Delayed Response Test Research Articles

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.

EFFECTS OF SUBTOTAL LESIONS OF FRONTAL GRANULAR CORTEX ON DELAYED REACTION IN MONKEYS

MANY STUDIES have shown that bilateral ablation of the frontal granular cortex in monkeys is followed by inability to perform at better than a chance level on the delayed-response test, even at delays of less than five seconds. Evidence for more precise localization of lesions within the prefrontal region which produce this symptom, however, is scant, elusive, and contradictory. In 1935 Jacobsen 1 found that after complete bilateral removal of all prefrontal cortex in the monkey except for a strip several millimeters in width anterior to the premotor area on one side only, the resulting deficit was quantitatively incomplete and was expressed as a shortening of the length of delay after which the animal could respond accurately. From this experiment, he suggested that the degree of deficit is inversely related to the amount of intact tissue of the frontal lobes. A similar experiment on a baboon, in which there was

Some physical and pharmacological factors affecting delayed response performance of baboons following frontal lobotomy.

HUNTER (13) devised the delayed response test as a method to evaluate, in animals, the variables intervening between the exposure of the subject to a stimulus configuration and that response of the subject which alters the stimulus configuration. Essentially, the method interposes a time interval between exposure and opportunity for such response. The investigations of Jacobsen and co-workers (15) demonstrated that the ability to perform adequately on delayed response can be used as an index of frontal lobe function in monkeys. These studies were interpreted as indicating that the frontal' cortex is essential to bridging the temporal gap interposed in the test situation. On the other hand, Nissen (29) and his co-workers interpreted their studies to indicate that delayed response performance is difficult for operated animals because of some failure which occurred at the time of stimulus presentation. Support of this viewpoint comes from Lashley (23) who, in describing the conditional reaction, pointed out that performance of this test depends on the animal's ability to take cognizance of the context in which the discriminanda appear. The failure of animals with frontal lesions to perform this test (34) adds credence to the view that such lesions limit an animal's ability to perform any test whenever performance depends on the animal's reaction t to an element in the stimulus configuration which is. not immediately altered by this reaction. Malmo (28) tested these alternative suggestions as to the temporal locus of the failure, and, using the indirect technique, demonstrated that if distractions are kept at a minimum during the test procedure, performance of the delayed response test is possible for frontal lobectomized animals. When distractions were interposed during the delay period the animals failed. These experiments again shifted attention to the delay period as the critical one for interpretation of frontal lobe function. Wade (32) sought to reduce distractibility by pharmacological means. She used barbiturates to

A study of factors influencing performance of dogs on a delayed response test.

A study of factors influencing performance of dogs on a delayed response test.