ERP correlates of the magnitude of pitch errors detected in the human voice.

Auditory event-related potentials (ERP)s of the P1-N1-P2 complex are modulated when participants hear frequency-altered feedback (FAF) regarding their ongoing vocal productions. However, the relationship between feedback perturbation magnitudes and the resultant neural responses is at present unclear. In the present study, we exposed speakers to FAF of different magnitudes ranging from 0 to 400 cents. Vocal responses and P1-N1-P2-N2 ERPs were examined in an attempt to relate variation in the magnitude of the imposed feedback perturbation with variation in vocal and neural responses. Overall, vocal response magnitudes remained relatively consistent in response to smaller feedback perturbations (<250 cents), while larger feedback perturbations (>300 cents) resulted in decreased vocal response magnitudes. P1 amplitudes were found to increase in a non-specific manner in response to FAF. Conversely, N1 amplitudes displayed increased specificity: small feedback perturbations evoked one size of response, while larger feedback perturbations resulted in larger responses. The P2 component showed the most systematic amplitude modulation as feedback perturbation magnitude increased. A regression analysis highlighted the relationship between vocal response magnitude and P2 amplitude, with both vocal response magnitude and P2 amplitude increasing in response to perturbations between 50 and 250 cents, and then decreasing in response to larger perturbations. Although not generally observed in FAF studies, a robust N2 was also found; N2 amplitudes increased as stimulus magnitudes increased. The pattern of P1-N1-P2-N2 amplitude modulation in response to different magnitudes of FAF indicates that these components reflect processes involved in the detection and correction of unintended changes in auditory feedback during speech.