Distinct temporal activity patterns in the rat M1 and red nucleus during skilled versus unskilled limb movement

Area of Science:

• Neuroscience
• Motor Control
• Systems Neuroscience

Background:

• Mammalian motor systems utilize interconnected supraspinal networks.
• The distinct roles of these networks in movement production remain unclear, especially in primates due to their fused activity.

Purpose of the Study:

• To investigate if task context and using a phylogenetically older mammal (rats) can differentiate supraspinal network contributions.
• To compare neural activity in the motor cortex (M1) and magnocellular red nucleus (mRN) during distinct forelimb tasks in rats.

Main Methods:

• Simultaneous multi-single neuron recordings from M1 and mRN in rats.
• Analysis of neural activity during two kinematically similar but contextually different forelimb tasks: skilled reaching and treadmill locomotion.

Main Results:

• During locomotion, both M1 and mRN showed similar neuronal firing patterns related to swing phase onset and end.
• During skilled reaching, distinct temporal activity patterns emerged: mRN neurons peaked mid-reach, while M1 neurons showed elevated activity during initial and terminal phases.

Conclusions:

• Motor-behavioral context can modulate overlapping activity within supraspinal sensorimotor networks.
• The rubral complex (mRN) may play a key role in adapting muscle synergies for novel tasks, complementing cortical learning.