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No causal role for premotor cortex in the perception or misperception of degraded speech: Evidence from TMS
Poster Session D, Saturday, October 26, 10:30 am - 12:00 pm, Great Hall 3 and 4
Valeriya Tolkacheva1, Sonia Brownsett2,3, Katie McMahon4,5, Greig de Zubicaray1; 1Queensland University of Technology, School of Psychology and Counselling, Queensland, Australia, 2Queensland Aphasia Research Centre, School of Health and Rehabilitation Sciences, University of Queensland, Queensland, Australia, 3Centre of Research Excellence in Aphasia Recovery and Rehabilitation, La Trobe University, Melbourne, Victoria, Australia, 4Herston Imaging Research Facility, Royal Brisbane & Women’s Hospital, Queensland, Australia, 5Queensland University of Technology, School of Clinical Sciences and Centre for Biomedical Technologies, Queensland, Australia
A number of studies have shown that listeners can use prior knowledge to predict the content of noisy speech signals, enhancing perception. However, this process can also elicit misperceptions. The neural mechanisms responsible for both effects remain underspecified, although there is relatively consistent evidence for involvement of the bilateral posterior superior temporal gyri (pSTG) in speech perception in noise using a range of syllable, word and sentence stimuli (Kennedy-Higgins et al., 2020; Tolkacheva et al., 2024). The roles of the motor and premotor cortices in speech perception are debated. While there is evidence for primary (M1) and premotor cortex (PMC) involvement in sublexical, syllable perception in noise (Brisson & Tremblay, 2021; Nuttal et al., 2016), there is little evidence using natural speech. In this study we explored the role of the PMC in perception and misperception of degraded speech. We used repetitive transcranial magnetic stimulation (rTMS) and a prime-probe paradigm to investigate causal roles for the PMC and left pSTG in speech perception and misperception using identical materials to Tolkacheva et al. (2024). Eighteen listeners were presented with spectrotemporally degraded probe sentences preceded by a clear prime. To produce misperceptions, we created partially mismatched pseudo-sentence probes via homophonic nonword transformations (e.g., The little girl was excited to lose her first tooth - Tha fittle girmn wam expited du roos har derst cooth). We expected to replicate our previous finding that inhibitory rTMS to the left pSTG impairs priming of real, but not pseudo-sentences compared to the stimulation of a control region (Vertex). We also hypothesised that TMS applied to the PMC would impair priming of both real and pseudo-sentences if this region plays a role in processing of lexical and/or sublexical information during speech perception. Compared to a control site (Vertex), inhibitory stimulation of the left pSTG selectively disrupted priming of real but not pseudo-sentences. However, inhibitory stimulation of the PMC did not significantly influence perception of real sentences or misperceptions of pseudo-sentences. These results confirm a role for the left pSTG in the perception of degraded speech. However, they do not support a role for the PMC in either lexical or sublexical processing during perception of degraded speech using sentence stimuli. These findings have significant implications for neurobiological models of speech perception. [1] Kennedy-Higgins, D., Devlin, J., Nuttall, H., & Adank, P. (2020). The Causal Role of Left and Right Superior Temporal Gyri in Speech Perception in Noise: A Transcranial Magnetic Stimulation Study. Journal of Cognitive Neuroscience, 32(6), 1092-1103. [2] Tolkacheva, V., Brownsett, S., McMahon, K., & de Zubicaray, G. (2024). Perceiving and misperceiving speech: lexical and sublexical processing in the superior temporal lobes. Cerebral cortex (New York, N.Y. : 1991), 34(3), bhae087. [3] Brisson, V., & Tremblay, P. (2021). Improving speech perception in noise in young and older adults using transcranial magnetic stimulation. Brain and Language, 222, 105009. [4] Nuttall, H., Kennedy-Higgins, D., Hogan, J., Devlin, J., & Adank, P. (2016). The effect of speech distortion on the excitability of articulatory motor cortex. NeuroImage, 128, 218-226.
Topic Areas: Speech Perception, Phonology