Some scientists believe the eye is the window of the mind; others think that the way our brain cells react in patterns may govern consciousness. Concluding our series, we consider recent research consider recent research
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"EVERYTHING in my field of vision wavered and was distorted as if in a curved mirror. Pieces of furniture assumed grotesque, threatening forms and my neighbour was no longer a friendly woman but a malevolent, insidious witch with a coloured mask. Even worse than the demonic transformations of the outer world were the alterations I perceived in myself, in my inner being. A demon had invaded me, taken possession of my mind, body and soul. I was seized by the dreadful fear of going insane."

As it turned out, it was not insanity that had turned Albert Hofmann's mind upside down and inside out, but the hallucinogenic drug LSD. As a 37-year-old researcher working for Sandoz, the Swiss chemicals company, Hofmann was in 1943 the first person to take a trip on lysergic acid diethylamide. As his notes indicate, it became a frightening ride into the inner recesses of the human mind. Even in 1993, he could still recall his fear of events that took place half a century ago. "That was a horrible, terrible, terrible experience. I had the feeling of being out of my body, of being insane, of having lost all connection with reality," he told me.

It is clear from the experiences of those who have taken mind-bending drugs that human consciousness is not a single, inviolate entity. Chemicals can and do alter the doors of perception in quite disturbing ways. As Aldous Huxley once said of mescaline, the hallucinogenic drug derived from cactus plants, it is not for people who want to be in control of life, but for those who want to be at the mercy of a set of unbridled consciousnesses all clamouring for attention. The effects of hallucinogens on the brain is one of the principal pieces of evidence we have that consciousness can be related to the mysterious chemical events taking place in our heads. These drugs show that consciousness has a physical basis and is not merely a metaphor to describe how we describe ourselves. They demonstrate it is a product of brain chemistry that can be altered in a haphazard, uncontrollable manner by alien molecules.

Defining consciousness is inherently difficult. Most of what we know about it comes from knowing what it is not. Being sound asleep isn't being conscious, neither is lying on an operating table under anaesthesia, and consciousness has certainly nothing to do with being in a coma or being brain dead. "There's quite simply nothing else like it, so you can't define it in terms of anything," says Susan Greenfield, a brain researcher at Oxford University who has just written a book on consciousness. Most things can be defined in terms of a "superset", so that a table becomes a piece of furniture, an eye becomes a sensory organ or a cat becomes a four-legged animal. This proves impossible for consciousness, which is best described simply as a "property of the brain", Dr Green-field says. As one American psycho-logist remarked a century ago, consciousness is not a thing but a process.

Only a few years ago the very thought of studying consciousness in an empirical way would have been treated with deep scepticism by scientists. This is beginning to change now that so much else is being revealed about the brain with the help of scanners, which have opened windows into the human mind. Scientists in a suprisingly wide range of disciplines feel that this nebulous concept of consciousness cannot for much longer remain a taboo subject merely because it is difficult to know what it is, let alone know how to measure and observe it. Francis Crick, who discovered the DNA double helix with Jim Watson in the 1950s, believes that human consciousness, the mind's "most puzzling attribute", is now ripe for study. "The overwhelming question in neurobiology today is the relation between the mind and the brain," he says.

Crick is particularly interested in the way the brain handles visual information, almost certainly one of its most complex tasks. Being able to see and process visual data from the environment is one of the most obvious signs of being aware of yourself and the wider world. In simple terms, Crick and his colleague Christof Koch, of the California Institute of Technology, believe that understanding the secret of vision will lead to a breakthrough in understanding how physical and chemical events in the brain relate to our subjective sensations. It will, they say, lead us to know how the brain relates to the mind.

Most scientists, including Crick and Koch, who talk about how the brain deals with vision quote the pioneering work of Semir Zeki, professor of neurobiology at London University. Zeki used brain scanners to elucidate the role played by a convoluted array of nerve signals in perceiving and understanding information from the eyes.

Up to the mid-1970s, it was fashionable to describe vision as two separated entities. There was sensing and there was understanding, each with a separate "seat" in the brain's cortex, its outer region which controls many of the higher intellectual functions. Zeki showed this was far too simplified. In experiments with volunteers placed in a PET scanner (which measures blood flood in the brain) Zeki found that a Mondrian painting, containing lots of colour but no movement, stimulated one area of the brain, whereas moving, black-and-white squares caused another area to "light up". It was evidence that the brain separated different aspects of vision - motion and colour in this example - rather than simply seeing and understanding.

Zeki used the same technique to study the peculiar phenomenon known as "blindsight". These patients can "see" but cannot understand. They are in fact totally blind, having suffered damage to an area of the brain which is essential for vision. The reason they are described as being able to see is because when forced to make a decision on something before their eyes - for instance the direction of a moving light - they invariably get it right, even though they say they cannot see anything. They are simply not conscious of what they can see.

This would appear to confirm the old notion that seeing and understanding are separated, but Zeki says it is more complicated. What he was able to demonstrate is that there is a two-way dialogue between different areas of the brain involved in vision, with one influencing the other and vice versa. Seeing and understanding are taking place simultaneously in different areas, and one brain region does not "report" to another in a hierarchical fashion. This suggests that there must be physical connections between different vision areas, with signals flowing in opposite directions on different nerves. This is precisely what Zeki has found, a discovery which has profound implications for consciousness because, as he says, "our inquiry into the visual brain takes us into the very heart of humanity's inquiry into its own nature".

