Journal of Neurophysiology, Vol 43, Issue 3 792-806, Copyright © 1980 by APS
Spatial localization in cats reared with strabismus
C. R. Olson
1. The capacity for judging the location of an object relative to the body
(egocentric localization) was assessed in cats by measuring the landing
position attained when the cat jumped toward a platform viewed from a known
distance. 2. Normal cats and kittens land at center of the platform when
using one eye or both. In contrast, nine animals tested immediately after
tenotomy of the medial rectus muscle of one eye all landed consistently
off-center when using the operated eye. The direction of the error was
predictable from the assumption that the cat was unaware of the eye's
deviation from its natural position. Thus, proprioceptive reafference is
not capable, under these conditions, of supporting an accurate awareness of
eye position. 3. After initial testing, all cats were maintained in a
normal environment with both eyes open and were tested intermittently.
Jumps guided by the deviated eye became accurate over a period of weeks in
kittens younger than 4 mo. In contrast, behavioral adjustment in older
kittens required many months. An adult cat displayed almost no adjustment
over a period of 9 mo. 4. Five additional kittens were first tested several
months after the onset of strabismus. These animals manifested accurate use
of the operated eye from the first trial onward. Therefore, acquisition of
accurate use of the deviated eye is not dependent on repeated testing. 5.
Two kittens subjected to early exodeviation of one eye displayed a reduced
capacity for adjustment when subjected to late exodeviation of the second
eye. Thus, changes in neural function resulting from early strabismus (for
instance, the loss of binocular connectivity in striate cortex) do not
produce persistent behavioral flexibility. 6. In two strabismic kittens
with a fully developed compensatory adjustment of monocular egocentric
localization, the capacity for judging the relative location of two objects
viewed simultaneously through separate eyes was assessed through use of a
two-choice visual discrimination paradigm. One animal made predictable
systematic errors, while the other exhibited correct judgments. Thus, it
appears that a compensatory shift of retinal correspondence may occur in
some strabismic kittens, but that such a change is not necessary for
accurate use of the deviated eye in monocular visual guidance. 7. A number
of observations are described that tend to indicate that cats reared with
strabismus continue to use both the deviated and the nondeviated eye for
visual guidance under binocular viewing conditions, unlike many human
strabismics.
