Receptive-field organization of monkey superior colliculus.

A NUMBER OF recent studies suggest that the mammalian superior colliculus plays a crucial role in visually guided behavior (33, 35). Ablation experiments indicate that lesions in the hamster superior colliculus can cause severe deficits in orienting to visual and auditory stimuli while leaving intact the ability to discriminate pat serns in situ .ations in whi ch no orienting component is necessary for the successful performance of the discrimination (32). Related to this view is the idea that the colliculus plays an important role in the control of eye and head movements. After unilateral colliculectomy in the monkey, Denny-Brown (6) reports a fascinating cluster of eye-movement deficits. While the animal could look to either side or up and down, there was a slight divergent strabismus, and the optokinetic response was present only when the stripes entered the visual field from the operated side. Though the monkey could reach accurately for an object in the visual field contralateral to the lesion, he could not fixate the object, but only looked in its general direction. After bilateral colliculus lesions, monkeys showed fixed gaze, lack of reactivity to visual stimuli; lack of vocalization, and a variety of other deficits which led Denny-Brown to describe this structure as the “pattern setter of the nervous system.” Though other workers have failed to confirm the oculomotor deficits reported in this study (2, 28), recent work usi *g more sophisticated methods for head immobilization and eyemovement recording has confirmed and extended many of Denny-Brown’s original observations (M. Stryker, P. H. Schiller, and F. Koerner, unpublished observations). It