Extrinsic and intrinsic dynamics in movement intermittency

Area of Science:

• Motor Neuroscience
• Systems Neuroscience
• Computational Neuroscience

Background:

• Motor control research typically examines intrinsic motor circuit properties or extrinsic sensorimotor feedback independently.
• Understanding how these two aspects interact is crucial for explaining complex movement behaviors.

Purpose of the Study:

• To investigate the interplay between intrinsic motor dynamics and extrinsic feedback in continuous tracking movements.
• To explain the observed intermittency in human tracking movements.

Main Methods:

• Utilized spatiotemporal perturbations in human participants during continuous tracking tasks.
• Recorded local field potentials in the motor cortex of monkeys during similar tasks.
• Analyzed data within the framework of optimal feedback control theory.

Main Results:

• Human tracking movements exhibit intermittency explained by the constructive interference of motor errors and feedback corrections.
• These corrections are filtered by the motor system's intrinsic circuitry, creating submovements at 2-3 Hz.
• Monkey motor cortex activity showed signatures of a Kalman filter, generating low-frequency oscillations during movement and delta oscillations during sleep.

Conclusions:

• The interplay of intrinsic and extrinsic dynamics is essential for explaining continuous tracking movement intermittency.
• Motor cortical networks' intrinsic rhythmicity may represent an internal model for state estimation in feedback-guided movement.
• Findings support optimal feedback control principles in motor neuroscience.