ANALYSIS OF CHANGES IN INDIRECT DELAYED RESPONSE PERFOMANCE IN MONKEYS WITH PREFRONTAL LESIONS

7 squirrel monkeys with damage to the dorsolateral prefrontal cortex were comparable to 7 normal controls in their performance on a brightness discrimination task. Normal and prefrontal performance was also comparable under a 0-sec indirect delayed response (DR) procedure involving 2 variations of the stimulus cues used in the original discrimination task. Furthermore, when tested on the same DR task with a 2-sec delay, 1 group of prefrontal Ss was deficient with respect to normal S under 1 of the stimulus-cue situations, but showed no deficit on the 2nd stimulus-cue situation. A 2nd group of prefrontal Ss which received the same 2 stimulus-cue situations in reverse order, were comparable to normal controls throughout 2-sec DR testing. It is hypothesized that dorsolateral prefrontal damage in the squirrel monkey results in an increased dependence upon external cues for the guidance of behavior when modification of response patterns is required. (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1969 American Psychological Association.