Lateral hyperstriatal lesions disrupt simultaneous but not successive conditional discrimination learning of pigeons (Columba livia).

In 2 experiments we explored the effects of lateral versus medial laminar lesions of the hyperstriatum in pigeons (Columba livia); medical lesions were largely confined to the hyperstriatum accessorium, and lateral lesions to the hyperstriatum dorsale and hyperstriatum ventrale. In Experiment 1, lateral, but not medial, lesions disrupted acquisition of a simultaneous conditional discrimination; both medial and lateral lesions disrupted reversal of the discrimination. The reversal deficits of the medial and lateral groups were quantitatively similar, and both groups showed exaggerated positional responding. In Experiment 2, neither medial nor lateral lesions disrupted acquisition of a successive conditional discrimination. We conclude that lateral hyperstriatal damage does not obtain a general disruption of conditional learning; we speculate that the lateral hyperstriatum may play a critical role in configural learning.