Neuronal Mechanisms of Voice Control Are Affected by Implicit Expectancy of Externally Triggered Perturbations in Auditory Feedback

Abstract

Accurate vocal production relies on several factors including sensory feedback and the ability to predict future challenges to the control processes. Repetitive patterns of perturbations in sensory feedback by themselves elicit implicit expectations in the vocal control system regarding the timing, quality and direction of perturbations. In the present study, the predictability of voice pitch-shifted auditory feedback was experimentally manipulated. A block of trials where all pitch-shift stimuli were upward, and therefore predictable was contrasted against an unpredictable block of trials in which the stimulus direction was randomized between upward and downward pitch-shifts. It was found that predictable perturbations in voice auditory feedback led to a reduction in the proportion of compensatory vocal responses, which might be indicative of a reduction in vocal control. The predictable perturbations also led to a reduction in the magnitude of the N1 component of cortical Event Related Potentials (ERP) that was associated with the reflexive compensations to the perturbations. We hypothesize that formation of expectancy in our study is accompanied by involuntary allocation of attentional resources occurring as a result of habituation or learning, that in turn trigger limited and controlled exploration-related motor variability in the vocal control system.

A temporal predictive code for voice motor control: Evidence from ERP and behavioral responses to pitch-shifted auditory feedback

“…In addition, these findings suggest that exposure to repeated presentations of predictable stimuli results in the increased contribution of feedforward mechanisms during vocal motor control. This reasoning supports the framework for predictions by the internal forward model: learned predictions result in more accurate efference copies and, consequently, a decreased mismatch in sensory feedback (Chen et al, 2012; Korzyukov et al, 2012; Scheerer and Jones, 2014; Wang et al, 2014; Wolpert and Flanagan, 2001). …”

“…In the study by Scheerer & Jones (Scheerer and Jones, 2014), behavioral vocal responses to predictable and unpredictable pitch-shift stimulus magnitude were examined and they reported that the magnitude of vocal responses was significantly reduced for predictable vs. unpredictable stimuli. Behroozmand et al (Behroozmand et al, 2012) and Korzyukov et al (Korzyukov et al, 2012) examined the effect of pitch-shift stimulus direction predictability and found that the magnitude of opposing (compensatory) vocal responses to unpredictable stimulus direction was significantly larger than following responses (Behroozmand et al, 2012), and there was a significantly larger number of opposing responses for unpredictable vs. predictable stimulus direction (Korzyukov et al, 2012). Korzyukov et al (Korzyukov et al, 2012) and Scheerer & Jones (Scheerer and Jones, 2014) also reported that the amplitude of the N1 component of ERPs was significantly reduced for predictable vs. unpredictable stimulus direction and magnitude, respectively.…”

“…Behroozmand et al (Behroozmand et al, 2012) and Korzyukov et al (Korzyukov et al, 2012) examined the effect of pitch-shift stimulus direction predictability and found that the magnitude of opposing (compensatory) vocal responses to unpredictable stimulus direction was significantly larger than following responses (Behroozmand et al, 2012), and there was a significantly larger number of opposing responses for unpredictable vs. predictable stimulus direction (Korzyukov et al, 2012). Korzyukov et al (Korzyukov et al, 2012) and Scheerer & Jones (Scheerer and Jones, 2014) also reported that the amplitude of the N1 component of ERPs was significantly reduced for predictable vs. unpredictable stimulus direction and magnitude, respectively. Moreover, Scheerer & Jones (Scheerer and Jones, 2014) found that the latency of the P1 and N1 components was significantly shorter for predictable stimulus magnitude.…”

“…Although behavioral vocal responses were not measured in Chen et al’s study (Chen et al, 2012), they reported that the amplitude of the P2 ERP responses was reduced for manually-triggered temporally-predictable vs. unpredictable pitch-shift stimuli. Findings of these studies have suggested that the expectancy of the predictable stimulus eventually develops into recognition of the perturbation as being an external stimulus thereby leading to reduced vocal compensation (i.e., opposing responses) and a change in the underlying sensory-motor neural processes as indexed by modulation of the P1/N1/P2 components (Behroozmand et al, 2012; Chen et al, 2012; Korzyukov et al, 2012; Scheerer and Jones, 2014). In addition, these findings suggest that exposure to repeated presentations of predictable stimuli results in the increased contribution of feedforward mechanisms during vocal motor control.…”

“…Although the behavioral and neural correlates of vocalization have been examined for predictable pitch-shift stimulus magnitude and direction (Behroozmand et al, 2012; Korzyukov et al, 2012; Scheerer and Jones, 2014), research on temporal predictability effects on voice motor control is limited. Previous studies have shown that the suppression of neural responses in the auditory cortex in response to pure tones (Aliu et al, 2009) and speech (Behroozmand et al, 2011; Chen et al, 2012) develops for zero time delays but does not generalize to non-zero delays between feedforward predictions and sensory feedback perturbation.…”