Synergies Stabilizing Vertical Posture in Spaces of Control Variables

Area of Science:

• Neuroscience
• Biomechanics
• Motor Control

Background:

• Maintaining vertical posture involves complex neural processing.
• The central nervous system (CNS) must effectively manage numerous neural commands to ensure stability.
• Understanding the CNS's strategies for postural stabilization is crucial for addressing movement disorders.

Purpose of the Study:

• To investigate whether the CNS employs coordinated neural commands to stabilize vertical posture.
• To explore the relationship between referent coordinates (RC) and muscle co-activation in postural control.
• To determine if synergistic control strategies exist within the neural command space for posture stabilization.

Main Methods:

• Participants stood under external load and experienced unloading episodes.
• Linear and hyperbolic regressions analyzed the relationship between force, center of mass, RC, and apparent stiffness (k).
• Randomization analysis and motor equivalent deviation analysis assessed neural control variable co-variation.

Main Results:

• High co-variation between RC and apparent stiffness (k) was observed, stabilizing horizontal force.
• Increased co-variation correlated with lower apparent stiffness, suggesting co-activation can be destabilizing.
• Motor equivalent deviations were significantly larger than non-motor equivalent ones, indicating specific control synergies.

Conclusions:

• This study provides the first evidence of posture-stabilizing synergies within neural control variables.
• The findings demonstrate the CNS's sophisticated strategies for managing redundant neural commands to maintain balance.
• These discoveries have significant implications for understanding and treating postural disorders and for developing rehabilitation interventions.