Modulation of beta-range oscillatory synchrony as a mechanism for response selection

Abstract

Event Abstract Back to Event Modulation of beta-range oscillatory synchrony as a mechanism for response selection Peter Praamstra1*, B C M Van Wijk2 and A. Daffertshofer2 1 Behavioural Brain Science Centre, University of Birmingham, United Kingdom 2 Research Institute MOVE, VU University Amsterdam, Netherlands Beta range oscillatory activity recorded over the motor cortex is typically attenuated during the preparation of movement and shows a rebound after movement. Contrasting with down-regulation before voluntary movement, recent work has demonstrated that beta activity can be prospectively up-regulated when the task requires a maintained posture instead of the generation of a new movement . Likewise, in the domain of visual spatial attention there is evidence for prospective up- and down-regulation of activity in the alpha frequency band. Both these examples concern anticipatory adjustments of oscillatory activity for future events. The present investigation addressed whether concurrent up- and down-regulation of beta synchrony can act as an online mechanism implementing the selection between competing motor responses. The investigation used high-density EEG and examined both local oscillatory synchrony (beta spectral power) and long-range oscillatory synchrony in terms of corticomuscular coherence and phase synchrony. Electroencephalographic and electromyographic signals were recorded during a cued choice reaction task. Response alternatives were mapped onto opposite hands and response readiness was manipulated by directional cues that were predictive or non-predictive of the response side indicated by an upcoming response signal. Reaction times and movement-related potentials confirmed that participants used the predictive cues to prepare their response. Further analyses focused on measures of beta activity during the two-second delay period, that is, during the interval between cue and response signal. In the first second of that period, directional cues elicited lateralized power, corticospinal coherence, and phase synchronization irrespective of their predictive value. At the same time, beta activity increased in the non-predictive cue condition relative to the predictive condition. By contrast, only predictive cues resulted in response preparation during the second half of the delay period, expressed in lateralization of not only power, but also of corticospinal coherence and phase synchronization. Together, these data indicate that processing of a directional cue, whether relevant or not, is associated with covert response activation, expressed in a differential modulation of beta activity in ipsi- and contralateral motor cortex. In addition, access of this covert activation to later preparation stages seems critically influenced by beta local and long-range synchrony. We therefore conclude that up- and down-regulation of beta activity is likely to have a functional role in response selection, resembling attentional modulation of alpha activity in visual selection.