A common somaesthetic pathway to red nucleus and motor cortex

Area of Science:

• Neuroscience
• Motor Control
• Somatosensory System

Background:

• Short latency somatosensory responses are observed in both the red nucleus and motor cortex.
• A ventral spinal ascending pathway has been previously implicated in red nucleus responses.

Purpose of the Study:

• To investigate if the same ventral spinal pathway transmits short latency somatosensory inputs to the motor cortex.
• To elucidate the neural pathways involved in rapid sensory feedback to motor structures.

Main Methods:

• Utilized the collision technique to trace neuronal pathways.
• Performed intracellular recordings from identified corticospinal cells in acutely prepared cats.
• Ablated specific spinal cord tracts (brachium conjunctivum, dorsal columns) and cortical connections to isolate pathways.

Main Results:

• Demonstrated that somatosensory responses in red nucleus cells are transmitted via collaterals of ascending fibers terminating in the ventrobasal thalamus.
• Confirmed the presence of postsynaptic potentials in corticospinal cells following dorsal column stimulation, even after extensive pathway ablations.
• Identified parallel somatosensory input pathways to both rubrospinal and corticospinal cells.

Conclusions:

• The findings support the existence of parallel somatosensory input pathways to the red nucleus and motor cortex.
• These parallel pathways likely originate from a common ventral spinal ascending system.
• This organization suggests a mechanism for on-line correction of ongoing movements based on sensory feedback.