Axis-specific neuro-musculoskeletal contributions to postural stability and vibration avoidance in mice

In modern industrial societies, animals including humans are frequently exposed to external mechanical oscillations such as whole-body (WB) vibration. To ensure postural stability and effective movement, animals must appropriately regulate their responses to such vibratory disturbances. Therefore, understanding how animals respond to vibration is of growing importance. However, compared with humans, knowledge of mouse responses to WB vibration remains limited, as previous studies have primarily examined anesthetized or euthanized mice. Here, we used high-speed video-based quantitative analyses to characterize body part movements in both awake and anesthetized mice under vertical, longitudinal, and lateral WB vibration. Awake mice exhibited lower resonance frequencies and smaller displacement amplitudes than anesthetized mice during both vertical and lateral WB vibration, whereas longitudinal WB vibration produced minimal differences. These results indicate that the active neuro-musculoskeletal (NMS) system contributes to postural stability in a vibration axis-dependent manner. Axis-specific vibration control may reflect an evolutionarily acquired balance between postural stability and locomotor efficiency. Vibration modeling further suggests that the NMS system acts as a vibration absorber by reducing stiffness and providing feedback-controlled active damping, analogous to active vehicle suspensions. Behavioral preference tests revealed that mice selectively avoid vertical WB vibration at specific frequencies, but not lateral or longitudinal vibration, regardless of resonance frequencies. These findings suggest that resonated body part displacement during WB vibration do not directly determine vibration discomfort, and that vertical WB vibration along the gravitational axis exerts a distinct impact on postural control and behavior in mice. This study provides new insights into the biomechanics and behavior of quadrupeds exposed to WB vibration, with analogies to four-wheeled vehicles offering a useful perspective.