Vestibular Nuclei Projections

The vestibular nuclei send neuronal projections to the following targets above and below the brainstem:

1. Projections to the cortex occur via the thalamus, as with other sensory pathways, although there is no equivalent “vestibular cortex” to the auditory and visual areas.

2. There is a rich supply of second-order vestibular neurons to the cerebellum to coordinate movements.

3. Vestibular input to motor neurons of the lower limb occurs via the vestibulospinal tract, which assists in the automatic maintenance of balance.

4. Vestibular input to motor neurons of the neck facilitates independent maintenance of head position.

5. Projections to the motor neurons for extraocular muscles keep the eyes focused on an object as the body moves.

   • The vestibuloocular reflex causes the eyes to turn in the direction opposite that of the rotation of the head.

   • For example, if the gaze is fixed on a particular object, turning to the right causes both eyes to move toward the left, thereby keeping the object in view.

   • The vestibuloocular reflex relies on projections from the vestibular nucleus to nuclei of CN III, IV, and VI, which control eye movements.