Cat hindlimb motoneurons during locomotion. II. Normal activity patterns.

Area of Science:

• Neuroscience
• Motor Control
• Locomotion Biomechanics

Background:

• Understanding the neural control of locomotion is crucial for addressing movement disorders.
• Motoneuron activity patterns during locomotion provide insights into muscle activation and movement execution.

Purpose of the Study:

• To investigate the relationship between the activity patterns of individual motoneurons and the electromyographic (EMG) activity of their target muscles during walking.
• To determine how walking speed affects motoneuron firing rates and discharge patterns.

Main Methods:

• Recorded activity from 51 lumbar motoneurons in cats walking on a treadmill at various speeds.
• Identified motoneuron target muscles using spike-triggered averaging of EMG.
• Correlated motoneuron firing rates with smoothed EMG recordings from anterior thigh muscles.

Main Results:

• Motoneurons fired a single burst per step cycle, with firing rates increasing with walking speed.
• Firing rates peaked mid-burst and generally increased with walking speed and early recruitment.
• Motoneuron firing patterns strongly correlated with the EMG activity of their target muscles, explaining 88-96% of the variance.

Conclusions:

• Individual motoneuron firing patterns are tightly coupled to the EMG activity of their specific target muscles during locomotion.
• Walking speed significantly modulates motoneuron firing rates and discharge characteristics.
• These findings highlight the precise neural encoding of motor commands for walking in cats.