Reprints 121-144

Date:
1992-2001
Reference:
PP/CRI/M/1/7
Catalogue details

Licence: In copyright

Credit: Reprints 121-144. Source: Wellcome Collection.

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    The Problem of Consciousness It can now be approached by scientific investigation of the visual system. The solution will require a close %■' collaboration among psychologists, neuroscientists and theorists by Francis Crick and Christof Koch The overwhelming question in neurobi ology today is the relation between the mind and the brain. Everyone agrees that what we know as mind is closely related to certain aspects of the behavior of the brain, not to the heart, as Aristotle thought. Its most mysterious aspect is consciousness or aware ness, which can take many forms, from the experience of pain to self-consciousness. In the past the mind (or soul) was often re garded, as it was by Descartes, as something immaterial, separate from the brain but inter acting with it in some way. A few neuroscientists, such as Sir John Eccles, still assert that the soul is distinct from the body. But most neuroscientists now believe that all aspects of mind, including its most puzzling attribute—consciousness or awareness—are likely to be explainable in a more materialistic way as the behavior of large sets of interacting neurons. As William James, the father of American psychology, said a century ago, consciousness is not a thing but a process. Exactly what the process is, however, has yet to be discov ered. For many years after James penned The Principles of Psychology, consciousness was a taboo concept in American- psychology because of the dominance of the behaviorist movement. With the advent of cognitive science in the mid- 1950s, it became possible once more for psychologists to consider mental processes as opposed to merely observ ing behavior. In spite of these changes, until recently most cognitive scientists ignored consciousness, as did almost all neuroscientists. The problem was felt to be either pure ly philosophical or too elusive to study experimentally. It would not have been easy for a neuroscientist to get a grant just to study consciousness. In our opinion, such timidity is ridiculous, so a few years ago we began to think about how best to attack the problem scientifically. How to explain mental events as being caused by the firing of large sets of neurons? Although there are those who believe such an approach is hopeless, we feel it is not productive to worry too much over aspects of the prob lem that cannot be solved scientifically or, more precisely, cannot be solved solely by using existing scientific ideas. Radically new concepts may indeed be needed—recall the VISUAL AWARENESS primarily involves seeing what is di rectly in front of you, but it can be influenced by a three-di mensional representation of the object in view retained by the brain. If you see the back of a person's head, the brain in fers that there is a face on the front of it. We know this is true because we would be very startled if a mirror revealed that he front was exactly like the back, as in this painting, Repro duction Prohibited (1937), by René Magritte. modifications of scientific thinking forced on us by quantum mechanics. The only sensible approach is to press the experimental attack until we are confronted with dilemmas that call for new ways of thinking. There are many possible approaches to the problem of consciousness. Some psycholo gists feel that any satisfactory theory should try to explain as many aspects of conscious ness as possible, including emotion, imagina tion, dreams, mystical experiences and so on. Although such an all-embracing theory will be necessary in the long run, we thought it wiser to begin with the particular aspect of consciousness that is likely to yield most easily. What this aspect may be is a matter of personal judgment. We selected the mammalian visual system be cause humans are very visual animals and because so much experimental and theoretical work has already been done on it [see The Visual Image in Min d and Brain, by Semir Zeki, page 68]. It is not easy to grasp exactly what we need to explain, and it will take many careful experiments before visual conscious ness can be described scientifically. We did not attempt to de fine consciousness itself because of the dangers of premature definition. (If this seems like a cop-out, try defining the word gene—you will not find it easy.) Yet the experimental evi dence that already exists provides enough of a glimpse of the nature of visual consciousness to guide research. In this article, we will attempt to show how this evidence opens the way to attack this profound and intriguing problem Visual theorists agree that the problem of visual con sciousness is ill posed. The mathematical term ill posed means that additional constraints are needed to solve the problem Although the main function of the visual system is to perceive objects and events in the world around us, the in- FRANCIS CRICK and CHRISTOF KOCH share an interest in the experimental study of consciousness. Crick is the co-discoverer, with James Watson, of the double helical structure of DNA While at the Medical Research Council Laboratory of Molecular Biology in Cambridge, he worked on the genetic code and on develop mental biology. Since 1976, he has been at the Salk Institute for Biological Studies in San Diego. His main interest lies in under standing the visual system of mammals. Koch was awarded his Ph.D. in biophysics by the University of Tübingen. After spend ing four years at the Massachusetts Institute of Technology, he joined the California Institute of Technology, where he is now associate professor of computation and neural systems. He is studying how single brain cells process information and the neu ral basis of motion perception, visual attention and awareness. He also designs analog VLSI vision chips for intelligent systems.