Brainstem neurons that command mammalian locomotor asymmetries

Area of Science:

• Neuroscience
• Motor Control
• Locomotion

Background:

• Locomotion relies on descending command neurons for gait and speed, which are typically symmetric.
• Asymmetric movements, like turning left or right, are controlled by an unknown system.
• Understanding directional control is crucial for deciphering complex motor behaviors.

Purpose of the Study:

• To identify the neural circuits responsible for controlling left-right locomotor direction in mammals.
• To investigate the role of Chx10-lineage neurons in directional movement control.
• To elucidate the mechanisms by which directional commands are relayed to spinal circuits.

Main Methods:

• Selective unilateral activation and inhibition of Chx10-lineage reticulospinal neurons in freely moving mice.
• Paired left-right motor recordings to analyze limb and axial spinal circuit activity.
• Identification of upstream sensorimotor brain regions projecting to Chx10 neurons.

Main Results:

• Chx10-lineage reticulospinal neurons primarily project ipsilaterally.
• Unilateral activation of Chx10 neurons induces ipsilateral turning.
• Unilateral inhibition of Chx10 neurons results in contralateral turning.
• Distinct spinal mechanisms mediate directional movements via limb and axial circuits.
• Unilateral activation of upstream brain regions influences Chx10 neuron activity and directional commands.

Conclusions:

• Chx10-lineage reticulospinal neurons are essential for commanding left-right locomotor asymmetries.
• This study identifies a novel descending motor system controlling directional turning in mammals.
• The findings provide insights into the neural basis of asymmetric motor behaviors.