Post-Movement Beta Activity in Sensorimotor Cortex Indexes Confidence in the Estimations from Internal Models.

Tan H
Wade C
Brown P

Experience can make us confident in our actions, whereas novel settings require adjustment of previously successful movements. We explored how the brain organises whether movements can be repeated or need more refining. We found that a particular set of brain waves reflect how certain we are that movements will achieve their goal when repeated, and can also promote the changing of movement plans.

Scientific Abstract

Beta oscillations are a dominant feature of the sensorimotor system. A transient and prominent increase in beta oscillations is consistently observed across the sensorimotor cortical-basal ganglia network after cessation of voluntary movement: the post-movement beta synchronization (PMBS). Current theories about the function of the PMBS have been focused on either the closure of motor response or the processing of sensory afferance. Computational models of sensorimotor control have emphasized the importance of the integration between feedforward estimation and sensory feedback, and therefore the putative motor and sensory functions of beta oscillations may reciprocally interact with each other and in fact be indissociable. Here we show that the amplitude of sensorimotor PMBS is modulated by the history of visual feedback of task-relevant errors, and negatively correlated with the trial-to-trial exploratory adjustment in a sensorimotor adaptation task in young healthy human subjects. The PMBS also negatively correlated with the uncertainty associated with the feedforward estimation, which was recursively updated in light of new sensory feedback, as identified by a Bayesian learning model. These results reconcile the two opposing motor and sensory views of the function of PMBS, and suggest a unifying theory in which PMBS indexes the confidence in internal feedforward estimation in Bayesian sensorimotor integration. Its amplitude simultaneously reflects cortical sensory processing and signals the need for maintenance or adaptation of the motor output, and if necessary, exploration to identify an altered sensorimotor transformation.

Post-Movement Beta Activity in Sensorimotor Cortex Indexes Confidence in the Estimations from Internal Models.
Electroencephalogram (EEG) waves were recorded while subjects moved a hand-held joystick to move a cursor to a jumping target on a computer screen. Average time-evolving EEG spectra are shown. Two experimental conditions were tested, which only differed in terms of whether the first ‘priming’ stage of each condition involved the interposition of random angles between the joy-stick and cursor (random priming, upper panels) or no angle (stable priming, lower panels). In the second ‘adaptation’ stage of each condition a fixed angle was interposed between the joy-stick and cursor. The effect of this manipulation was then ‘washed-out’ in the third phase. Joystick movement occurred at time zero, and was followed by an increase in the power of cortical beta oscillations. This increase was less when the priming phase involved random joystick-cursor perturbation angles, as the value of the motor plan used to perform each last joystick movement was uncertain (contrast the red blobs after the movement in the upper and lower panels towards the end of the priming stage). Conversely the value of the motor plan used to perform the last joystick movement became much more uncertain when stable priming was first followed by a fixed angle interposed between the joy-stick and cursor in the second ‘adaptation’ phase (contrast the red blobs after the movement in the lower panel towards the end of the priming stage with that at the beginning of the adaptation stage).
Citation
2016.J. Neurosci., 36(5):1516-28.
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