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 unclear.

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 thalamic connectivity.

Main Methods:

• In vitro electrophysiology
• Optogenetics
• Retrograde labeling in mice (either sex)

Main Results:

• vM1 inputs selectively target L6 CT neurons projecting to both VPm and POm nuclei more strongly than those projecting only to VPm.
• Dual-projecting CT neurons exhibit greater responsiveness due to distinct intrinsic membrane properties and synaptic mechanisms.
• vS1 comprises at least two discrete L6 CT subcircuits with unique projection patterns, physiology, and vM1 connectivity.

Conclusions:

• vS1 contains distinct L6 CT subcircuits differentiated by thalamic targets and motor cortex connectivity.
• These findings offer insights into how specific CT subcircuits may modulate tactile sensory signals in the thalamus during active whisking.