The superior colliculus simultaneously modifies the responses of the lateral geniculate cells and of the oculomotor nuclei.

Descending and ascending influences of the superior colliculus (CS) were studied in the following way. In anesthetized and paralyzed rabbits two tungsten micro-electrodes were lowered in the (CS) and the Lateral Geniculate Nucleus (LGN) for single unit recordings. A third semi-micro-electrode (dia. 100 microns) was positioned in the vicinity of the oculomotor nuclei. The final position of this electrode was determined at a location which yielded an eye movement with the lowest intensity of the electrical pulse. The typical experimental procedures required that a spontaneous collicular spike triggered the flash presentation and data acquisition. Results indicated that collicular endogeneous activity may be capable of modifying simultaneously the evoked neuronal responses of the LGN and in the vicinity of the oculomotor nuclei.