INVESTIGATING ALPHA OSCILLATORY POWER AS A NEURAL MARKER OF AUDITORY SELECTIVE INHIBITION UNDER CONDITIONS OF REVERBERATION

Abstract

Alpha oscillatory power in the parietal and auditory cortices is an observable signature of auditory selective inhibition. In naturalistic settings, the reverberation of speech signals reduces the reliability of spatial and pitch cues used to encode speech. Listeners employ early pitch discrimination to determine a speaker’s gender, and selectively attend to distinct cues in male and female voices. Higher acoustic detail of speech distractors has been shown to enhance distraction in listening tasks, manifested as a higher alpha response. Analysis was performed on data from a task where a male voice and a female voice were simultaneously presented in differing levels of reverberation, with subjects instructed to attend to one, while the other was a distractor. It was hypothesised that with increased reverberation, alpha power (as a sign of distraction) will increase. Since male pitch is degraded less by reverberation and therefore less distracting, it was also predicted that when the task-relevant speech stream is a female voice with a male voice distractor, there would be a higher alpha power than if the task relevant speech was male and the distractor female. Contrary to our hypothesis, it was found that the sex of the speaker and distractor did not cause significant change in alpha power. An alternative account for selective attention based on voice characteristics is presented, whereby selective attention exploits perceptual cues instead of spatial cues for speech signal segregation.