The interstitial nucleus of Cajal is a collection of neurons in the mesencephalon (midbrain) which are involved in integrating eye position-velocity information in order to coordinate head-eye movements - especially those related to vertical and torsional conjugate eye movements (gaze). It also mediates vertical gaze holding.

Bilateral projections to the oculomotor (cranial nerve III) and trochlear (cranial nerve IV) nuclei represent its principal outputs. It forms reciprocal connections with vestibular nuclei. It also has additional afferents and efferents. Some of the nucleus' connections pass through the medial longitudinal fasciculus, and the posterior commissure.

It is one of the accessory oculomotor nuclei.

The interstitial nucleus of Cajal is a diffuse collection of mid-sized, parvalbumin-containing premotor neurons of the midbrain reticular formation.

The nucleus forms reciprocal connections with the vestibular nuclei (through the MLF). It forms connections with the ipsilateral rostral interstitial nucleus of medial longitudinal fasciculus. Some of its contralateral connections cross over the posterior commissure.

It receives afferents (in fact, forms reciprocal connections) with the vestibular nuclei (via the MLF), and the nucleus prepositus hypoglossi.

It receives afferents from the spinal cord through the spinomesencephalic tract.

It receives afferents from the visual association areas via the corticotectal tract.