Association brain systems and visually guided movements in the cat.

A study was made of contribution made by specific and association systems of the brain to the organization of visually guided movements in cats. Animals were trained to make two light spots coincide; one of them was guided by pressing the pedal. Ablation of specific visual areas of the neocortex did not affect the performance, whereas local lesions of association frontal and parietal areas caused severe deficits of visuomotor integration. Patterning of new programs compensated for the deficits. Destruction of the ventrolateral nucleus (VL) of the thalamus which is responsible for information transfer to association area brings about irrevocable impairment to the movements learned. Coagulation of ventral or dorsal portions of VL in trained cats specifically encroached the performance. In the former case, fast ballistic movements towards the target are affected, whereas in the latter tracking movements were disturbed. It is supposed that VL is a link between the two association systems, the interplay of which provides for activities of the mechanisms involved in sensory control of goal-directed movements.