Seeing is believing, which is why vision is so important for the study of consciousness. But there is another aspect of the mind that is equally important for our concept of ourselves and the world around us: memory. Susan Greenfield says that it is no rash claim to suggest that certain memory impairments give rise to radically modified states of consciousness. Sudden amnesia is a dramatic example of how consciousness can change with memory.

"Memory is so interlinked with consciousness that it cannot be regarded as a distinct function and housed in a special place," Dr Greenfield says. It is fair to say that when someone is anaesthetised or deeply asleep, and not dreaming, they have no consciousness and no memory. One goes with another, in the way that being conscious of the sensation of cold ice cream on a sunny day in a park full of children may invoke the memory of one's own childhood. As Professor Steven Rose, who researches memory at the Open University, says: "Many people find the study of memory as a way into the study of consciousness."

He, like many brain researchers, has found that a phenomenon common to many animals, including humans, may have something to do with consciousness. This is the finding that brain cells often oscillate in terms of the nerves' firing rates at a frequency of 40 times a second. "There are particular regions of the brain in which there are bursts of firing of cells at the rate of 40 hertz. It seems to occur dramatically when memory and learning are taking place," Rose says. Memory and learning are in general terms part of the conscious process, so perhaps this oscillating frequency is a feature of it? Crick and Zeki suggest it might be.

Susan Greenfield is not so sure. She is working on a radical view of consciousness that embodies something she calls "neuronal gestalts". She takes the name from the German word for pattern, meaning that the result of all the brain cells, neurons, and their electrical and chemical activity is greater than the total sum of the parts. An oval, two dots and a straight line when they are put together in the configuration of a face have a particular meaning, but on their own they are simply an oval, two dots and a straight line.

The same is true of consciousness, she suggests. Stimulation of neurons in the brain leads to a gestalt that ripples out from an epicentre, like a raindrop sending out ripples in a puddle. Consciousness can be seen as a series of gestalts all vying for attention, says Dr Greenfield: "As varying degrees of new sensory information come in, as our internal body environment fluctuates in its levels of glucose, hormones and so on, and as the ripples of one gestalt spread out to even more remote associations, so a new epicentre starts to recruit neurons into a gestalt. This new gestalt supplants the original, and our consciousness subtly shifts." This is perhaps what happens when the noise of car brakes screeching past the window stops us momentarily from reading a newspaper, allowing a hunger gestalt to gather momentum, saying it's time for lunch, forget the paper.

"Consciousness grows as your brain grows and the more complex the brain, the deeper the consciousness," Dr Greenfield says. The idea can be extended to explain the behaviour of children, schizophrenics and manic depressives. Children have smaller gestalts than adults and so are easily sidetracked, but when a gestalt happens it quickly dominates everything else, resulting in overwhelming joy or overwhelming sadness. "It fits perfectly because they have smaller brains," she says.

Schizophrenics also have abnormally small gestalts, which makes them deeply conscious of every minor sensory input where "everything has signficance", Dr Greenfield says. As a result, one train of thought impinges on another, as a schizophrenic patient, unable to ignore the sensory input of a picture on the wall, remarked: "I feel so bad even the picture has a headache." It is intriguing that the effects of hallucinogenic drugs have often been used as models to explain schizophrenia; again, this fits in neatly with Dr Greenfield's gestalts theory. "The central problem with hallucinogenic drugs is that either the person is overly obsessed with an object or thought or is too readily distracted along some tangential and idiosyncratic pathway."

Manic depressives present a different problem. Their gestalts are abnormally large and can dominate their consciousness, resulting in lethargy and brooding. "I would say that a large gestalt is necessary for depression, not a cause of depression," she says. Vigorous exercise or doing something that is unusually exciting, like bungee-jumping, is a way of forcing small gestalts on the brain because it involves a lot of extra sensory input into the brain, creating epicentres for new gestalts to form. This may be why depressive people often benefit from getting out and being active, Dr Greenfield says.

In this view of consciousness, we are constantly being cajoled in one direction or another by waxing and waning gestalts that ripple across and through our brains like phantom bursts of energy. It is certainly a very neat idea and one that may come close to the truth. But should the day come when science can understand, really understand human consciousness, there would be almost unimaginable ethical difficulties, which worries Dr Greenfield. "We're all saying we'd like to understand how the brain stimulates consciousness, but imagine if we could do that, what would be the implication? We'd annihilate the individual. If we knew how the brain generated consciousness exactly, then we could manipulate it exactly. I could hack into your consciousness, you could hack into mine. You won't have the individual any more."

Such thoughts are inherent to the study of the structure that itself gives rise to our thoughts. Dr Greenfield, like many others studying the brain, is deeply aware that their attempts at understanding human consciousness are breaking new intellectual ground and are loaded with irony. "What's so freaky is that the brain is trying to understand itself. This is what's so weird. It's a rather spooky thought, the more you think about it."

Think about it. !


Journey to the Centres of the Mind, by Susan A. Greenfield, W H Freeman, pounds 17.95.

An Astonishing Hypothesis - the scientific search for the soul, by Francis Crick, Simon & Schuster, pounds 6.99 (paperback).

Drugs and the Brain, Solomon H. Snyder, W H Freeman, pounds 19.95.