Poster A102, Saturday, March 25, 5:00 – 7:00 pm, Pacific Concourse
Distinct Neural Mechanisms for Correcting Increases and Decreases in Asynchrony During Sensorimotor Synchronization
Kelly Jantzen1, Rachel Walls1, McKaila Leytze1, Elisabeth Amir-Brownstein1, Andrew Jaye1, Kathleen Lucier1, Sarah Martinez1, McNeel Jantzen1; 1Western Washington University
Sensorimotor coordination is mediated by distributed cortical systems for maintaining a tight coupling between action and the environment in the presence of internally and externally generated errors. Recent work provides clues that different cortical mechanisms may be employed when correcting for errors that increase tap-tone asynchrony compared to those that decrease it, that is for shortening and lengthening tap intervals. We tested this hypothesis directly using EEG and TMS in three separate experiments. In each experiment we evaluated error detection and correction by systematically introduced positive and negative phase shift perturbations that were either liminal (10%) or subliminal (3%, EEG experiment only). Three main EEG findings support our hypothesis. First, a theta band response indicative of error detection and top down control was observed in frontal-medial pre-SMA and anterior cingulate only for liminal positive perturbations. Second, we observed an increase in theta band coupling between SMA and contralateral motor cortex exclusively for positive perturbations suggesting a top down modulation of motor parameters required to lengthening tap intervals. Third, when compared to other conditions, liminal positive perturbations result in an increase in post movement beta rebound – a signature of inactivity – within contralateral primary motor cortex. This latter finding was supported by follow up TMS studies showing reduced excitability and increased short intracortical inhibition of motor cortex for positive perturbations. We propose that fronto-medial motor areas exert a top down inhibitory influence over primary motor cortex to effectively lengthen tap intervals in response to lengthening tap-tone asynchronies.
Topic Area: PERCEPTION & ACTION: Motor control