| Abstract: | Eight homing pigeons were trained preoperatively on a mixed delayed matching-to-sample (DMTS) task in which 6 different conditions were presented randomly: simultaneous matching and 0-, 1-, 2-, 4-, and 8-sec delays. Ss that sustained extensive or complete damage to the visual Wulst, a multilaminate region in the pigeon telencephalon which occupies the dorsal aspect of the cerebral hemisphere, and moderate damage to the hyperstriatum ventrale showed a decrease in accuracy of performance to chance levels in all of the delay conditions as well as in simultaneous matching. After extensive retraining on the 0-sec-delay matching alone, performance on 0-sec-delay and simultaneous matching, presented in mixed DMTS, improved to between 70 and 90% correct. However, performance on delay conditions remained at chance level. All but 1 S failed to show signs of postoperative improvement on delay problems in the course of the final testing. Data suggest that the conditional property of the task was a critical factor in the initial drop in accuracy on all of the presented problems. The relatively permanent loss of accuracy on all delay conditions is attributed mainly to the temporal separation of sample and comparison stimuli. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) |
