Thalamocortical Axonal Activity in Motor Cortex Exhibits Layer-Specific Dynamics during Motor Learning

Area of Science:

• Neuroscience
• Motor Control
• Systems Neuroscience

Background:

• The thalamus acts as a critical relay for neural signals from the basal ganglia and cerebellum to the neocortex.
• Thalamocortical axonal activity patterns during the dynamic process of motor learning are not well understood.

Purpose of the Study:

• To investigate layer-specific thalamocortical axonal activity in the motor cortex during a motor learning task.
• To elucidate the roles of the basal ganglia and cerebellum in modulating this activity.

Main Methods:

• Two-photon calcium imaging of thalamocortical axons in the mouse motor cortex.
• Mice were trained on a self-initiated lever-pull task.
• Selective stimulation of substantia nigra pars reticulata and deep cerebellar nuclei (DCN).
• Lesion studies targeting the dorsal striatum and DCN.

Main Results:

• Layer 1 (L1) axons showed activity at both initiation and termination of the lever-pull, while Layer 3 (L3) axons were active at initiation.
• L1 population activity exhibited sequential patterns correlated with lever-pull duration and reproducibility.
• Substantia nigra pars reticulata stimulation preferentially activated L1 axons, whereas DCN stimulation activated L3 axons.
• Disruptions in the dorsal striatum or DCN impaired motor learning and altered temporal dynamics in both L1 and L3 axons.

Conclusions:

• Layer-specific thalamocortical signals dynamically change during motor skill acquisition.
• Both basal ganglia and cerebellar pathways are essential for motor learning and the observed temporal dynamics in thalamocortical activity.