Anatomy and physiology of the primate interstitial nucleus of Cajal I. efferent projections

Abstract

1. The efferent projections of the interstitial nucleus of Cajal (NIC) were studied in the squirrel monkey after iontophoretic injections of biocytin and Phaseolus Vulgaris leucoagglutinin into the NIC. To ensure the proper placement of the tracer, the same pipettes were used to extracellularly record the discharge pattern of NIC neurons. 2. Three projection systems of the NIC were distinguished: commissural (through the posterior commissure), descending, and ascending. 3. The posterior commissure system gave rise to dense terminal fields in the contralateral NIC, the oculomotor nucleus, and the trochlear nucleus. 4. The descending system of NIC projections deployed dense terminal fields in the ipsilateral gigantocellular reticular formation and the paramedian reticular formation of the pons, as well as in the ventromedial and commissural nuclei of the first two spinal cervical segments. It also gave rise to moderate or weak terminal fields in the vestibular complex, the nucleus prepositus hypoglossi, the inferior olive, and the magnocellular reticular formation, as well as cell groups scattered along the paramedian tracts in the pons and the pontine and medullary raphe. 5. The ascending system of NIC projections gave rise to dense terminal fields in the ipsilateral mesencephalic reticular formation and the zona incerta as well as moderate or weak terminal fields in the ipsilateral centromedian and parafascicular thalamic nuclei. It also provided dense bilateral labeling of the rostral interstitial nucleus of the medial longitudinal fasciculus and the fields of Forel, and moderate or weak bilateral labeling of the mediodorsal, central medial, and central lateral nuclei of the thalamus. 6. Models of saccade generation that rely on feedback from the velocity-to-position integrators and include the superior colliculus in their local feedback loop are contradicted because no fibers originating from the NIC traveled to the superior colliculus to deploy terminal fields. 7. Consistent with its morphological and functional diversity, these data indicate that the primate NIC sends signals to a multitude of targets implicated in the control of eye and head movements.

Synaptic Control of Motoneuronal Excitability

“…The oculomotor nucleus and the trochlear nucleus receive afferents from the rostral interstitial nucleus of the medial longitudinal fasciculus (GABAergic and glutamatergic; Refs. 1180,1335) and interstitial nucleus of Cajal (654). A small number of neurons in the locus coeruleus, trigeminal sensory complex and olivary pretectal nucleus project to the oculomotor nucleus (191,455,646).…”

Three-Dimensional Eye–Head Coordination After Injection of Muscimol Into the Interstitial Nucleus of Cajal (INC)

“…Moreover, the INC could possibly be part of a distributed circuit, including the vestibular nuclei and the nucleus prepositus hypoglossi (Blazquez et al 2006;Kokkoroyannis et al 1996;Moschovakis 1997), that implements the neural integration process.…”

Immunoreactivity for calcium-binding proteins defines subregions of the vestibular nuclear complex of the cat

“…Work in the rodent suggests that the cerebellum and the eighth nerve are in fact the only sources of calbindin-immunoreactive fibers in the VNC (Kevetter and Leonard 1997;Bäurle et al 1998). The possible sources of parvalbuminimmunoreactive fibers are more numerous, as several brainstem structures with parvalbuminimmunoreactive cells, including the interstitial nucleus of Cajal (Kokkoroyannis et al 1996;Horn et al 1999), the rostral interstitial nucleus of the MLF (Horn and Büttner-Ennever 1998) and inhibitory and excitatory burst neurons of the reticular formation (Horn et al 1995) may contribute the parvalbumin-immunoreactive fibers that are seen in the MLF and VNC.…”