Speaker
Description
Several TMS investigations have demonstrated that action observation (AO) exerts a facilitatory effect on corticospinal excitability (CSE). In a large-scale study involving over 100 participants, we observed that AO not only increased MEP amplitude but also significantly reduced its variability. These findings suggest that the baseline variability in MEPs amplitude (when motor rhythms are synchronized) compared to the decreased variability during AO (when motor rhythms are desynchronized) may relate to the oscillatory phase of the underlying mu-rhythm. Indeed, recent studies indicate that, at rest, MEP amplitude is influenced by the phase of motor oscillations at the time of TMS delivery.
We conducted an EEG-TMS study to explore the interplay between CSE facilitation induced by AO and the estimated mu-rhythm oscillation phase at pulse delivery. Twenty-four right-handed participants received 440 TMS pulses over the left primary motor cortex across two randomized conditions: (1) observation of a black screen (REST), and (2) observation of reach-to-grasp actions (AO). Simultaneous recordings of EMG from the rFDI and 64-channel EEG were obtained.
Our analysis reveals that, during REST, MEP amplitude was modulated by mu-rhythm phase, with larger responses during the early rising phase. In contrast, during AO (when mu-rhythm is desynchronized), MEP amplitude was not affected by oscillation phase. A permutation test highlighted significantly higher MEPs amplitude during the rising phase at REST compared to a shuffled distribution. These findings may explain the greater CSE variability at REST and support the identification of reliable predictors for selecting good candidates for action observation treatment.
| If you're submitting a symposium talk, what's the symposium title? | "Advanced Applications of Noninvasive Brain Stimulation and EEG in Experimental Psychology" |
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| If you're submitting a symposium, or a talk that is part of a symposium, is this a junior symposium? | Yes |
