The search for consciousness: Scientists and philosophers joined forces to find out how human minds work. Andrew Brown reports

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The Independent Online
PUTTING a ghost detector into an intensive care ward sounds like the worst possible kind of scientific frivolity. Next thing you know, psychologists will tell us that students given repetitive tasks in a boring environment find that their minds wander, or that rats fed amphetamine show schizophrenic symptoms.

And in fact all these results were presented at a symposium on the physical basis of consciousness, held in London last week; and all of them may matter tremendously because they are steps in understanding how brains and minds fit together.

The meeting brought together philosophers who think about minds with psychologists and neurologists who know about brains. All were united by an ambition to bring consciousness inside the scope of traditional science, to the point where you could look at a brain and see how a mind works just as you can look at the chemistry of a DNA molecule and see how life works.

To do this, you need to know how minds work, how brains work, and how these two things (or whatever they are) might fit together. That is why it is scientifically worthwhile to give rats amphetamine and see how it affects their learning abilities. The result is that it makes them mimic a way in which schizophrenics learn faster than normal people.

Dr Jeffrey Gray, of the Institute of Psychiatry in London, said that the meeting had persuaded him he may have found the brain architecture that underlies consciousness as a result of his experiment on rat learning. His theory says that there is a constant loop of information between the limbic forebrain and the basal ganglia. The basal ganglia sends messages about the state of the world to the limbic forebrain, where they are compared with a model of how the world is expected to be. If the comparison checks out, then the message goes back: 'OK, do the next thing,' and this is passed on by the basal ganglia to the motor apparatus. If not, action is taken.

Dr Gray says that schizophrenia may result from a breakdown in this circuit: the brain of the schizophrenic fails to recognise anything as familiar. Because everything appears new and startling to the schizophrenic, he invents vast and convoluted explanations for the significance of everyday objects. But the same process makes schizophrenics quicker to learn in some situations. Post-mortem examinations on the brains of schizophrenics show changes in the limbic forebrain. This should be connected to particular chemical imbalances in the basal ganglia, according to Dr Gray's theory. These chemical changes can also be produced by the action of amphetamine in rats; and rats so treated do show exactly the same increase in some learning capacities. So he believes his theory may have shown where in the brain consciousness resides. But, even assuming he is right, there is an enormous snag. In Dr Gray's words: 'Nothing in the account of the neuropsychology of schizophrenia that I have sketched gives the slightest clue why any of the events in the brain should achieve or cause any form of conscious experience.'

In other words, we may know where it is happening, but we still are no closer to understanding what it is.

'I'm not saying that I have a theory of how the brain generates consciousness: that awaits its Einstein,' Dr Gray said.

But the localisation of particular mental activities to particular parts of the brain can be precise. Dr Bill Newsome, of the University of California, has found a particular area in the brains of macaque monkeys which tells them in which direction what they see is moving. By applying an electric current there, he can apparently persuade a monkey that a pattern moving downwards is actually moving up.

For ethical and legal reasons this kind of research is almost impossible to do on humans. None the less, some brain surgery patients have been the subjects of similar experiments. In California, there are patients who control chronic pain by stimulating electrodes in their brain.

The philosophical implications of all this divided the conference sharply. No one there believed in 'soul' or 'spirit' as a separate substance to the mind. But just in case consciousness should turn out to be something separable from brains, there is the ghost detector test.

Somewhere in an English coronary unit there is an optical illusion that can only be seen from the ceiling. If anyone comes back from a near death experience, and describes 'seeing' it, then all the theories above will be in real trouble. But spiritual explorers had better hurry - funding of the experiment runs out in six months.