A Cortico-Cortical Pathway Targets Inhibitory Interneurons and Modulates Paw Movement during Locomotion in Mice.

Area of Science:

• Neuroscience
• Motor Control
• Somatosensory System

Background:

• The primary somatosensory cortex (S1) is vital for movement control, processing sensory input during locomotion.
• While the vibrissal S1 area's role is known, non-whisker S1 involvement in movement is less understood.
• S1 receives organized inputs from sensorimotor areas like secondary somatosensory cortex (S2) and primary motor cortex (M1).

Purpose of the Study:

• To investigate the role of non-whisker S1 areas and their corticocortical connections in controlling hind paw movement during locomotion.
• To determine how S2 and M1 inputs to non-whisker S1 influence locomotion.
• To elucidate the neural circuitry underlying S2-S1 interactions in movement control.

Main Methods:

• Unilateral silencing of non-whisker S1 areas in male and female mice.
• Behavioral assays including rotarod and runway locomotion tests.
• Patch-clamp recordings in brain slices to analyze S2 projections to S1 interneurons.
• Circuit-mapping techniques.

Main Results:

• Silencing non-whisker S1 disrupted hind paw movement during locomotion.
• Disruption of S2→non-whisker S1 projections altered hind paw orientation during locomotion.
• S2 projections to S1 preferentially innervated inhibitory interneuron subtypes.
• M1 projection manipulation had minimal effect on locomotion.

Conclusions:

• Interneuron-mediated S2-S1 corticocortical interactions are critical for efficient locomotion.
• This study uncovers a novel corticocortical circuit in S1 regulating paw orientation during walking.
• The findings highlight the importance of non-whisker S1 in motor control through specific S2 inputs.