Observing the self and other in motion modulates the excitability of vestibulocollic reflexes

Vestibular inputs from the inner ear are at the basis of the vestibulo-spinal and vestibulocollic reflexes involved in balance control. Studies have focused on how attentional load and emotions influence balance, but low-level social cues, such as observing human bodies in motion, have been neglected. Yet, individuals observing another person in a challenging posture or in motion can experience imbalance, indicating that sensorimotor resonance between self and others is involved. The present study examines how the observation of videos depicting human bodies in motion modulates well-established neurophysiological signatures of vestibular information processing. The excitability of vestibulocollic reflexes was assessed by analyzing the waveform of vestibular-evoked myogenic potentials (VEMPs) over the sternocleidomastoid and trapezius muscles of 25 healthy participants (13 females, 12 males). Here we show that observing human bodies undergoing passive whole-body rotations reduced the VEMPs amplitude when compared to observing an object. Importantly, the modulation depended on the person depicted in the video as VEMPs were reduced when observing oneself, compared to someone else being moved. Direction-specific effects and electromyography recordings ruled out non-specific emotional and attentional effects. These results show that the vestibular system is sensitive to observing human bodies in motion, establishing new connections between social neuroscience and vestibular neurophysiology. Significance StatementVestibulocollic reflexes are thought to be consistent and of short latency. Yet, previous results show that observing conspecifics influences balance. We combined approaches from social neuroscience and vestibular electrophysiology to describe how the observation of self and other bodies in motion influences vestibular information processing. The results show that observing human bodies in motion reduces the amplitude of vestibulocollic reflexes involved in the stabilization of the head and balance. These results establish new relations between the sense of balance and social cognition and challenge classical views in vestibular neuroscience.