Movement initiation and grasp representation in premotor and primary motor cortex mirror neurons

Area of Science:

• Neuroscience
• Motor Control
• Primate Brain Function

Background:

• Pyramidal tract neurons (PTNs) in macaque rostral ventral premotor cortex (F5) and primary motor cortex (M1) are crucial for skilled movement.
• PTNs are known to be active during movement execution.
• Recent findings suggest PTN activity during action observation, even without movement, but a population-level understanding is lacking.

Purpose of the Study:

• To investigate the population-level activity of PTNs in F5 and M1 during action execution, observation, and withholding (NoGo).
• To understand the distinct roles of M1 and F5 in representing actions during different behavioral contexts.

Main Methods:

• Single-neuron recordings were performed in M1 (n=187) and F5 (n=115) of two adult male macaques.
• Neural activity was recorded during executed, observed, and withheld (NoGo) reach-to-grasp actions.

Main Results:

• F5 neurons showed similar representations of grasping actions during both execution and observation.
• M1 population activity during observation was distinct from execution and more aligned with NoGo activity.
• Individual M1 neurons were active during observation, but population activity suggested a role in withholding self-movement.

Conclusions:

• M1 and F5 exhibit differential roles in action representation during observation.
• M1 activity during observation may contribute to withholding self-movement rather than action execution.
• M1 may dissociate movement initiation from grasp representation for flexible behavioral guidance.