Motor Control of Distinct Layer 6 Corticothalamic Feedback Circuits

Area of Science:

• Neuroscience
• Sensory Processing
• Cortical Circuits

Background:

• Layer 6 corticothalamic (L6 CT) neurons provide feedback to the thalamus, influencing sensory input.
• The functional role and control mechanisms of this feedback, especially concerning distinct CT neuron populations, remain poorly understood.

Purpose of the Study:

• To investigate how the vibrissal primary motor cortex (vM1) influences different L6 CT neuron subcircuits in the vibrissal primary somatosensory cortex (vS1).
• To determine if vM1 control is specific to CT neurons with distinct intrathalamic projections.

Main Methods:

• In vitro electrophysiology
• Optogenetics
• Retrograde labeling in mice (either sex)
• Analysis of vM1 inputs on vS1 L6 CT neurons

Main Results:

• vM1 inputs selectively target L6 CT neurons based on their thalamic projections.
• Dual VPm/POm-projecting CT neurons in lower L6a showed stronger responses to vM1 input than VPm-only projecting neurons in upper L6a.
• Differences in intrinsic membrane properties and synaptic mechanisms underlie the selective responsiveness.

Conclusions:

• vS1 contains at least two distinct L6 CT subcircuits defined by thalamic connectivity, intrinsic physiology, and vM1 functional connectivity.
• These findings offer insights into how specific CT subcircuits may modulate tactile sensory signals in the thalamus during active whisking.