Mouse corticospinal system comprises different functional neuronal ensembles depending on their hodology

Area of Science:

• Neuroscience
• Motor Control
• Cortical Circuits

Background:

• Movement performance relies on synaptic interactions from parallel sensorimotor cortical outputs.
• Pyramidal tract neurons (PTNs) in layer 5B are key neocortical outputs to subcortical structures, including the spinal cord via the corticospinal (CS) system.
• The intracortical synaptic interactions generating CS commands and the functional organization of CS neurons remain poorly understood.

Purpose of the Study:

• To investigate the functional organization of the corticospinal (CS) system.
• To analyze the activity of identified CS neurons projecting to different spinal cord segments.
• To understand intracortical synaptic interactions underlying CS commands.

Main Methods:

• Utilized two-photon calcium imaging to monitor neuronal activity.
• Employed retrograde neuronal tracers to identify specific CS neuron populations.
• Analyzed spontaneous calcium transients in layer 5 pyramidal neurons in sensorimotor cortex slices from transgenic mice.

Main Results:

• Identified distinct subgroups of CS neurons projecting to dorsal horn and ventral spinal cord areas.
• Observed more synchronous activity within these distinct CS neuron subgroups compared to other groups.
• Demonstrated that CS neurons projecting to different spinal cord zones segregate into functional ensembles based on their projections (hodology).

Conclusions:

• CS neurons projecting to different spinal cord zones are functionally organized into distinct ensembles.
• This modular organization of CS outputs suggests a coordinated control mechanism for sensorimotor behaviors.
• Hodology-based functional segregation of CS neurons underlies coordinated motor control.