General variability leads to specific adaptation toward optimal movement policies

Area of Science:

• Neuroscience
• Biomechanics
• Robotics

Background:

• The human nervous system adapts motor control policies for optimal movement in changing contexts.
• Adaptation strategies, particularly how the nervous system explores variations to find optimal policies, remain unclear.

Purpose of the Study:

• To investigate how human participants explore variations in their motor control policy to identify optimal policies in new walking contexts.
• To analyze the adaptation of step frequency, ankle angle range, and soleus/medial gastrocnemius muscle activity.

Main Methods:

• Participants walked using exoskeletons applying assistive ankle torques, creating novel movement contexts.
• Analysis focused on changes in step frequency, ankle angle range, and muscle activity (soleus, medial gastrocnemius) over time.

Main Results:

• Movement variability increased initially in new contexts and decreased with experience across all analyzed variables.
• Adaptive changes in variable magnitudes correlated with reduced energetic cost.
• Adaptation and variability reduction occurred at different timescales for different variables, suggesting a refined optimization process.

Conclusions:

• Exploration through general motor variability facilitates specific adaptation towards optimal movement policies.
• The nervous system systematically reduces its search space to optimize movement in new environments.