Unilateral subtotal collicular and, large but not small, unilateral posterior cortical lesions in rats produced ipsiversive progression tendencies in a visual task. However, no support could be given to the view that the progression tendencies following unilateral collicular lesions are in part a reflection of contralateral visuosensory-field deficits. Thus, performance of a light-dark task was equally good when vision was restricted to the eye leading to the damaged colliculus as when restricted to the eye leading to the undamaged collicullus. la addition, bilateral collicular lesions had no effect on performance of either the light-dark or a stripes discrimination task. The study indicated the need for caution in basing interpretations of the nature of vision on simple response tendencies.

Visual decortication failed to affect rate of acquisition of 1-min. delayed CERs when either light alone or noise alone provided the CS. However, CER paradigms involving a combination of light and noise CSs revealed differences in behavior between experimental and control animals. Decorticate rats transferred the CER from light to noise (although not from noise to light). Normal animals showed no transfer. Decorticate animals were conditioned to a noise CS in a paradigm which prevents conditioning in normal subjects. Also, decorticate rats were better able to discriminate a compound light-noise CS from light-alone and noise-alone CSs. Partly from these findings, partly because the abnormal behavior of the decorticate subjects is mimicked by normal animals wearing light-diffusing eye occluders, and partly from other considerations, it was speculated that vision as a qualitatively unique sensory modality is undermined by visual cortex destruction.The nature of vision in animals lacking visual cortex appears to be in dispute. Kliiver's (1942) study, considered by some to be the classic one in the field, suggests that the visually decorticate animal is reduced largely to the use of luminous flux cues. However, work prior to Kliiver's study (e.g.,