Differential effects of early and late lesions of frontal granular cortex in the monkey

Abstract

Summary Bilateral ablations of dorsolateral frontal granular cortex were performed in four monkeys prior to the 35th postnatal day and in three monkeys at 3 years of age. Subsequent testing procedures involved the learning of a color discrimination, a series of delayed response tests and a delayed alternation task. No differences were found between early- and late-frontals in learning the color problem. All animals were equally impaired in delayed alternation performance. Delayed response testing revealed a marked superiority for early-frontals, relative to the performances of later-frontals. Differential delayed response performances of the two frontal groups were not due to differences in either surface lesion or retrograde thalamic degeneration. It was concluded that either a compensatory neural reorganization or a progressive cerebral maturation might account for the sparing of delayed response capacity in the early frontal preparations.