Francis Crick (1916-2004) was a theoretical and molecular biologist who co-discovered the structure of DNA and helped elucidate how the genetic code is expressed in protein synthesis. At the age of sixty turned his interest to neuroscience and, after ten years of study, began to address the problem of consciousness. His last book, The Astonishing Hypothesis: The Scientific Search for the Soul, published in 1995, provides not only the most lucid description I have read of the neurobiology of visual perception, but also an experience of how he thought about difficult biological problems. What Crick has to say about the complex multi-leveled systems involved in visual perception is fascinating, though dated. Here I will focus on how he approached the problem of consciousness and what that might say about how we think about psychiatric problems.
Crick argued against trying to define consciousness precisely until its workings were better understood; he believed the neural mechanisms, once they were clarified, would enable meaningful definitions of the various types of consciousness.
Crick agreed with the basic concept of the brain I discussed last week in my post about Eric Kandel’s work . In Crick’s view, our brains evolved to pack astonishing amount of computing power into a small space using very little energy. He quotes the psychologist V.S. Ramachandran: the brain “uses rules of thumb, short-cuts, and clever sleight-of-hand tricks that are acquired by trial and error through millions of years of selection.” It uses constraints, i.e. built-in assumptions about how information should be interpreted, to construct and analyze images. He notes that such ad-hoc mechanisms often work better than those designed for specific purposes. I would add that they are more adept at handling new information and adapting to changing conditions.
Crick identified several forms of awareness—seeing, thinking, emotions, pain, etc.—and hypothesized that one or a few basic mechanisms may underlie them all. He made the strategic decision that studying visual perception would be the most productive approach, since understanding how we become aware of what we are see might provide organizing principles applicable to other aspects of consciousness.
Drawing almost entirely on experimental work by others, he identified numerous processes at various stages of visual perception. “The whole system,” he wrote, “does not look like a one-shot, static, response system. It is likely to operate by many transient, dynamic interactions, conducted at a fairly fast rate.” These are organized in, many of which communicate with each other bi-directionally: “The general pattern, then, is that each area receives inputs from several lower areas. It then operates on this combination of inputs to produce even more complex features, which it then passes on to even higher levels in the hierarchy.”
Crick was always on the lookout for larger-scale hypotheses, though from what he came up with for the most part had to do with intermediate levels of brain organization. Regarding the cellular layers of the cortex, he wrote: “This tempts one to a broad generalization that goes far beyond the present evidence. This is that the activities in the upper cortical layers are largely unconscious, while at least some of those in the lower layers correspond to consciousness. I must confess to being unreasonably fond of this hypothesis—it would be so pretty if it were really true.”
What does this tell us about neurobiology and clinical psychiatry? First, for purposes of understanding the mechanisms involved, it may not be useful to argue about precise definitions of diagnostic diagnoses like depression or psychosis, clinical phenomena such as attention or empathy, or therapeutic processes like cognitive therapy or desensitization until we have a better understanding of the brain. These concepts are necessary for clinical work, but at this point we can’t know what they mean in biological terms.
Crick chose to study visual perception rather than overall consciousness or some other type of awareness because he had access to more information about the visual system. What areas of psychiatric interest are most available for study now? I’m not sufficiently up to date to comment expertly, but here are a few thoughts. Among psychiatric disorders, addiction is best understood neurobiologically, though much more research into its mechanisms is needed. Significant work is under way in the areas of anxiety and autism. Attention, which is closely related to working memory and to consciousness itself, is a complex phenomenon, and, while some information is available about how stimulant medication helps attention, it may be some time before we understand attention in detail. While the role of biogenic amines in mood disorders was discovered over fifty years ago, and more recently depression has been associated with effects of stress hormones on the hippocampus, our understanding is certainly incomplete. As I have noted, very exciting research on empathy and relatedness is taking place, but empathy too is a complex, multilevel phenomenon involving several neural systems.
There does seem to be room for creative application of neuroscientific discoveries in new areas. Kandel’s attempt to draw on the neuroscience of both visual perception and emotion to understand how we behold art, which I discussed last week, is an example. It is even possible that such efforts might generate new hypotheses about underlying neural mechanisms.
Thirty years ago Crick immersed himself in the visual system to see how far he could go in explaining consciousness. He was able to learn a great deal and explain it well. He did not discover the kind of concrete mechanisms he found in the structure of DNA and in the transcription of DNA to RNA and then to proteins—the brain turned out to be far more complex. His work on consciousness, nevertheless, is an example of how a brilliant mind approaches a difficult problem and may provide some guidance as we apply emerging neuroscientific discoveries to clinical psychiatry.