Visual categorical perception by rats with temporal, striate, or sham ablations

Rats were trained to discriminate a 0 degrees stripe from a 90 degrees stri pe in a two choice water maze. They were prepared with either Te2/3, partia l striate (PS), or sham lesions and retrained on the preoperative discrimin ation. In two separate experiments, excellent savings was observed for all groups. Next, trials were administered with novel stripe orientations defin ed as either between- or within-category problems. Performance accuracy ero ded rapidly for all groups in the first experiment, and no between-group di fferences were observed. In the second experiment, each session with catego rical stimuli was preceded by four reminder trials with the original stimul i. This improved accuracy for all groups, but it was found that animals wit h PS lesions, not animals with T2/3 lesions, were impaired on between-categ ory judgements. The impairment was not secondary to a disruption of basic v isual sensory processing or significantly larger lesions relative to the Te 2/3 group. As is the case for monkeys, accuracy with within-category stimul i was inferior to between-category stimuli for all groups. Possible reasons for this inter-species difference are discussed. (C) 2001 Lippincott Willi ams & Wilkins.