Behavioral effects of cerebral injury in relation to changes in motivation

24 female rats were trained to jump at the sound of a buzzer in order to escape shock. The intensity of the current was 250 |ma. Retention tests were given after a rest period of 4 days. Then the animals were subjected to bilateral lesions in the critical auditory area. After a recovery period of 4 days they were tested for retention. 8 animals were tested with the original intensity of current, 8 with an intensity 50 |ma. lower, and the remaining 8 with an intensity 50 |ma. higher. There were no significant differences in the postoperative scores of the 3 groups. When the animals were grouped on the basis of extent of lesion, however, it appeared that savings scores are highest with the greatest intensity of shock. There is thus some evidence, although the differences are not statistically reliable, that an increase in the intensity of electrical stimulation compensates for the effects of cortical injury.