RT Journal Article
SR Electronic
T1 Electrocorticographic responses to time-compressed speech vary across the cortical auditory hierarchy
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 354464
DO 10.1101/354464
A1 Ido Davidesco
A1 Thomas Thesen
A1 Christopher J Honey
A1 Lucia Melloni
A1 Werner Doyle
A1 Orrin Devinsky
A1 Oded Ghitza
A1 Charles Schroeder
A1 David Poeppel
A1 Uri Hasson
YR 2018
UL http://biorxiv.org/content/early/2018/06/22/354464.abstract
AB Human listeners understand spoken language across a variety of rates, but when speech is presented three times or more faster than its usual rate, it becomes unintelligible. How the brain achieves such tolerance and why speech becomes unintelligible above certain rates is still unclear. We addressed these questions using electrocorticography (ECoG) recordings in 7 epileptic patients (two female). Patients rated the intelligibility of sentences presented at the original rate (100%), speeded rates (33% or 66% of the original sentence duration) and a slowed rate (150%). We then examined which parameters of the neural response covary with the transition from intelligible to unintelligible speech. Specifically, we asked whether neural responses: 1) track the acoustic envelope of the incoming speech; 2) “scale” with speech rate, i.e. whether neural responses elicited by slowed and speeded sentences can be linearly scaled to match the responses to the original sentence. Behaviorally, intelligibility was at ceiling for speech rates of 66% and above, but dropped significantly for the 33% rate. At the neural level, Superior Temporal Gyrus regions (STG) in close proximity to A1 (‘low-level’) tracked the acoustic envelope and linearly scaled with the input across all speech rates, irrespective of intelligibility. In contrast, secondary auditory areas in the STG as well as the inferior frontal gyrus and angular gyrus (‘high-level’) tracked the acoustic envelope and linearly scaled with input only for intelligible speech. These results help reconcile seemingly contradictory previous findings and provide better understanding of how information processing unfolds along the cortical auditory hierarchy.