Flexibility and Neural Correlates of Action-Sound Predictions

To interact efficiently with our environment, our brain predicts the sensory effects of our actions and compares them with the actual outcomes. This allows us to adapt our actions when predictions and sensory outcomes mismatch. While this process is generally well understood for action-sound predictions, it is an open question how flexibly these predictions can adapt in frequently changing environments, as they occur in real life. To investigate the flexibility of top-down predictions, we asked participants (N = 41) to press one of two buttons, a left-hand and a right-hand button, and switch hands autonomously. One button frequently produced a sound (80%) and rarely no sound. The other button frequently generated no sound (80%) and rarely produced a sound. In a third, separate condition, each button produced a sound in 50% of the trials. Unexpected sounds and unexpected sound omissions elicited a series of error-related brain responses in the electroencephalogram (EEG) at different levels of auditory processing, including a mismatch negativity (MMN) and the P3 complex for unexpected sounds, and the oN1, oN2, and oP3 complex for unexpected omissions. Moreover, unexpected sounds elicited an equivalent MMN--regardless of whether silence was expected (80%) or no reliable expectation was possible (50%), while later P3 components showed different amplitudes. Our results demonstrate flexible action-sound predictions at sensory and higher cortical levels. Furthermore, they indicate that predicted silence does not have an explicit sensory representation at lower levels but emerges at later stages, when higher-level information has been integrated.