Cerebellar and cerebral inputs to cortico-cortical and corticofugal neurons
in areas 5 and 7 in the cat.
Kakei, S., J. Yagi, T. Wannier, J. Na, and Y. Shinoda.
Department of Physiology, School of Medicine, Tokyo Medical and Dental
University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113, Japan; Department of
Physiology, School of Medicine, Kyorin University, Mitaka, Tokyo, 181, Japan;
and Department of Physiology, University Bern, B[umlaut]uhlplatz 5, CH-3012,
Bern, Switzerland.
APStracts 2:0066N, 1995.
SUMMARY AND CONCLUSIONS
1. In the parietal cortex (Px, areas 5 and 7), the organization and
characteristics of cerebellar and cerebral inputs and their effects on
efferent neurons were investigated using intracellular and extracellular
recording techniques in the anesthetized cat. 2. Evoked field potential
analysis revealed that two regions of the Px, the caudal bank of the ansate
sulcus (Ans. S.) and the crown of the suprasylvian gyrus (Ssyl. G.), received
converging input from the dentate and the interpositus nucleus. The cerebellar
input to the caudal bank of the Ans. S. was relayed via the ventrolateral
region of the ventroanterior-ventrolateral (VA-VL) complex of the thalamus,
whereas the cerebellar input to the crown of the Ssyl.G. was relayed via the
dorsomedial region of the VA-VL complex. 3. A total of 176 neurons were
recorded intracellularly in the Px to examine inputs from the cerebellum. Of
these, 72 neurons were cortico-cortical neurons projecting to the Mx, and 48
were corticofugal neurons to the pontine nucleus (PN). Intracellular staining
with horseradish peroxidase revealed that the former cortico-cortical neurons
were layer III pyramidal neurons and the latter corticofugal neurons were
layer V pyramidal neurons. 4. Stimulation of the brachium conjunctivum (BC)
produced di- or polysynaptic EPSPs in cortico-cortical neurons projecting to
the motor cortex (Mx) and corticofugal neurons to the pontine nucleus in the
Px. The characteristics of BC-evoked EPSPs were different between the bank of
the Ans. S. and the crown of the Ssyl. G. In the bank of the Ans. S., the
slope of the rising phase of the BC-evoked EPSPs was steeper, and their
minimum latency was shorter by 0.8 ms than those in the crown of the Ssyl. G.
These differences may reflect differences in the terminal distribution and
conduction velocity of the thalamocortical fibers relaying cerebellar input to
these two parietal areas. 5. Stimulation of the Mx produced mono- or
disynaptic EPSPs in both cortico-cortical neurons projecting to the Mx and
corticofugal neurons projecting to the pontine nucleus in the Px. For each
neuron, effective sites for inducing EPSPs were distributed very widely and
sometimes covered both areas 4 and 6. Extensive cortico-cortical projection
from the Mx to the Px was confirmed by injection of an anterograde tracer into
the Mx. 6. These data indicate that neurons in the Px receive inputs from both
the cerebellum and the Mx, and send outputs to the Mx and the cerebellum. This
input-output organization puts the Px in a good position to integrate
feedforward motor output signals from the Mx and the cerebellum and feedback
sensory information from the periphery for adequate voluntary movement.
Received 7 September 1994; accepted in final form 15 February 1995.
APS Manuscript Number J564-4.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 3 April 1995.