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Publisher Summary The main function assigned to the superior colliculus is saccadic redirection of the eyes and/or head toward a suddenly appearing visual or other stimulus. The effects of damaging or stimulating the superior colliculus in rodents have demonstrated its involvement in a wide variety of responses appropriate to novel sensory stimuli. These responses are: (1) Approach movements: these movements are directly influenced by stimulation parameters. Thus, the superior colliculus control their velocity and amplitude independently. (2) Avoidance and escape responses: the movements are elicited from rodents by naturally threatening visual stimuli and are also produced by appropriate electrical or pharmacological stimulation of the superior colliculus, and impaired by collicular damage. (3) Physiological responses: naturally occurring approach and avoidance movements are typically accompanied by a range of physiological reactions, which are also elicited by stimulation of the superior colliculus. The chapter discusses that if different collicular output channels are functionally distinct, they might be expected to have distinctive patterns of sensory and non-sensory input. In rat, the rostrolateral intermediate layers and the associated tecto-medullary projection are concerned primarily with non-saccadic head movements, whereas the tecto-periabducens projection is be more concerned with saccadic movement. |
