P 144. Activity prior to motor cortex and the sensation of agency modulate brain responses to self-initiated sounds

Introduction

One of the functions of the brain is to predict sensory consequences of our own actions. In auditory processing self-initiated sounds evoke a smaller auditory brain response than passive sound exposure of the same sound sequence [1]. Previous work suggests that this response attenuation reflects a predictive mechanism to differentiate the sensory consequences of one’s own actions from other sensory input [2]. On a psychological level correctly predicted sensory feedback has been linked to a pre-reflective sensation of self-agency (feeling of coherence in action processing) [3] which is formed in premotor areas involved in movement planning [4].

Objectives

We addresses the question whether attenuation of brain responses to self-initiated sounds can be explained by brain activity leading up to, but not including, the motor cortex. Moreover, the relation between attenuated auditory brain responses to self-initiated sounds and the pre-reflective sensation of agency was investigated.

Materials and methods

Event-related brain potentials (ERPs) from the human scalp of 17 participants were recorded in response to sounds initiated by a button press. In one experimental condition, participants moved a finger to press the button voluntarily, whereas, in another condition, we initiated a similar finger movement involuntarily by stimulating the corresponding region of the primary motor cortex with transcranial magnetic stimulation (TMS). No sensation of agency was experienced for involuntary movements as no motor plans were available.

Results

A portion of the brain response evoked by the sounds, the N1–P2 complex, was reduced in amplitude only following a voluntary, self-initiated, movement, but not following a movement initiated by motor cortex stimulation.

Conclusion

Our findings demonstrate that sensory attenuation of brain responses to self-initiated sounds depends on a pre-reflective sensation of agency and on predictive mechanisms that operate prior to the activation of the primary motor cortex. The present results support the assumptions of an internal forward-model account [2].

Funding sources

This work was supported by the Erasmus Mundus Student Exchange Network in Auditory Cognitive Neuroscience and a Reinhart-Koselleck Grant of the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG, Project 375/20-1).