Sensorimotor learning in children and adults: Exposure to frequency-altered auditory feedback during speech production.

Auditory feedback plays an important role in the acquisition of fluent speech; however, this role may change once speech is acquired and individuals no longer experience persistent developmental changes to the brain and vocal tract. For this reason, we investigated whether the role of auditory feedback in sensorimotor learning differs across children and adult speakers. Participants produced vocalizations while they heard their vocal pitch predictably or unpredictably shifted downward one semitone. The participants' vocal pitches were measured at the beginning of each vocalization, before auditory feedback was available, to assess the extent to which the deviant auditory feedback modified subsequent speech motor commands. Sensorimotor learning was observed in both children and adults, with participants' initial vocal pitch increasing following trials where they were exposed to predictable, but not unpredictable, frequency-altered feedback. Participants' vocal pitch was also measured across each vocalization, to index the extent to which the deviant auditory feedback was used to modify ongoing vocalizations. While both children and adults were found to increase their vocal pitch following predictable and unpredictable changes to their auditory feedback, adults produced larger compensatory responses. The results of the current study demonstrate that both children and adults rapidly integrate information derived from their auditory feedback to modify subsequent speech motor commands. However, these results also demonstrate that children and adults differ in their ability to use auditory feedback to generate compensatory vocal responses during ongoing vocalization. Since vocal variability also differed across the children and adult groups, these results also suggest that compensatory vocal responses to frequency-altered feedback manipulations initiated at vocalization onset may be modulated by vocal variability.

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.