Recovery of function after brain damage: The motivational specificity of spared neural traces

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

“…Subsequently, the animals were subjected to visual decortication and, after a 2-week rest, returned to the apparatus and trained on the same brightness discrimination but now to avoid foot-leVERE shock. Previous results using this procedure (LeVere & Davis, 1977) demonstrated that, while the memory engrams of the preoperatively learned brightness discrimination for water reinforcement were spared, they did not influence the postoperative performance of a brightness discrimination learned to avoid footshock. On the basis of this result, one of two predictions would be made depending upon how 8-azaguanine facilitated recovery of function in the previous experiment.…”

“…In this experiment, all training was subsequent to visual decortication, and the question of utilization was evaluated by training rats on two similar brightness discriminations but under different motivations. We chose to change motivational state to test utilization because our previous research (LeVere & Davis, 1977) demonstrated that changing motivation between preoperative learning and postoperative recovery would eliminate the reversal impairment described by LeVere andMorlock (1973, 1974). However, the results of the present experiment clearly showed that the destriate rat is as adept as its normal counterpart at utilizing what is learned in one discrimination during training in another discrimination.…”

“…Thus, the initial preoperative errors, the original preoperative learning, the postoperative behavioral deficit, and the subsequent recovery of function are all postulated to represent a similar learning process. The problem is, however, that more recent data suggest that the postoperative behavioral deficit does not represent a loss of memory, a loss of the motivation to perform the preoperatively learned behavior, or a loss of the ability to utilize previously learned behaviors (LeVere & Davis, 1977;LeVere et aI., 1979;LeVere & Morlock, 1973, 1974. Also, the effect of amphetamine (Braun, Meyer, & Meyer, 1966;Ritchie, Meyer, & Meyer, 1976) and the effect of the RNA antimetabolite 8-azaguanine (Davis & both demonstrate that whatever the recovery process is, it is not a rerun of preoperative acquisition.…”

“…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

“…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.…”