title: The role of phase-locking to the temporal envelope of speech in auditory perception and speech intelligibility.
abstract: The temporal envelope of speech is important for speech intelligibility. Entrainment of cortical oscillations to the speech temporal envelope is a putative mechanism underlying speech intelligibility. Here we used magnetoencephalography (MEG) to test the hypothesis that phase-locking to the speech temporal envelope is enhanced for intelligible compared with unintelligible speech sentences. Perceptual "pop-out" was used to change the percept of physically identical tone-vocoded speech sentences from unintelligible to intelligible. The use of pop-out dissociates changes in phase-locking to the speech temporal envelope arising from acoustical differences between un/intelligible speech from changes in speech intelligibility itself. Novel and bespoke whole-head beamforming analyses, based on significant cross-correlation between the temporal envelopes of the speech stimuli and phase-locked neural activity, were used to localize neural sources that track the speech temporal envelope of both intelligible and unintelligible speech. Location-of-interest analyses were carried out in a priori defined locations to measure the representation of the speech temporal envelope for both un/intelligible speech in both the time domain (cross-correlation) and frequency domain (coherence). Whole-brain beamforming analyses identified neural sources phase-locked to the temporal envelopes of both unintelligible and intelligible speech sentences. Crucially there was no difference in phase-locking to the temporal envelope of speech in the pop-out condition in either the whole-brain or location-of-interest analyses, demonstrating that phase-locking to the speech temporal envelope is not enhanced by linguistic information.
authors.affiliation: York Neuroimaging Center, Heslington, UK.
authors.forename: Rebecca E
authors.initials: RE
authors.lastname: Millman
authors.forename: Sam R
authors.initials: SR
authors.lastname: Johnson
authors.forename: Garreth
authors.initials: G
authors.lastname: Prendergast
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D013065:Speech Intelligibility / Q000502:physiology*; D013067:Speech Perception / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult