The vestibular organs sense head motion: semicircular canals sense rotation; otoliths sense linear acceleration (including gravity). The central vestibular system distributes this signal to the oculomotor, head movement, and postural systems for gaze, head, and limb stabilization1.
The visual (optokinetic) and somato-sensory inputs also provide signals for balance, in a partially redundant but complementary manner to those from the labyrinth.
These different sensory inputs are used by the vestibular system both for normal behaviour and as a substrate for recovery in response to vestibular disease.
The visual system complements the vestibular system: for the VOR, visual (optokinetic) signals are used instead of labyrinthine signals for the low-frequency, sustained components of head rotation. Somatosensory and visual signals help stabilise posture in a similar manner. The critical importance of the interactions between these different sensory signals is reflected in the fact that they converge on the same neurons within the vestibular nuclei. One can easily envisage how disturbance of any of the sensory inputs to the vestibular nuclei might lead to a sensory conflict and abnormal vestibular sensation2.
