Abstract
Volitional limb motor control involves dynamic and static muscle actions. It remains elusive how such distinct actions are controlled through separated or shared neural circuits. Here we explored the potential separation for dynamic and static controls in primate hand actions, by investigating the neuronal coherence between local field potentials (LFPs) of the spinal cord and the forelimb electromyographic activity (EMGs), and LFPs of the motor cortex and the EMGs during the performance of a precision grip in macaque monkeys. We observed the emergence of beta-range coherence with EMGs at spinal cord and motor cortex in the separated phases; spinal coherence during the grip phase and cortical coherence during the hold phase. Further, both of the coherences were influenced by bidirectional interactions with reasonable latencies as beta oscillatory cycles. These results indicate that dedicated feedback circuits comprising spinal and cortical structures underlie dynamic and static controls of dexterous hand actions.
Highlights
Volitional limb motor control involves dynamic and static muscle actions
If an local field potentials (LFPs)–EMG coherence manifesting exclusively during the dynamic phase could be demonstrated in the limb-related motor structure, it could provide an important step in the elucidation for specialized processes in limb control
It has been unclear whether distinct circuits are engaged in dynamic vs. static control of limb muscle actions
Summary
Volitional limb motor control involves dynamic and static muscle actions. It remains elusive how such distinct actions are controlled through separated or shared neural circuits. We observed the emergence of beta-range coherence with EMGs at spinal cord and motor cortex in the separated phases; spinal coherence during the grip phase and cortical coherence during the hold phase Both of the coherences were influenced by bidirectional interactions with reasonable latencies as beta oscillatory cycles. These results indicate that dedicated feedback circuits comprising spinal and cortical structures underlie dynamic and static controls of dexterous hand actions. Specialized processes and underlying neural circuits have been demonstrated in the primate brainstem for the dynamic and static control of saccadic eye movement[2,3] It remains unknown whether dedicated circuits for skeletomotor control are at work. If an LFP–EMG coherence manifesting exclusively during the dynamic phase could be demonstrated in the limb-related motor structure, it could provide an important step in the elucidation for specialized processes in limb control
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