Color reversal-learning deficits after tectofugal pathway lesions in the pigeon telencephalon.

Pigeons were post-operatively trained to discriminate two colors presented simultaneously. After reaching criterion on this task, they were required to perform a series of reversals of the color discrimination in which the positive and negative consequences of the stimuli were interchanged. Lesions of ectostriatum (the telencephalic target of the avian tectofugal visual pathway) impaired the ability of pigeons to learn a color-reversal task. An examination of the pattern of sparing and loss of performance on this task after lesions of various components of the ascending visual pathways suggests that deficits in color-reversal learning observed after lesions of the visual Wulst are not due to the Wulst's connections with the thalamofugal pathway. Instead, the data suggest that the visual Wulst maintains a role in color-reversal learning through its connections with the tectofugal pathway.