Poster B5, Thursday, August 16, 3:05 – 4:50 pm, Room 2000AB
Changes in sensorimotor control of speech observed in oscillations of the EEG mu rhythm
Tim Saltuklaroglu1, Ashley Harkrider1, Tiffani Kittilstved1, David Thornton1, David Jenson1;1University of Tennessee Health Sciences Center
Background: The EEG mu rhythm is a sensorimotor rhythm characterized by peaks in alpha (8-13 Hz) and beta (15-25 Hz) that are sensitive to aspects of internal modeling. During movement, alpha activity may reflect sensory to motor feedback, while beta activity captures motor to sensory projections (i.e., forward models). As such, mu rhythms represent changes in sensorimotor control imparted by exogenous and endogenous speech manipulations. Stuttering is characterized by sensorimotor dysfunction related to internal modeling deficits. These deficits can be overcome temporarily by exogenous and endogenous manipulations that alter sensorimotor control to improve fluency. Such manipulations clearly alter sensorimotor control. However, it is not clear how they impact neurotypical speakers with respect to internal modeling mechanisms and changes to feedforward/feedback motor control contributions over the time course of utterances. Thus, the purpose of this study was to determine whether changes in sensorimotor control resulting from speaking conditions that induce fluency in people who stutter (PWS) can be measured using electroencephalographic (EEG) mu rhythms in neurotypical (non-stuttering) speakers. Methods: Neurotypical adults spoke in one control condition (solo speaking) and four experimental conditions that exogenously or endogenously manipulated sensorimotor control [choral speech, delayed auditory feedback (DAF), prolonged speech and pseudostuttering]. Independent component analysis (ICA) was used to identify sensorimotor mu and perilabial EMG components from EEG recordings. Time-frequency analyses measured μ-alpha and mu-beta event-related synchronization (ERS) and desynchronization (ERD), alongside EMG activity, during each speech condition. Results: 19/24 participants contributed mu components. Relative to the control condition, the choral and DAF (exogenous) conditions elicited increases in μ-alpha ERD in the right hemisphere. In the pseudostuttering (endogenous) condition, increases in μ-beta ERD were observed in the left hemisphere. No differences were present between the prolonged (endogenous) speech and control conditions. Strongest mu activity coincided with EMG activity (i.e.., during speech production), beginning about 300 ms following the cue to speak. Conclusions: Differences observed in the experimental conditions are thought to reflect sensorimotor control changes. Increases in right hemisphere μ-alpha ERD likely reflect increased reliance on auditory feedback during the choral and DAF conditions. This finding provides further evidence that mu-alpha activity captures sensory-to-motor feedback during movement tasks and exogenous speech manipulations induce stronger feedback control. In the left hemisphere, increases in μ-beta ERD during pseudostuttering suggest stronger activation of forward models, possibly due to syllable repetitions that strengthen sensory predictions and the novelty of the task. Significance: Changes in sensorimotor control related to feedforward and feedback control in fluency-enhancing speech manipulations can be measured using time-frequency decompositions of EEG μ rhythms in neurotypical speakers. This quiet, non-invasive, and temporally sensitive technique may be applied to learn more about normal sensorimotor control and fluency enhancement in persons who stutter.
Topic Area: Speech Motor Control and Sensorimotor Integration