Science: The Truth About... Consciousness

CONSCIOUSNESS - THAT amorphous entity that makes us aware of who we are - has become the subject of intense scrutiny by scientists who are beginning to tread on territory once the sole preserve of philosophers. Some of the greatest minds in science, including the great Francis Crick, co-discoverer of the structure of DNA, have now begun to tackle perhaps the greatest mystery of the human brain.

Rene Descartes, the great 17th century French philosopher and scientist, coined what has probably become the most enduring short-hand description of consciousness: ``I think, therefore I am''. This notion of a single, unified state of conscious-ness has, however, come under attack from eminent brain researchers who have studied the way the human brain responds to visual information.

According to this radical theory, human consciousness is composed of several, interacting states of consciousness that have to be marshalled together to give us an impression that we are just one person. A better description of consciousness would, if this is true, be something like ``we think, therefore I am''.

Semir Zeki and Andreas Bartels, from the Wellcome Department of Cognitive Neurology at University College London, believe there are many ``micro'' consciousnesses in the human mind that are brought together to form a single awareness of the outside world. Professor Zeki, a world authority on the way the brain handles visual information, said his work has shown that the mind uses several conscious states to become aware of the different visual facets of one object.

``If you think of a green bus moving from right to left, the brain handles the bus's colour, shape and its movement in different ways. In other words we are separately conscious of each element that makes up the bus,'' Professor Zeki says.

He cited the example of some people who become blind but are still fully conscious of colour. Some victims of smoke inhalation, which causes oxygen starvation to the brain, become blind but can still see colour just as well as they had before. ``I wouldn't say that Descartes has got it wrong. What he did was to get people to concentrate on a single entity of consciousness, which turns out to be wrong,'' Professor Zeki says.

The new hypothesis, published in the Proceedings of the Royal Society, is based on experiments showing that people become aware of the colour, shape and movement of a single object at slightly different times - a few thousandths of a second in fact.

A single consciousness, as envisaged by Descartes, would mean all the different attributes of a moving bus would be handled by the brain at precisely the same time. As this is not the case, there must be many, smaller conscious states working in unison. It means that consciousness is distributed throughout the brain and is asynchronous - it occurs at different times,'' Professor Zeki says.

The scientists do not profess to have solved the mystery of consciousness - far from it, they say they have only scratched the surface - but their experimental insight might eventually prove to be more productive than the philosophical ramblings of scholars over the centuries.