Distinct Functional Modules for Discrete and Rhythmic Forelimb Movements in the Mouse Motor Cortex.

Area of Science:

• Neuroscience
• Motor Control
• Systems Neuroscience

Background:

• Animal movements exhibit discrete and rhythmic dynamics, processed differently by the central nervous system (CNS).
• The precise cortical representation of these distinct movement dynamics remains largely unclear.

Purpose of the Study:

• To investigate the cerebral cortex's representation of movement dynamics.
• To map functional modules for discrete and rhythmic forelimb movements using prolonged transcranial optogenetic stimulation (pTOS).

Main Methods:

• Developed and utilized prolonged transcranial optogenetic stimulation (pTOS) in awake, channelrhodopsin-2 transgenic mice.
• Investigated cortical domains inducing discrete (forward/backward) and rhythmic forelimb movements.
• Analyzed intracortical connections, spinal projections, and cross-domain neuronal interactions.

Main Results:

• Identified distinct cortical domains for forward/backward discrete and rhythmic forelimb movements.
• Demonstrated that each domain possesses intrinsic velocity/oscillation profiles and internal connectivity.
• Showed that these domains mutually inhibit each other and can induce ethologically relevant movements, adapting to environmental constraints like lever-pulling.

Conclusions:

• The motor cortex contains specialized functional modules for discrete and rhythmic movement dynamics.
• These motor modules exhibit plasticity, adapting to environmental contexts to produce purposeful behaviors.
• Cortical organization supports distinct movement types and their flexible adaptation.