VISUAL RESPONSE CHARACTERISTICS OF RETINAL SLIP NEURONS IN THE NUCLEUS OF
THE OPTIC TRACT AND DORSAL TERMINAL NUCLEUS OF THE ACCESSORY OPTIC SYSTEM IN
CATS WITH CONGENITAL STRABISMUS.
Distler, C. and K. P. Hoffmann.
Allgemeine Zoologie und Neurobiologie, Ruhr-Universit„t Bochum ND 7,
Postfach 102148, D-44780 Bochum, FRG, Tel. 0234/7004363, Fax:
0234/7094185.
APStracts 2:0306N, 1995.
SUMMARY AND CONCLUSIONS
1. Visual response properties of neurons in the nucleus of the optic tract
(NOT) and dorsal terminal nucleus of the accessory optic tract (DTN) were
electrophysiologically investigated in five congenitally strabismic cats and
compared to normal adult cats and 3-4 week old kittens. 2. As in normal cats,
NOT-DTN cells of strabismic cats preferred horizontal ipsiversive stimulus
movement. However, NOT-DTN neurons in strabismic cats altered their activity
to a lesser amount per degree change of stimulus direction than do normal
adult cats. In addition, NOT-DTN cells in strabismic cats exhibited a broader
directional tuning, i.e. they increase their activity to a broader range of
directions than control NOT-DTN cells. 3. Spontaneous activity and activity
difference between preferred and non-preferred direction were significantly
lower in NOT-DTN neurons of strabismic than in normal adult cats and resembled
that found in 3 week old kittens. Maximal stimulus related activity was lower
than in normal adult cats but higher than in kittens. 4. Visual latencies to
onset of movement in the preferred direction were indistinguishable in
strabismic and in normal adult cats. Visual latencies to onset of movement in
the non-preferred direction, however, were shorter in strabismic than in
normal adult cats. 5. The average velocity tuning curve of NOT-DTN cells in
strabismic cats was very flat without a well-defined optimal stimulus
velocity. Thus, it closely resembled data from 3 week old kittens. 6.
Binocular convergence was significantly altered to a stronger dominance of the
contralateral eye in NOT-DTN of strabismic cats. This reduction of binocular
neurons was less pronounced than in cats with artificially induced strabismus
or in 3 week old kittens. 7. In conclusion, the data presented here for
retinal slip neurons in the NOT-DTN of strabismic cats closely resemble those
from 3 week old kittens where no functional cortical input to the NOT-DTN is
present. However, the elevated stimulus driven activity and the still
relatively high degree of binocularity give a clear indication for a
functional albeit weak and abnormal cortical input to the NOT-DTN in these
naturally strabismic cats.
Received 1 May 1995; accepted in final form 18 October 1995.
APS Manuscript Number J292-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95