How the vestibular system turns sensing into action — the vestibulo-ocular reflex for stable gaze, the vestibulospinal reflexes for posture, and the cerebellar adaptation that keeps them calibrated.
The vestibulo-ocular reflex
The vestibulo-ocular reflex, or VOR, keeps vision steady when the head moves. As the head turns one way, the reflex rotates the eyes an equal amount the other way, so the image stays fixed on the retina.11
Head still — the reflex arc is at rest.
restafferentinterneuronmotorgaze held
The vestibulo-ocular reflex three-neuron arc — step the signal from the canal through the vestibular nucleus and motor neuron to the eye.
The VOR in three dimensions
The head can rotate about any axis, so the VOR must work in three dimensions. It does this by drawing on the three semicircular canals, each sensing rotation in its own plane.10
The vestibulospinal reflexes
While the VOR stabilises the eyes, the vestibulospinal reflexes stabilise the body. They adjust muscle tone to keep posture upright as the head and trunk move.25
Adaptation and suppression
The vestibular reflexes are not fixed. The brain continuously re-tunes them, so they stay accurate as the body grows, ages, or is injured.50