Nature of visual recovery following posterior neodecortication in the hooded rat.

Abstract

Subsequent to bilateral, single-stage posterior neodecortication, rats were either retrained on a preoperatively learned brightness discrimination or trained on the reversal of the preoperatively learned discrimination. Postoperative relearning was significantly retarded when the discrimination involved a reversal of the original brightness discrimination. These results then suggest that the preoperatively established brightness habit is not exclusively localized in the neocortex and that postoperative recovery of the discrimination does not involve relearning a new and independent memory engram.

Recovery of function after brain damage: A theory of the behavioral deficit

“…If certain animals (e.g., rats) are trained on a twochoice brightness discrimination and then subjected to visual neodecortication, the preoperatively acquired behavior is completely disrupted (Horel, Bettinger, Royce, & Meyer, 1966;Lashley, 1935;LeVere & Davis, 1977;LeVere & Morlock, 1973, 1974. However, if the lesioned animals are given postoperative retraining on the discrimination, then the brightness habit may be reinstated and in approximately the same number of training trials required to initially learn the behavior.…”

Recovery of function after brain damage: Support for the compensation theory of the behavioral deficit

“…For example, the rat's "loss" of a preoperatively learned brightness habit following visual decortication (Lashley, 1935) now can be shown, with appropriate tests, to be spared (Braun et al, 1967;LeVere & Morlock, 1973). The point is that there may be many reasons why a braininjured subject is unable to perform some particular behavior after brain injury, and an induced behavioral loss is but one of these reasons.…”

“…Compensation thus appears to be a dominant influence when visual decorticate rats attempt new learning. Our final question, then, was whether this compensatory consequence of brain injury also would hold when the rat attempted to recover a preoperatively established behavior that, while disrupted by visual decortication, could nonetheless be demonstrated to have been spared LeVere & Davis, 1977;LeVere et al, 1979;LeVere & Morlock, 1973, 1974.…”

“…The apparatus was a modified version of our Yerkes two-choice brightness discrimination box (see LeVere & Morlock, 1973). It consisted of a start compartment separated from a choice compartment by a guillotine door.…”

“…To accomplish this we used the shock-motivated · two-choice brightness discrimination procedure that we previously had used to evaluate recovery of function following visual decortication in rats (see LeVere & Morlock, 1973). However, during postoperative recovery training in the present experiments, the brightness cues were compounded with supplemental nonvisual discriminative cues.…”