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Ambient noise induces changes across the perisylvian network during speech perception and production
Poster Session E, Friday, October 2, 11:00 am - 1:00 pm, Wangari Maathai
This poster is part of the Sandbox Series.
Latane Bullock1, Alan Bush2, Matteo Vissani2, Frank H Guenther3,4, R Mark Richardson2; 1Program in Speech and Hearing Bioscience and Technology, Division of Medical Sciences, Harvard Medical School, Boston, MA, 02115, USA, 2Department of Neurosurgery, Massachusetts General Hospital, Boston, MA, 02114, USA, 3Department of Speech, Language, and Hearing Sciences, Boston University, Boston, MA, United States, 4Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
INTRODUCTION. The neural basis of the Lombard Effect—an increase in voice intensity in response to background noise—is unclear, despite the long history and importance of the effect to neurologists and speech scientists. Animal model research has largely implicated subcortical structures in mediating the increase in intensity, but the effect is more complex in humans, and likely relies on both subcortical and cortical mechanisms. We recorded neural activity in movement disorder patients undergoing deep brain stimulation implant surgeries while they repeated sentences in ambient multitalker background noise (NOISE) or in quiet (QUIET). In basal ganglia, firing rate and local field potential broadband gamma activity (LFP-BGA, 70-150 Hz) track the levels of background noise but, contrary to our prediction, did not encode vigor of speech production (Bullock…Richardson 2026 bioRxiv). Here, we report on cortical perisylvian speech regions. We hypothesized that a) ambient noise interferes with speech stimulus encoding in the auditory cortex and b) ventral sensorimotor cortex would encode the absolute voice intensity changes induced by NOISE. METHODS. 23 patient-participants completed the speech-in-noise sentence repetition task while we recorded from two ECoG strips temporarily placed over perisylvian speech regions. Using the LFP-BGA signal, we investigated temporal auditory (superior temporal gyrus) and sensorimotor (pre-and post-central gyri) areas during speech perception and production. We fit group-level, per-region linear mixed-effects models (LMEs) to characterize each region’s activity across different task epochs (baseline, stimulus, speech) and conditions (NOISE, QUIET). RESULTS. We found two different sensorimotor regions activated during speech perception: one in anterior mid-precentral gyrus, and the other a more dorsal region over the central sulcus. In the presence of ambient noise, both auditory (p<1e-6) and motor regions (mid-precentral gyrus, p=1.9e-4) activated less strongly to the stimulus. As hypothesized, ambient noise degraded the encoding of the stimulus in the auditory cortex (within-channel trial-to-trial variability in NOISE relative to QUIET, permutation test p=0.0084). During speech production, participants spoke louder in the NOISE condition (paired t-test, p<1e-6). Contrary to our predictions, we did not observe a correlation between LFP-BGA in pre- and post-central gyrus and speech volume at the cohort ROI level. Exploratory analyses revealed, nonetheless, that within-utterance vowel intensity modulation was significantly decodable in 18/19 subjects (permutation test; FDR correction across subjects, q < 0.05). CONCLUSIONS. During perception, ambient noise a) increases baseline activity in auditory cortex, b) decreases stimulus-window response magnitudes, and c) degrades the quality of speech stimulus encoding. During production, ambient noise a) induces higher baseline speech intensity but b) that change isn’t strongly encoded in motor regions, despite c) motor cortex encoding prosodic fluctuations in vowel intensity over the course of a sentence. Our findings suggest motor regions encode relative prosodic modulation within an utterance but not the absolute loudness level set by environmental context. Our results may have implications for models of speech production, the treatment of voice loudness impairment in movement disorder patients, and our understanding of feedback-modulated speech disorders such as stuttering.
Topic Areas: Speech Motor Control, Speech Perception