Neural responses to the sensory effects of willed motor actions

Our sense of agency and dynamic motor control relies on sensory attenuation, a phenomenon that distinguishes the sensory effects of our actions from sensations caused by the external world. This distinction is realized by the brain using motor commands to anticipate and modulate sensory input resulting from self-initiated actions. A putative electrophysiological index of sensory attenuation is the reduction of the auditory N1 component in the electroencephalogram (EEG). However, the underlying causes of electrophysiological sensory attenuation are debated. Previous research is almost entirely limited to auditory stimuli, and two action–sensation pairings in particular; specifically, vocalizing to produce speech sounds, and button pressing for tones. The aims of this thesis were to elucidate how sensory attenuation may be modulated by the strength of the existing causal relationship between an action (e.g., speaking) and its sensory effect (e.g., hearing one's own voice), and to determine if the phenomenon can occur in non-auditory modalities. To achieve these aims, this thesis reports a series of experiments that measured the event-related potential (ERP) response evoked by a range of action–sensation pairings new to the literature. The first study found that button press-initiated tones evoked reduced auditory ERPs uncorrelated to the amplified visual ERPs evoked by button press-initiated pattern reversals. The next two studies debuted a saccade initiation paradigm, and found that ERP attenuation depended on the likelihood of the initiating action (i.e., saccades or button presses) being paired in everyday life with stimulation within the modality of the sensory effect (i.e., flashes or tones). The fourth study debuted a blow initiation paradigm to address stimulus confounds in the vocal production paradigm that is typically used in studies of supposed motor prediction dysfunction in schizophrenia, and found that blow-initiated tones evoked greater auditory ERP attenuation than that evoked by button presses and saccades. Collectively, the studies reported in this thesis support the notion that auditory ERP attenuation relates to the habitual causal relationship between motor output region and the modality of subsequent sensory input. Furthermore, the equivocal outcomes of the visual studies complicate accounts of electrophysiological sensory attenuation based on motor prediction alone