Effects of Wulst and ectostriatum lesions on repeated acquisition of spatial discrimination in pigeons.

The avian telencephalon has two visual areas, (1) a 'Wulst' that consists of hyperstriatum accessorium, hyperstriatum intercalatus superior and hyperstriatum dorsale, and (2) the ectostriatum. Deficits in visual discrimination have been observed after ectostratal lesions but not after Wulst lesions. In the present experiments, the cognitive functions of the Wulst in pigeons were examined. Pigeons were trained on repeated acquisition of a three key discrimination. Every time the subjects reached the criterion of discrimination, they were trained on different discriminations in which one of two previously incorrect keys became the correct key. The Wulst lesions disrupted the acquisition of discrimination, while the ectostriatal lesions did not.