Preparative activities in posterior parietal cortex for self-paced movement in monkeys

Area of Science:

• Neuroscience
• Motor Control
• Electrophysiology

Background:

• Voluntary movements are initiated by internal stimuli, but the precise neural mechanisms are not fully understood.
• The posterior parietal cortex is implicated in sensorimotor integration and planning, but its role in movement preparation requires further elucidation.

Purpose of the Study:

• To investigate the involvement of the posterior parietal cortex in the preparation of self-paced movements.
• To identify the temporal dynamics and somatotopic organization of cortical activity preceding voluntary actions.

Main Methods:

• Chronic electrode implantation on the surface and at depth (2.0-3.0 mm) in various cortical areas of monkeys.
• Recording of cortical field potentials during self-paced finger, toe, mouth, hand, and trunk movements.
• Analysis of surface-negative, depth-positive potentials (readiness potential) in relation to movement onset.

Main Results:

• A readiness potential was consistently observed in the posterior parietal cortex approximately 1.0 second before the onset of all tested self-paced movements.
• Similar readiness potentials were detected in the premotor, motor, and somatosensory cortices.
• Somatotopic organization of the readiness potential was evident in the posterior parietal cortex, though less distinct than in motor and somatosensory areas.

Conclusions:

• The posterior parietal cortex is critically involved in the preparation of self-paced voluntary movements across different body parts.
• These findings highlight the posterior parietal cortex as a crucial component of the central nervous system network underlying internally initiated actions.
• The study provides insights into the neural basis of voluntary movement initiation and preparation.