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Preliminary evidence for tuning of the auditory system during speech planning
Poster Session C, Saturday, September 13, 11:00 am - 12:30 pm, Field House
Yaser Merrikhi1, Anuradha Jyothi Sreedhar1, Ayoub Daliri1; 1College of Health Solutions, Arizona State University, Tempe, AZ, United States
The central nervous system (CNS) closely monitors auditory feedback during speech production—a process critical for both speech acquisition and maintenance (Perkell, 2012; Guenther & Vladusich, 2012). Impairments in auditory monitoring are linked to various speech disorders, including stuttering (Terband et al., 2009; Daliri et al., 2017). While current models of speech production emphasize monitoring after speech initiation (Houde & Nagarajan, 2011; Hickok, 2012; Guenther, 2016), they do not account for whether or how the CNS optimizes the auditory system in advance of speech onset. Understanding such sensory preparatory mechanisms has theoretical and clinical implications but remains largely unexplored. This study aims to elucidate the predictive modulation of the auditory system during speech planning and to develop a theoretical framework for how the CNS prepares for effective auditory monitoring before speech onset. Prior work from our lab has shown that motor predictions can modulate auditory processing even before speech initiation—referred to as pre-speech auditory modulation (Daliri & Max, 2015a, 2015b, 2018). We hypothesize that the CNS employs an active mechanism whereby motor predictions fine-tune the auditory system in a speech-specific manner to enhance monitoring efficiency. We conducted a pilot study (n = 7) using electroencephalography (EEG) and speech acoustics in a novel experimental paradigm to test this. Participants sat in a sound-attenuated room and completed five blocks of speech production and silent reading conditions. Each trial began with a fixation cross presented for 500 ms, followed by the display of a word in white text. In 75% of the trials, a brief auditory stimulus (subject-specific /ε/ or /æ/, 40 ms duration, 75 dB SPL) was presented 400 ms after word onset. Then, 200 ms later, the word changed from white to green, serving as the “go” cue for participants to produce the word. In the silent reading condition, participants viewed and read the word silently without vocalizing. No auditory stimulus was delivered in the remaining 25% of trials (no-audio trials). We recorded event-related potentials (ERPs) in response to the auditory stimuli presented during speech planning or silent reading. The stimuli were either congruent with the planned word (e.g., /ε/ before producing /εd/) or incongruent (e.g., /æ/ before producing /εd/). After removing baseline responses using no-audio trials, we measured the N1-P2 peak-to-peak amplitude (70–250 ms) as an index of auditory responsiveness. We then calculated pre-speech auditory modulation by subtracting ERP amplitudes in the speech condition from those in the reading condition. Results revealed significantly greater pre-speech modulation in congruent trials than incongruent trials, suggesting that the auditory system is fine-tuned speech-specific during planning. These findings suggest that the CNS engages in predictive, speech-specific auditory modulation before speech initiation. This work challenges current models of speech production and lays the groundwork for understanding how preparatory neural mechanisms support fluent speech. This work was supported by a New Investigator Grant from the Arizona Biomedical Research Centre (RFGA2024-022-018) and an ISSR Seed Grant from Arizona State University, both awarded to Yaser Merrikhi.
Topic Areas: Speech Motor Control,