The Zombie Within

Consider the following situation: You see an outstretched hand, but instead of shaking it immediately, which instinct would dictate, you are required to close your eyes and wait several seconds before doing so. Koch and Crick suspect that without a short-term memory, a zombie could not do this task, or any other in which an artificial delay was imposed between “an input and the associated motor output.” Absence, like presence, has a neurological signature, and Koch imagines a kind of “conscious-ometer” that could be used to measure who and what is consciously aware.

One immediate application would be anesthesiology: When is a patient about to undergo surgery truly out? But in The Quest for Consciousness, due out in January, Koch also suggests more controversial applications. When does consciousness arise? he asks. Is it present in the newborn child? Or does it gradually emerge? And if so, at what stage in the infant’s development? At the other end of life’s continuum, does consciousness gradually fade as dementia sets in, or does it linger in diminished form until the bitter end? With an operationalized test, he writes, we could “monitor the presence of consciousness in premature babies and young infants, in patients whose minds are afflicted with severe autism or senile dementia, and in patients who are too injured to speak or even to signal.” As a practicing Catholic who attends Mass every Sunday, Koch is haunted by the question of life’s end; his father died while suffering from Parkinson’s disease, and that long drawn-out mental decline etched itself deeply into his son’s psyche. “Wouldn’t you want to know if someone you loved was conscious or not?” he demands.

A conscious-ometer could also be applied to animals. Every morning Koch goes running with one of his three large dogs, and there is no doubt in his mind that they are extremely aware. How far down the animal kingdom does the trait extend? “Is a fly conscious?” Koch asks. “Is a bee?” Recent evidence from an Australian researcher reveals that bees possess an ability to learn complex navigational cues: Koch suspects that to some extent they must be aware.

Koch’s conscious-ometer is more than a mere thought-experiment; he genuinely hopes to build one. For the moment, he is concentrating not on humans but on biology’s most common test subject, the mouse. He and his colleagues are trying to develop “a mouse model of consciousness,” a rigorous way of determining if and when a mouse is aware. Over the past decade, biologists have learned how to turn individual genes on and off in the developing rodent fetus. With a mouse model of consciousness, Koch could begin to explore what genes are essential for this phenomenon. One question he would like to pursue is whether it is possible to genetically engineer an animal without conscious awareness — a zombie mouse.

Several years ago, Koch tells me, one of his best friends, a schizophrenic, committed suicide. It was an act that he finds almost incomprehensible and, as a Catholic, deeply disturbing. “If we want to understand the human mind and all the suffering it is subject to, then we have to understand its physiological basis,” he says, his voice rising with a sense of urgency. Koch ends his book with a call for a scientific theory “that accounts for what organisms, under what conditions generate subjective feelings; what purposethey serve, and how they come about.” Whether science can finally breach the gap between “matter” and “mind” — a category division that some argue is a disaster of its own making — remains to be seen. Two thousand years of history suggest the problem has depths that will not easily be plumbed by any physiological probe. But if in the 21st century somebody finally does understand the emergence of consciousness from the neurochemical mass of our brains, he or she will no doubt owe a debt to Christof Koch.

Human beings are exceptionally good at visual perception — we can easily distinguish among thousands of faces, even ones we’ve never seen before. The best computer vision systems struggle with this problem and are usually fooled by simple disguises, or merely a change in lighting. How do our brains piece images together? What is going on at the neuronal level that makes us so skilled at this task? For years, vision researchers have been experimenting with animals, including monkeys, measuring the output from single neurons through probes embedded in their brains.

But you can’t stick probes into human brains — at least not under normal circumstances. There is, however, a small cohort of epileptics whose condition requires surgery, and in preparation for that procedure electrodes are implanted beneath their skulls to gather information about the seizures. Such patients provide a unique opportunity for researchers to observe brain function directly. Christof Koch’s graduate student Leila Reddy has been working with a group of such patients at UCLA’s Cognitive Neurophysiology Laboratory under renowned surgeon Itzhak Fried.