Cortical localization of symbolic processes in the rat: III. Impairment of anticipatory functions in prefrontal lobectomy in rats.

Abstract

Rats, when they have first learned a maze, run more and more rapidly as they approach the goal; this is called a "goal gradient." After additional training, however, they begin to slow down just before they reach the goal, an "anticipatory gradient." The hypothesis for expt. was that the anticipatory gradient involves symbolic process of "imagery" and "expectancy" of the goal that are dependent upon the prefrontal cortical areas of the rat, whereas the goal gradient does not. One group of rats was subjected to prefrontal lobectomy and trained on a maze; another group of 8 unoperated rats served as control. Time on each of 3 segments of the maze was recorded; after preliminary training, 5 trials a day for 13 days were run. The normal group showed both the goal and anticipatory gradients as expected of normal animals; the operated group, although they displayed a marked goal gradient in their running, gave no evidence of anticipatory gradient. Thus it can be concluded that anticipatory factors in maze running require the prefrontal areas. This suggests more localization of function in the rat''s cortex than previous studies have shown. The possibility of using cortical lesions for the separation of psychological functions was strikingly illustrated by these results.