Phosphenes have been produced by direct stimulation of the dorsal mesencephalon in the region of the superior colliculus of an alert man. Electrodes were implanted in the midbrain for the purpose of localizing the ascending sensory pathways in a patient who was suffering from intractable phantom limb pain prior to a stereotactic lesion to relieve the pain. One electrode was situated just beneath the left colliculus. Electrical bipolar stimulation was done over a period of several weeks and resulted in the patient experiencing phosphenes in the contralateral visual fields which were associated with lateral conjugate eye movements toward the side of the visual phenomena. These observations point to the possible role of superior colliculus in the organization of visual phenomena in man.
Nashold BS. Phosphenes Resulting From Stimulation of the Midbrain in Man. Arch Ophthalmol. 1970;84(4):433-435. doi:10.1001/archopht.1970.00990040435006