Self Comes to Mind

in addition to a map of the visual world, topographical maps of auditory and somatic information, the latter hailing from the spinal cord as well as the hypothalamus. The three varieties of maps—visual, auditory, and somatic—are in spatial register. This means that they are stacked in such a precise way that the information available in one map for, say, vision, corresponds to the information on another map that is related to hearing or body state. 13 There is no other place in the brain where information available from vision, hearing, and multiple aspects of body states is so literally superposed, offering a prospect of efficient integration. The integration is made all the more significant by the fact that its results can gain access to the motor system (via the nearby structures in the periaqueductal gray as well as via the cerebral cortex).
    The other day a nice little lizard on my terrace was darting about in hot pursuit of a silly fly that insisted on buzzing him, flying dangerously low. The lizard tracked the fly perfectly and finally caught it with its tongue, thrown out at the precise moment. The collicular neurons plotted the moment-to-moment position of the fly and guided the lizard’s muscles accordingly, eventually dispatching the tongue when the prey was within reach. The adaptive perfection of this visuomotor behavior to its environment is astounding. But now imagine the rapid, sequential firing of the neurons in the lizard’s superior colliculus, astound yourself some more, and pause for a second to wonder. What did the lizard see? I would not know for certain, but I suspect he saw a black moving dot, zigzagging in an otherwise vague field of vision. What did the lizard know of the ongoing event? I suspect nothing, in our sense of knowing. And what did he feel when he was eating his hard-won lunch? I suspect that his brain stem registered the successful completion of its goal-directed behavior and the results of an improved state of homeostasis. The substrates of the lizard’s feelings were probably in place, although he could not reflect on the remarkable skill he had just displayed. It is not always easy being green.
    This powerful integration of signals serves an obvious and immediate purpose: the gathering of information necessary to guide effective action, be it movement of the eyes, the limbs, or even the tongue. This is achieved by rich connections from the colliculi to all the brain regions required to guide movement effectively, in the brain stem, in the spinal cord, in the thalamus, and in the cerebral cortex. But besides achieving effective guidance of movement, it is possible that there are “internal,” mental consequences of this useful arrangement. In all likelihood, the integrated, in-register maps of the superior colliculus generate images as well—nowhere as rich as those made in the cerebral cortex, but images nonetheless. Some of the beginnings of mind are probably to be found here, and the beginnings of self might be found here too. 14
    What about the superior colliculus in humans? In humans, selective destruction of the superior colliculus is rare, so rare that the neurologic literature records a single case, of bilateral damage, fortunately studied by a major neurologist and neuroscientist, Derek Denny-Brown. 15 The lesion was the result of trauma, and the patient survived for months, in a severely impaired state of consciousness that best resembled an akinetic mute state. This is suggestive of a compromise of mentation, but I must add that on the occasion I encountered a patient with collicular damage, only a brief disturbance of consciousness was detectable.
    Seeing with the colliculi alone once the visual cortices are lost possibly consists of sensing that some unspecified object X is moving in one of the quadrants of vision, say, away from me, or that it is coming closer to me. In neither case will I be able to describe what the object is mentally, and I may not even be conscious of it. We are talking here of a very vague mind, gathering sketchy information about the world, although the fact that the images are vague and incomplete does not render them useless or unhelpful, as blindsight shows. However, when the visual cortices are missing from birth, as in the hydranencephalic cases described earlier, both the superior and the inferior colliculi may make more substantial contributions to the mind process.
    I must add one last fact to the evidence in favor of