ANATOMY AND PHYSIOLOGY OF THE PRIMATE INTERSTITIAL NUCLEUS OF CAJAL. I.
EFFERENT PROJECTIONS.
KOKKOROYANNIS, T., C.A. SCUDDER, C.D. BALABAN, S.M. HIGHSTEIN AND A.K.
MOSCHOVAKIS.
Laboratory of Neurophysiology, Dept. of Basic Sciences, Faculty of
Medicine, University of Crete, Eye and Ear Institute, Pittsburgh University,
and Department of Otolaryngology, Washington University School of Medicine in
St. Louis®MDNM¯.
APStracts 2:0284N, 1995.
SUMMARY AND CONCLUSIONS
1) The efferent projections of the interstitial nucleus of Cajal (NIC) were
studied in the squirrel monkey following iontophoretic injections of biocytin
and PHA-L 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, 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, 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 labelling of the rostral interstitial nucleus of the
medial longitudinal fasciculus, and the Fields of Forel, and moderate or weak
bilateral labelling 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 since no fibers originating from
the NIC travelled 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.
Received 17 April 1995; accepted in final form 11 September 1995.
APS Manuscript Number J255-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 31 October 95