The role of hearing ability and speech distortion in the facilitation of articulatory motor cortex

Nuttall, Helen and Kennedy-Higgins, Daniel and Devlin, Joseph T. and Adank, Patti (2017) The role of hearing ability and speech distortion in the facilitation of articulatory motor cortex. Neuropsychologia, 94. pp. 13-22. ISSN 0028-3932

[thumbnail of Neuropsychologia_Manuscript_HENuttall_Revision3]
PDF (Neuropsychologia_Manuscript_HENuttall_Revision3)
Neuropsychologia_Manuscript_HENuttall_Revision3.pdf - Accepted Version
Available under License Creative Commons Attribution-NonCommercial-NoDerivs.

Download (633kB)


Excitability of articulatory motor cortex is facilitated when listening to speech in challenging conditions. Beyond this, however, we have little knowledge of what listener-specific and speech-specific factors engage articulatory facilitation during speech perception. For example, it is unknown whether speech motor activity is independent or dependent on the form of distortion in the speech signal. It is also unknown if speech motor facilitation is moderated by hearing ability. We investigated these questions in two experiments. We applied transcranial magnetic stimulation (TMS) to the lip area of primary motor cortex (M1) in young, normally hearing participants to test if lip M1 is sensitive to the quality (Experiment 1) or quantity (Experiment 2) of distortion in the speech signal, and if lip M1 facilitation relates to the hearing ability of the listener. Experiment 1 found that lip motor evoked potentials (MEPs) were larger during perception of motor-distorted speech that had been produced using a tongue depressor, and during perception of speech presented in background noise, relative to natural speech in quiet. Experiment 2 did not find evidence of motor system facilitation when speech was presented in noise at signal-to-noise ratios where speech intelligibility was at 50% or 75%, which were significantly less severe noise levels than used in Experiment 1. However, there was a significant interaction between noise condition and hearing ability, which indicated that when speech stimuli were correctly classified at 50%, speech motor facilitation was observed in individuals with better hearing, whereas individuals with relatively worse but still normal hearing showed more activation during perception of clear speech. These findings indicate that the motor system may be sensitive to the quantity, but not quality, of degradation in the speech signal. Data support the notion that motor cortex complements auditory cortex during speech perception, and point to a role for the motor cortex in compensating for differences in hearing ability.

Item Type:
Journal Article
Journal or Publication Title:
Additional Information:
This is the author’s version of a work that was accepted for publication in Neuropsychologia. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Neuropsychologia, 94, 2017 DOI: 10.1016/j.neuropsychologia.2016.11.016
Uncontrolled Keywords:
?? speech perceptionmotor cortextranscranial magnetic stimulationmotor evoked potentialscognitive neurosciencebehavioral neuroscienceexperimental and cognitive psychology ??
ID Code:
Deposited By:
Deposited On:
25 Jan 2017 16:16
Last Modified:
31 Dec 2023 00:45