# Locomotion engages context-dependent motor strategies for head stabilization in primates

## TL;DR

This study shows that primates adjust their head stabilization strategies based on the context, such as walking on a treadmill versus overground, revealing flexible motor control.

## Contribution

The study reveals that head stabilization in primates uses context-dependent motor strategies, showing both conserved and reorganized muscle activity patterns.

## Key findings

- Treadmill walking shows a stable muscle activation structure that scales with speed.
- Overground walking leads to heightened muscle engagement and reorganized motor strategies.
- Elevated arousal preserves muscle recruitment structure but increases strength.

## Abstract

Flexible motor control is essential for navigating complex, unpredictable environments. Although movement execution is often associated with stereotyped patterns of neural and muscular activation, the degree to which these patterns are conserved versus flexibly reorganized to meet task demands across diverse contextual changes has not been well characterized. Here we recorded head and body kinematics alongside muscle activity in rhesus monkeys during head stabilization—crucial for maintaining gaze and balance—while walking on a treadmill at various speeds, and during overground locomotion in the presence or absence of enhanced autonomic arousal. Dimensionality reduction analyses revealed a flexible control strategy during treadmill walking: a stable activation structure that scaled with speed. In contrast, overground walking evoked heightened muscle engagement and more substantial changes in organization. This pattern largely persisted even during elevated arousal, with larger pupil size linked to stronger but structurally preserved muscle recruitment. Together these findings demonstrate that the brain dynamically adapts motor coordination to context even for automatic behaviors, underscoring the need to examine control strategies in a wide range of conditions.

Head stabilization arises from population geometry of neck muscle activity that is conserved and smoothly scaled across walking speeds, but reorganized during more natural overground locomotion, revealing flexible, context-dependent motor control.