The effects of wulst lesions on simple visual discrimination performance in the pigeon

Pigeons with lesions involving the hyperstriatum accessorium, hyperstriatum intercalatus superior and hyperstriatum dorsale were compared with sham operated controls on acquisition of a simple colour/brightness discrimination. Correct and incorrect choices together with choice latencies were recorded. The lesioned birds' performance on the discrimination aspects of the task was not inferior to controls. However, the choice times of the lesioned group were significantly longer than controls. The within session pattern of choice latencies was also significantly different, with the lesioned birds beginning each session with longer latencies than controls but ending the session with choice latencies equivalent to controls. The lesion effect is attributed to damage to a mechanism concerned with arousal or response facilitation within the anterior Wulst.