Task-related changes in sensorimotor integration influence the common synaptic input to motor neurones

Area of Science:

• Neuroscience
• Motor Control
• Human Physiology

Background:

• Visual information is crucial for guiding motor actions.
• The neural control of muscle force involves complex interactions between motor commands and sensory feedback.
• Understanding how visual feedback modulates neural activity is key to optimizing motor performance.

Purpose of the Study:

• To investigate the influence of visual feedback sensitivity on the neural drive to muscles.
• To examine how visual feedback affects the frequency content of neural signals controlling muscle activity.
• To determine the impact of visual feedback on the gain of afferent feedback mechanisms.

Main Methods:

• Isometric contractions of the tibialis anterior muscle were maintained at 10% maximum voluntary contraction.
• Two visual feedback conditions were employed: high-sensitivity and low-sensitivity.
• Measurements included force tremor, Hoffmann reflex (H-reflex) amplitudes, and motor unit coherence using high-density EMG.

Main Results:

• High-sensitivity feedback led to reduced force error but increased force tremor (4-12 Hz) and H-reflex amplitudes.
• High-sensitivity feedback decreased low-frequency (1-5 Hz) motor unit coherence.
• Conversely, high-sensitivity feedback increased high-frequency coherence (6-12 Hz, ~20 Hz, >30 Hz).

Conclusions:

• Visual feedback sensitivity significantly alters the frequency spectrum of neural input to motor neurons.
• Changes in afferent feedback gain are influenced by visual feedback manipulation.
• Task-related modulation of afferent feedback likely underlies observed changes in neural drive to muscles.