Visual discrimination between spatially separated stimuli by cats with lesions of the superior colliculus-pretectum.

(1) This study was designed to test the ability of cats with lesions of the superior colliculus-pretectum to discriminate between stimuli which are widely separated in space. (2) Intact cats and cats learning or relearning after lesions of the superior colliculus-pretectum, were trained on light-dark (LD) and horizontal-vertical stripe (HV) discriminations in a V-maze, where the stimuli were widely separated in space, or in a divided straight maze, where the stimuli were side by side. (3) Two types of errors were scored: door-push errors when the cat pushed open the incorrect door; alley-entrance errors when the cat entered the incorrect alley, but turned and entered the correct alley without having pushed the incorrect door. (4) In the V-maze as well as in the straight maze, cats with lesions of the superior colliculus-pretectum achieved criterional performance by alley-entrance and door-push scoring on LD and HV discriminations. Thus, cats with lesions of the superior colliculus-pretectum can locate or orient to widely separated visual stimuli well enough to discriminate between them from a distant choicepoint. (5) Cats with lesions of the superior colliculus-pretectum generally committed a larger number and higher percentage of alley-entrance errors during learning than unoperated cats in either maze. However, commission of alley-entrance errors was not further increased in the V-maze, where the stimuli were widely separated in space. (6) All unoperated cats committed alley-entrance errors as well as door-push errors suggesting that commission of alley-entrance errors may reflect a normal process in two-choice learning.