Beta Oscillations and Pupil-Linked Arousal Regulate the Updating of Cognitive Models.

The beta rhythm (neural oscillations in the range 13-30 Hz) is associated with the control of movement. Discrete movements (such as a button press) are bounded by a premovement dip in beta power and a postmovement beta rebound, which are thought to release and terminate the action, respectively. However, an additional or alternative role has been suggested for the beta rebound in regulating the extent to which sensory feedback updates the task model. Using EEG and pupillometry in human volunteers of both sexes, we developed a task that dissociates updating of a cognitive model from motor control. We found that beta oscillations were modulated in two independent modes-phasic and tonic-with distinct computational correlates. When abstract task models are updated by integrating the outcomes of several actions, there is a tonic suppression of the beta rhythm, which originates at the time of the postmovement rebound, spans multiple trials, and is measurable at both the pre- and postmovement stages. Independently, phasic trial-to-trial fluctuations in beta power, primarily measurable in the premovement phase, were associated with motor readiness. The decrease in tonic beta power during model updating was mediated by an increase in tonic pupil dilation, a known correlate of model updating often considered a proxy for neuromodulatory tone.