Cortical beta coherence provides a stronger non-invasive predictor of movement vigor than local beta power

Abstract

BackgroundMovement elicits a robust decrease in motor cortical beta-band ({beta}; 13-30 Hz) power contralateral to the moving limb. On this basis, studies have targeted contralateral motor cortical {beta} power to decode or modulate movement vigor (initiation and execution speed) non-invasively. Yet, reported behavioral effects and decoding accuracy remain modest. Considering that controlling vigor involves distributed brain regions, network-level metrics that capture interactions between cortical regions may track changes in vigor more accurately than local power. We therefore tested whether {beta} cortico-cortical coherence, measured as functional connectivity between contralateral motor cortex and other cortical areas, predicts movement vigor more reliably than {beta} power. MethodsThirty healthy participants performed right hand opening at two instructed speeds (Fast, Slow), while high-density electroencephalography (EEG) was recorded. EEG data were source-localized, and analyses were conducted at the sensor and source levels. We compared {beta} power and {beta} coherence in their ability to discriminate Fast from Slow condition. Effects were assessed across the whole scalp/cortex and using subject-specific selections of electrodes/parcels optimized for discrimination. ResultsFast trials exhibited shorter movement time (MT) and reaction time (RT) than Slow trials, indicating higher vigor. No electrodes cluster showed any significant {beta} power difference between Fast and Slow conditions. With subject-specific channel selection, {beta} power discriminated vigor above chance in most participants, but the polarity of the {beta} power contrast (Fast < Slow or Fast > Slow) varied across individuals. In contrast, with subject-specific parcel selection, {beta} coherence was consistently reduced during Fast relative to Slow in the majority of participants. Across participants, lower {beta} coherence, but not {beta} power, was significantly associated with larger Slow-Fast vigor difference. Conclusions{beta} cortico-cortical coherence between contralateral motor cortex and other cortical regions provided a more robust and consistent predictor of movement vigor than contralateral motor cortical {beta} power. {beta} coherence exhibited a sustained reduction during fast movements across trials and participants, supporting its use as target for non-invasive neuromodulation of vigor and as feature for decoding intended movement speed.