Whole-brain entrainment and anticipation in fMRI motor task data.

The readiness potential (RP), also known as the Bereichtschaftspotential, is commonly observed in EEG recordings as a slow build-up of negative electrical potential prior to self-directed motor movements (Kornhuber et al. 1965). In this study, we analyzed motor task-based functional magnetic resonance (fMRI) data acquired from 262 human participants, focusing on the degree of signal phase synchronization across different frequency spans and brain regions. A new method that clusters brain regions based on instantaneous phase allowed for time resolved estimation of cross-subject phase synchronization. We show that during rest periods that precede movement, an fMRI equivalent of the RP is gradually established in a network that encompasses the bilateral supplementary motor area and parts of the cingulo-opercular network, recently described as the brains Action Mode network (Dosenbach et al. 2025). Importantly, an anticipatory negative shift in the fMRI signal was observed in both single subjects and single epochs. Tongue movement elicited strong synchronization between the orbitofrontal, ventromedial, and temporal pole cortices. Our findings suggest a link between fMRI and electrophysiological recordings of anticipatory motor events in the brain. The method presented here grades brain synchronization along an in-phase and anti-phase continuum and has applications in clinical settings, as well as for cognitive brain mapping that goes beyond anticipation. Significance statementThe readiness potential (RP) is observed in EEG recordings as a slow build-up of negative electrical potential in the supplementary motor area (SMA) starting up to two seconds before self-initiated motor movements. It is believed to play a causal role in motor preparation. Given that it is only detectable by averaging 30-40 epochs, its existence as a real signal has been challenged by new modeling approaches which suggests the early RP-component is merely a summation of stochastic noise. In this study, we demonstrate that the equivalent of the RP is present in functional magnetic resonance imaging (fMRI) data in a distributed network known as the "action mode network". The RP-equivalent is present in single subjects and single epochs.