Differential neural correlates of reciprocal activation and cocontraction control in dorsal and ventral premotor cortices

Area of Science:

• Neuroscience
• Motor Control
• Human Physiology

Background:

• Skillful motor actions require precise control over muscle force and impedance.
• The neural mechanisms underlying the control of force versus co-contraction using the same muscles remain poorly understood.
• Investigating whether control originates at the single muscle level or involves higher-order brain centers is crucial.

Purpose of the Study:

• To elucidate the distinct neural pathways controlling voluntary wrist torque and co-contraction.
• To determine if specific brain regions are dedicated to force control versus impedance control.
• To differentiate the roles of premotor cortex subregions in motor command generation.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was employed during voluntary isometric wrist contractions.
• Participants performed tasks requiring control of either wrist torque or muscle co-contraction.
• Online electromyogram (EMG) feedback was utilized to monitor and guide muscle activity.

Main Results:

• Blood oxygen level-dependent (BOLD) activity in the caudo-dorsal premotor cortex (PMd) correlated with wrist torque.
• BOLD activity in the ventral premotor cortex (PMv) correlated with the level of muscle co-contraction.
• These findings indicate differential activation patterns in premotor areas based on motor control strategy.

Conclusions:

• The dorsal premotor cortex (PMd) plays a distinct role in the voluntary control of muscle force (torque).
• The ventral premotor cortex (PMv) is differentially involved in controlling muscle co-contraction for impedance.
• These results suggest specialized neural circuits within the premotor cortex for distinct aspects of motor control.