Functional role of delta and theta band oscillations for auditory feedback processing during vocal pitch motor control.

Roozbeh Behroozmand,Nadine Ibrahim,Charles R Larson,Oleg Korzyukov,Donald A Robin

doi:10.3389/fnins.2015.00109

Abstract

The answer to the question of how the brain incorporates sensory feedback and links it with motor function to achieve goal-directed movement during vocalization remains unclear. We investigated the mechanisms of voice pitch motor control by examining the spectro-temporal dynamics of EEG signals when non-musicians (NM), relative pitch (RP), and absolute pitch (AP) musicians maintained vocalizations of a vowel sound and received randomized ± 100 cents pitch-shift stimuli in their auditory feedback. We identified a phase-synchronized (evoked) fronto-central activation within the theta band (5–8 Hz) that temporally overlapped with compensatory vocal responses to pitch-shifted auditory feedback and was significantly stronger in RP and AP musicians compared with non-musicians. A second component involved a non-phase-synchronized (induced) frontal activation within the delta band (1–4 Hz) that emerged at approximately 1 s after the stimulus onset. The delta activation was significantly stronger in the NM compared with RP and AP groups and correlated with the pitch rebound error (PRE), indicating the degree to which subjects failed to re-adjust their voice pitch to baseline after the stimulus offset. We propose that the evoked theta is a neurophysiological marker of enhanced pitch processing in musicians and reflects mechanisms by which humans incorporate auditory feedback to control their voice pitch. We also suggest that the delta activation reflects adaptive neural processes by which vocal production errors are monitored and used to update the state of sensory-motor networks for driving subsequent vocal behaviors. This notion is corroborated by our findings showing that larger PREs were associated with greater delta band activity in the NM compared with RP and AP groups. These findings provide new insights into the neural mechanisms of auditory feedback processing for vocal pitch motor control.

Highlights

The ability to control voice fundamental frequency (F0) is essential for animal vocalization and human speech
In that previous study (Behroozmand et al, 2014), results showed that the N1 component of event-related potential (ERP) in response to pitch-shift stimuli was significantly stronger in the right hemisphere for both absolute pitch (AP) and relative pitch (RP) musicians compared with the NM group
We found that the P2 component of ERPs in the left hemisphere was significantly stronger in AP and RP musicians compared with NMs, and was stronger for AP compared with RP musicians

Summary

Introduction

The ability to control voice fundamental frequency (F0) is essential for animal vocalization and human speech. The notion of feedforward and feedback integration mechanisms has been supported by evidence from studies that investigated behavioral vocal responses to pitch perturbation in voice auditory feedback Findings of these studies have shown that humans control the pitch of their vocalizations by generating compensatory vocal responses that change their voice pitch in the opposite direction to pitch-shift stimuli in the auditory feedback (Larson, 1998; Chen et al, 2007; Liu and Larson, 2007; Behroozmand et al, 2012). These compensatory vocal mechanisms have been suggested to enable an individual to use online auditory feedback for vocal production and motor control

Methods

Results

Conclusion