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Poster D9, Friday, August 17, 4:45 – 6:30 pm, Room 2000AB

Stuttering-related differences in auditory-motor coherence in speech and tone discrimination.

Tim Saltuklaroglu1, Ashley Harkrider1, David Jenson1, David Thornton1;1University of Tennessee Health Sciences Center

Background: Sensorimotor processing across the dorsal stream is thought to be disrupted in people who stutter (PWS) due to compromised internal modeling mechanisms. However, the nature of the deficit remains unclear and investigation of sensorimotor dynamics in speech production is problematic due to the potentially contaminating effects of stuttering behaviors. Therefore, speech and tone discrimination tasks, also known to recruit sensorimotor regions for internal modeling, may be used to access these mechanisms. Independent component analysis of raw EEG data can identify mu rhythms with characteristic alpha (8-13 Hz) and beta (15-25 Hz) spectral peaks that emanate from anterior dorsal (pre/primary motor regions). In addition, tau rhythms with a characteristic alpha spectral peak emanate from posterior auditory (superior temporal gyrus) regions. Time-frequency analysis can be applied to these rhythms to examine changes in oscillatory power in a given region. Also, phase coherence measures establish oscillatory synchronization of the rhythms as an indicator of connectivity. Compared to non-stuttering participants, PWS are expected to produce time-frequency differences in mu and tau rhythms and different patterns of auditory-motor coherence. Methods Raw EEG recording were made from 27 PWS and matched non-stuttering adults in a control condition (passive listening to noise) and four discrimination conditions: 1) tones in a quiet background, 2) tones in a noisy background, 3) speech in a quiet background, and 4) speech in a noisy background. Independent component analysis identified mu and tau components. Time-frequency analysis via event-related spectral perturbations identified patterns of anterior and posterior dorsal stream activity in mu and tau rhythms respectively across the time course of events. Phase coherence measures between mu and tau rhythms were calculated using the EEGLAB newcrossf for subjects who contributed both mu and tau components. Statistical comparisons were performed with permutation statistics (2000 permutations). Results All participants achieved over 95% discrimination accuracy and only data from correct discriminations were used in the EEG analysis. In addition to time-frequency differences observed in mu rhythms (Saltuklaroglu, et al., 2017), PWS display increased peri-stimulus event-related dysynchronization by reduced post-stimulus alpha event-related synchronization in auditory components. In addition, PWS demonstrate elevated mu to auditory phase coherence in the alpha band, which is more robust in the presence of noise. Discussion Mu rhythm data indicate that PWS show increased sensorimotor activity when passively listening to noise and have reduced capacity for inhibiting noise when discriminating (Saltuklaroglu, et al., 2017). Tau rhythm data suggest that auditory stimuli are covertly replayed following discrimination, which produces a form of speech-induced suppression. This suppression is reduced in PWS. Coherence data indicate that PWS demonstrate abnormally elevated coherence between sensorimotor mu and auditory tau alpha rhythms. Together, these findings suggest aberrant sensorimotor function across the time course of perceptual events, providing temporally sensitive evidence that sensorimotor dysfunction associated with stuttering may subtly affect cognitive processes in addition to speech production.

Topic Area: Speech Motor Control and Sensorimotor Integration