Structures involved in acquisition and performance of visually guided movements in the cat.

Cats were trained to press on a lever either fixed or moving at different speeds from left to right or right to left at random. In the first series of animals, the following bilateral lesions were performed after reaching criterion on the moving lever: (1) deep cutting of cortico-cortical fibers connecting visual and frontal cortex; (2) subtotal electrolytic destruction of n. ventralis lateralis of the thalamus (nVL); (3) ablation of the anterior (3a) or middle (3b) suprasylvian cortex. No postoperative deficits were noticed after lesions (1), (2), (1 + 2) or (3b). On the other hand, impairment was found after lesion (3a), strongly suggesting the role of the anterior suprasylvian cortex in visual guidance of the forepaw movement in cat. The second group of animals was first trained to press the fixed lever and then underwent bilateral n. VL lesions. After lesion, performance with fixed lever remained normal while the animals displayed a deficit with the moving lever. The conclusion is that the n. VL is essential only during the acquisition phase of the tested visuomotor performance.