action consequences.
Acknowledgement: SFB/Transregio 135 (DFG), IRTG 1901 (DFG), STR 1146/8-1 (DFG) and STR 1146/9-1 (DFG)