Abstract
When people hear unexpected perturbations in auditory feedback, they produce rapid compensatory adjustments of their vocal behavior. Recent evidence has shown enhanced vocal compensations and cortical event-related potentials (ERPs) in response to attended pitch feedback perturbations, suggesting that this reflex-like behavior is influenced by selective attention. Less is known, however, about auditory-motor integration for voice control during divided attention. The present cross-modal study investigated the behavioral and ERP correlates of auditory feedback control of vocal pitch production during divided attention. During the production of sustained vowels, 32 young adults were instructed to simultaneously attend to both pitch feedback perturbations they heard and flashing red lights they saw. The presentation rate of the visual stimuli was varied to produce a low, intermediate, and high attentional load. The behavioral results showed that the low-load condition elicited significantly smaller vocal compensations for pitch perturbations than the intermediate-load and high-load conditions. As well, the cortical processing of vocal pitch feedback was also modulated as a function of divided attention. When compared to the low-load and intermediate-load conditions, the high-load condition elicited significantly larger N1 responses and smaller P2 responses to pitch perturbations. These findings provide the first neurobehavioral evidence that divided attention can modulate auditory feedback control of vocal pitch production.
Highlights
Auditory feedback is critical for the production of proper speech sounds (Hickok et al, 2011)
In the context of speech motor control, Tumber et al (2014) reported that participants who were exposed to pitch perturbations during vocalization produced smaller vocal compensations when they actively attended to a rapid serial visual presentation (RSVP) of letters relative to when they passively viewed the RSVP, suggesting that the attentional load of the RSVP task reduced the available attentional resources for the detection and/or correction for production errors
Differential effects of divided attention were observed on the cortical N1 and P2 responses to attended pitch perturbations
Summary
Auditory feedback is critical for the production of proper speech sounds (Hickok et al, 2011). Previous research has repeatedly shown that attended auditory stimuli elicit larger event-related potentials (ERPs) (Hink and Hillyard, 1976; Stevens et al, 2006) and enhanced brain activity in the auditory cortex (Ahveninen et al, 2006; Johnson and Zatorre, 2006; Sabri et al, 2008) relative to unattended auditory stimuli These findings suggest that the perception of speech sounds is highly dependent on attention. The results showed that attending to pitch perturbations elicited significantly larger vocal compensations and P2 responses relative to ignoring pitch perturbations (i.e., attending to flashing lights) and passively observing the bimodal stimuli These neurobehavioral findings can be accounted for by the gain-based theory of selective attention (Hillyard et al, 1998), according to which selective attention increases the gain for neurons involved in auditory-vocal integration which in turn facilitates the detection/correction of voice feedback errors
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