Function of association cortex in monkeys

Four normal monkeys and six with extensive unilateral decortication plus destruction of the contralateral frontal and posterior association areas were studied in a series of twelve experiments. As compared with the normal controls, the operated animals were (a) neither seriously nor permanently impaired in their performance on visual search or patterned string problems, (b) slightly, but to a significant degree, retarded on discrimination reversal, (c) not permanently deficient in the discrimination of tridimensional objects, (d) significantly inferior in discriminating bidimensional patterns, particularly those which did not differ in colour, (e) impaired on delayed response tests in which the delay intervals were varied randomly, and (f) markedly and consistently inferior on two- and three-choice oddity problems. Performance on the double alternation problem did not differentiate the normal and operate groups.

It was pointed out that all the operated monkeys were deficient in their ability to reverse response tendencies to previously rewarded stimuli. The restricted applicability of the concepts of localization, mass action, and equipotentiality is discussed in terms of the results of this study.