Objective: Movement initiation and termination are often studied in isolation. Here we shed light on the neural processes underlying rapid changes of ongoing movements, where both processes occur nearly simultaneously.

Background: Beta-band oscillations in cortico-gasal ganglia loops are closely linked to motor behavior. Beta power decreases before movement onset (movement-related beta desynchronization; MRBD) and increases after movement termination (post-movement beta rebound; PMBR) before returning to baseline levels. Hence, movement-related beta-band dynamics are conceptualized as a sequence of amplitude modulations.

Method: We combined magnetoencephalography (MEG) and local field potential (LFP) recordings from the subthalamic nucleus (STN) in Parkinson’s patients to study beta dynamics during initiation, stopping and rapid reversal of rotational movements. The timing of the action prompts was manipulated in two separate blocks to be temporally predictable or unpredictable.

Results: We found that MRBD and PMBR have distinct spatio-spectral profiles. PMBR was more lateralized to the hemisphere contralateral to movement and had a higher peak frequency than MRBD. During reversals, the relative strength of start- and stop-related MRBD and PMBR predicted reversal-related beta activity changes, likely due to linear superimposition. The temporal overlap resulted in partial cancellation of MRBD and PMBR in primary motor cortex (MC) contralateral to the moving hand, whereas the suppression dominated the rebound on the ipsilateral side. Individual patterns of STN beta dynamics during reversals could also be predicted from superimposed stop- and start-dynamics. While MC-STN beta coherence decreased during movement initiation bilaterally, reversal and stopping were accompanied by an increase in beta coherence. Unpredictable movement prompts were associated with higher levels of coherence.

Conclusion: Our findings provide first evidence that the beta “rebound” does not need to follow suppression. Instead, beta suppression and “rebound” can overlap in time, indicating independent processes. The modulations of MC-STN beta coherence observed during movement termination and reversal suggest a role of subcortico-cortical coupling in post-movement processing, particularly when an unpredictable movement context necessitates cautious behavior.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/beta-is-jumping-the-queue-temporal-overlap-of-beta-desynchronization-and-synchronization-during-rapid-movement-changes/