Differential Effects of Self-Initiated, Externally Triggered, and Passive Movements on Action-Outcome Processing: Insights From Sensory and Motor-Preparatory Event Related Potentials.

Self-initiated voluntary actions are different from externally triggered or passive movements. However, it remains unclear how these movements affect action feedback processing and how they are prepared. Here, we focus on the sensory and motor-preparatory event-related potentials. Participants made active (self-initiated, 700 ms lower limit), quick (respond to a cue as quickly as possible), and passive (finger moved by device) button presses that triggered visual stimuli. The active and quick conditions elicited lower visual N1-P2 peak-to-peak amplitudes than the passive condition but did not significantly differ from each other. For prestimulus ERPs (lateralized/readiness potential; L/RP), all conditions showed a negative shift in RP, with lower amplitudes in the quick than in the active condition. There were no significant differences between active and passive. For the LRP, the active and quick conditions showed a sharp deflection shortly before the button press. The amplitude of both conditions was significantly lower than passive around 100 ms before the movement. Our results suggest that active and quick movements involve similar feedback prediction, even though they are prepared differently. They thus offer a finer-grained specification of the efference copy mechanism.