VESTIBULAR INTEGRATORS IN THE OCULOMOTOR SYSTEM

The interstitial nucleus of Cajal (INC) and the nucleus prepositus hyp oglossi (nph) are key elements in the vertical and horizontal oculomot or neural integrators, respectively. In this article, we attempt to de velop possible circuits for these vestibular integrators by synthesizi ng recent information on the properties and connections of neurons inv olved in the integration process. We also examine how the cerebellar f locculus could play a role in the vertical integrator and vestibule-oc ular reflex (VOR) as well as in the modulation and plasticity of the V OR. We suggest that the circuitry for the vertical integrator involves the cerebellar flocculus in addition to the already proposed circuits distributed between the INC and the vestibular nuclei. The horizontal vestibular integrator is also distributed and seems to be characteriz ed by functional compartmentalization. Both integrators play a wider r ole than simply transforming velocity-coded signals into position comm ands and may be pivotal in the short- and long-term modulation of the various oculomotor subsystems.