What exactly is missing here? The sensory processing of unpredictable omissions is modulated by the specificity of expected action‐effects
Participants pressed two keys to generate tones, which were rarely omitted. Key‐presses either generated always a single tone, one of two tones with hand‐specific associations or randomly one of two tones. An early oN1 was reliably observed following omissions in the single tone condition only. A late oN1 was reliably elicited in the single tone and hand‐specific conditions. While the oN1 indicates processing costs/benefits, later on, similar oP3 responses were observed in all conditions.
We select our actions according to the desired outcomes; for instance, piano players press certain keys to generate specific musical notes. It is well‐described that the omission of a predicted action‐effect may elicit prediction error signals in the brain, but what happens in the case of simultaneous effector‐specific (by contrast to effector‐unspecific) predictions? To answer this question, we asked participants to press left and right keys to generate tones A and B; based on the action‐effect association, the tones’ identity was either predictable or unpredictable, while rarely, the expected input was omitted. Crucially, the data show that omissions following hand‐specific associations reliably elicited a late omission N1 (oN1) component, by contrast to the hand‐unspecific associations, where the late oN1 was rather weak. An additional condition where both key‐presses generated a unique tone was implemented. Here, rare omissions of the expected tone generated both early and late oN1 responses, by contrast to the condition in which two simultaneous action‐effect representations had to be maintained, where only late oN1 responses were elicited. Finally, omission P3 (oP3) responses were strongly elicited for all omission types without differences, indicating that a general expectation based on a tone presentation (rather than which tone), is likely indexed at this stage. The present results emphasize the top‐down effects of action intention on the sensory processing of omissions, where unspecific (vs. specific) and multiple (vs. single) action‐effect representations are associated with processing costs at the early sensory levels.