Motor signals modulate cortical but not subcortical processing of self-initiated sounds

When we produce sounds ourselves, the brain modulates the auditory neural response through an efference copy mechanism, allowing us to distinguish between self-initiated and externally generated auditory inputs. However, the precise level of the auditory pathway at which this attenuation occurs remains unclear. While evidence from animal models suggests that early auditory processing of self-generated sounds may be modulated by corticofugal signaling, localized cortical modulation would preserve the high-fidelity subcortical sound encoding while allowing flexible, context-dependent processing at higher levels. To probe potential motor influences in the early auditory system, we collected scalp-recorded frequency following responses (FFRs) from 33 normal-hearing adults during active (self-initiated) and passive (externally presented) listening conditions using a 170 ms speech stimulus. Data were collected with a vertical montage that emphasizes subcortical generators of the FFR. We observed no significant differences in the FFR between active and passive conditions in spectral power, response amplitude, pitch tracking, onset latency, or phase consistency. In contrast, cortical event-related potentials showed motor-induced suppression (MIS): reduced early peak amplitudes in the active condition after correcting for motor signals, increased phase consistency prior to auditory feedback, and more precise phase consistency at sound offset. In addition to indicating FFRs can be collected during a wider range of behavioral tasks without substantial motor contamination, our observation of the canonical MIS in cortical signals but not in FFRs suggests that MIS of self-initiated sounds primarily affects later stages of auditory processing rather than the early encoding reflected in the FFR.