TOPOGRAPHY AND RECIPROCAL ACTIVITY OF CEREBELLAR PURKINJE CELLS
IN THE UVULA-NODULUS MODULATED BY VESTIBULAR STIMULATION.
H. Fushiki and N.H. Barmack.
R.S. Dow Neurological Sciences Institute, Legacy Good Samaritan Hospital &
Medical Center, Portland, Oregon, USA, and Department of Otolaryngology Toyama
Medical & Pharmaceutical University, Toyama, JAPAN.
APStracts 4:198N, 1997.
ABSTRACT
In the rabbit uvula-nodulus, vestibular and optokinetic information is mapped
onto parasagittal zones by climbing fibers. These zones are related
functionally to different pairs of vertical semicircular canals, otolithic
inputs and horizontal optokinetic inputs. Vestibular stimulation restricted to
one of these zones modulates climbing fiber responses (CFRs). Within each of
these zones, simple spikes (SSs) are modulated reciprocally with CFRs. In
rabbits anesthetized with chloralose-urethane, we have used vestibular and
optokinetic stimulation to evoke CFRs within a parasagittal zone, while
recording from Purkinje cells in adjacent zones. We have examined whether the
climbing fiber responses evoked by vestibular stimulation in one zone
influence the simple spikes of an adjacent zone. CFRs and SSs were recorded
during roll vestibular stimulation. The orientation of the head of the rabbit
with respect to the axis of rotation was varied systematically so that a
climbing fiber null plane could be determined. This null plane was the
orientation of the head about the vertical axis at which no modulation of the
CFR was observed during rotation about the longitudinal axis of the vestibular
rate table. In the left uvula-nodulus, a medial sagittal stripetending through
all the folia contained Purkinje cells with CFRs that had optimal planes of
stimulation co-planar with the left posterior-right anterior semicircular
canals (LPC - RAC). Lateral to this strip was a strip of Purkinje cells with
CFRs that were characterized by optimal planes corresponding to stimulation of
the left anterior-right posterior semicircular canals (LAC - RPC). SSs in
Purkinje cells were modulated out of phase with CFRs from the same Purkinje
cell. The depth of modulation of both CFRs and SSs was reduced during rotation
in the climbing fiber "null plane." The depth of modulation of SSs was
greatest when recorded from Purkinje cells located at the center of
semicircular canal-related strip. We observed that: 1) All folia of the uvula-
nodulus receive vestibular climbing fiber inputs, 2) These climbing fiber
inputs convey information from the vertical semicircular canals and otoliths,
but not the horizontal semicircular canals, 3) CFRs evoked in a particular
sagittal zone do not influence SSs in adjacent zones, and 4) Modulation of a
CFRs in a particular Purkinje cell can occur without modulation of SSs in the
same Purkinje cell, although modulation of SSs was not observed in the absence
of CFR modulation. 5) Modulation of SSs sometimes preceded that of CFRs in the
same cell, implying that interneuronal pathways may contribute to SS
modulation. Climbing fiber-driven Golgi cells whose inhibitory axon terminals
end on granule cell dendrites in the classic glomerular synapse, may provide
this interneuronal mechanism.
Received 11 March 1997; accepted in final form 15 August 1997.
APS Manuscript Number J209-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 28 August 1997