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Adult rats were trained on a white versus black card discrimination in a circular water tank. Three independent variables were manipulated: lesion (sham, lateral occipital, medial occipital), dose of ORG 2766 administered (0 or 25 micrograms in saline on alternate days for 18 days), and time of administration (during the post-surgical recovery interval or during post-operative testing). Both visual cortical lesions produced a prominent retention deficit and defective pattern vision. Neither post-surgical nor concurrent administration of ORG 2766 improved visual functions. These results, along with a growing body of evidence, challenge the generality of the positive influences of ORG 2766 upon behavioral recovery observed in animals with limbic lesions.

Rats were trained to discriminate a 0 degrees stripe from a 90 degrees stripe in a two choice water maze. They were prepared with either Te2/3, partial striate (PS), or sham lesions and retrained on the preoperative discrimination. In two separate experiments, excellent savings was observed for all groups. Next, trials were administered with novel stripe orientations defined as either between- or within-category problems. Performance accuracy eroded rapidly for all groups in the first experiment, and no between-group differences were observed. In the second experiment, each session with categorical stimuli was preceded by four reminder trials with the original stimuli. This improved accuracy for all groups, but it was found that animals with PS lesions, not animals with T2/3 lesions, were impaired on between-category judgements. The impairment was not secondary to a disruption of basic visual sensory processing or significantly larger lesions relative to the Te2/3 group. As is the case for monkeys, accuracy with within-category stimuli was inferior to between-category stimuli for all groups. Possible reasons for this inter-species difference are discussed.