Corrective Muscle Activity Reveals Subject-Specific Sensorimotor Recalibration.

Area of Science:

• Neuroscience
• Motor Control
• Biomechanics

Background:

• Motor adaptation involves recalibrating planned and corrective actions.
• Corrective movements in locomotion are typically viewed as independent of sensorimotor recalibration.
• The role of corrective responses in indicating an adapted motor state remains unclear.

Purpose of the Study:

• To investigate if corrective motor responses reflect the adapted state after sensorimotor adaptation.
• To determine if prolonged exposure to a novel walking environment changes corrective responses.
• To explore age-related differences in motor adaptation and corrective responses.

Main Methods:

• Electromyographic (EMG) signals from 15 leg muscles were recorded before, during, and after split-belts walking.
• Split-belts walking involved asymmetrical leg speeds to induce sensorimotor adaptation.
• Corrective responses were isolated by analyzing rapid muscle activity during unexpected speed transitions.

Main Results:

• Corrective muscle activity patterns differed after short versus long split-belts walking exposure.
• Following long exposure, returning to normal walking elicited corrective responses opposite to the initial perturbation.
• Motor learning from adaptation showed a decline with age, unlike steady-state muscle activity modulation.

Conclusions:

• Corrective motor commands reflect the adapted state of the motor system.
• The motor system adapts to novel environments, treating them as the new normal.
• Motor adaptation and the flexibility of corrective responses are less efficient in older adults.