The essence of being
Try defining consciousness and, like the proverbial 6 blind men trying to describe an elephant, you end up with an embarrassment of choices. Is it a complex symphony created by a neural orchestra, a grand equation arrived at by the logical computations of the brain, a confidential world authored by sensations, or some metaphysical entity, call it soul or atman, that bathes the entire universe? Says philosopher Julian Jaynes: "When asked the question 'what is consciousness?' we become conscious of consciousness. And most of us take this consciousness to be what consciousness is. This is not true."
Frustrated philosophers have suggested several answers, two of which have attracted attention. You either assume that consciousness is just not in the brain, as suggested by Rene Descartes, the 17th century philosopher-mathematician, when he separated the mind from the brain: Cogito, ergo sum (I think, therefore I am). Or assume that consciousness is nothing but a more exalted feature of the brain's circuitry.
Though it remained a popular notion till the early part of this century, the mind-brain divorce wasn't particularly satisfying. It implied that the mind may be anywhere in the universe, floating around, connected in some mysterious way to corporeal craniums. A meticulous doubter, Descartes saw this difficulty, and hastily proposed the idea that the mind is parked in the pineal gland, a small undistinguished corner in the labyrinth of the brain.
Descartes' solution to the mind-body problem is now more or less passe. A widely accepted notion today is that all features of mind, including its most intriguing attribute--consciousness or awareness--are the visible patterns of a kaleidoscopic interplay of the subterranean neurons. As William James, the father of American psychology, put it: "Consciousness is not a thing, but a process."
But the process of how the water of the physical brain is transformed into the wine of consciousness is still shrouded in mystery. Till recently, most cognitive scientists ignored consciousness, as did almost all neuroscientists. The issue, says Francis Crick, co-discoverer of the double helix structure of the lifegiving DNA, was felt to be either purely 'philosophical' or too elusive to study experimentally. The trouble with consciousness is that it is private; there are no analogies from our shared concepts of the physical world adequate enough to describe our experience of consciousness, or of what we take to be ourselves.
The decade of the brain In recent years, using voyeuristic techniques, such as positron emission tomography (PET) and magnetic resonance imaging (MRI), biologists have begun to investigate mental phenomena such as memory, emotions, perception, learning and language. Mainstream researchers are now competing with philosophers, computer scientists, psychiatrists and physicists in the quest for the Holy Grail of consciousness. Not surprisingly, conferences are proliferating. In April last year, more than 300 investigators gathered at the University of Arizona Health Sciences Center in Tucson for a meeting titled 'Toward a Scientific Basis of Consciousness'. In November the same year, the Society for Neuroscience, the field's largest and most prestigious organisation, hosted its first symposium on consciousness in Miami.
These meetings have in turn spawned a number of books on theories of consciousness. In the last 4-5 years, no fewer than a dozen books on consciousness have been published. Likewise, new journals have sprung up to feed the burgeoning interest in this field, including Psyche, an e-mail journal based in Australia, and the Journal of Consciousness Studies, a British quarterly launched last summer. In fact, this decade is being observed as the Decade of the Brain in the US.
The consciousness bandwagon began rolling in 1990, when Francis Crick, now at the San Diego-based Salk Institute of Biology and Christof Koch, a neuroscientist at the California Institute of Technology, proclaimed that science was ready to launch an attack on consciousness. They contested the belief of many of their colleagues that consciousness cannot be defined, let alone studied. "Consciousness," they argued, "is really synonymous with awareness, and all forms of awareness--whether involving objects in the external world or highly abstract, internal concepts--seem to involve the same underlying mechanism, one that combines attention with short term memory."
Crick and Koch argued that to get an insight into consciousness, one would have to get inside the brain. Only by examining neurons and the interactions between them could scientists accumulate the kind of empirical, unambiguous knowledge that is required to create a truly scientific model of consciousness, one analogous to those that explain transmission of genetic information by means of DNA.
The two mavericks urged researchers to focus on visual awareness, since the visual system has already been well mapped in both animals and humans. They believe that by unravelling the neural underpinnings of the sense of sight, they might get a chance to see what lies behind more complex and subtle phenomena such as self-awareness, which may be unique to humans. "We may even comprehend why we have the paradoxical sensation of free will, an ineradicable sense that our minds exist independently of, and exert control over, our bodies," claims Crick in the Astonishing Hypothesis, a book published last year.
"The phenomenon of attention involves more than simple information processing", says Koch. "Consider, for example, the pattern that can be viewed either as a vase or as a pair of human profiles facing each other." Although the visual stimuli to the brain remains constant, the pattern that one is aware of, or attends to, keeps changing. The question is, what neural choreography corresponds to the change in attention?
The problem is that there is no mental equivalent of a celluloid screen where everything comes together in forming a perception. Even a single scene is processed by different neurons in different parts of the brain. But then what are those strokes and flourishes of the neural baton that organise the bewildering repertoire of images into a cortical symphony? This is known as the binding problem, considered by many neuroscientists to be the central issue of their field.
I think, therefore I am -- Or do I just think I am?
A growing band of mind-diggers say the answer to the binding problem must lie in some form of timing. An image may be reconstructed from all cells that are firing in a particular rhythm at a particular instant. Experiments have demonstrated that precise timing codes are the brain's primary organising principle, at least at the level of individual neurons, among specialised groups of neurons and across different parts of the brain. The basic idea is that cells involved in creating an image will fire simultaneously, thus binding together in time rather than space. Researchers recording the electrical activity of brain cells are coming up with evidence that cells fire in synchrony. The trouble is, nobody knows if such synchrony is related to behaviour. Neuroscientist Gyorgy Buzsaki, at Rutgers University, has found that a class of cells called inhibitory interneurons have a tendency to fire in a wavelike pattern. From the way they are distributed in the brain, these neurons could perform a binding function, he says.
While neuroscientists hunt for the 'neural glue', Gerald M Edelman of the Scripps Research Institute claims he has 'solved' the mystery of consciousness. He contends that our sense of awareness is merely the upshot of a Darwinian competition amongst neurons to create an effective cartographic representation of the world. Edelman, who shared the 1972 Nobel Prize for Medicine and Physiology for research on antibodies, has advertised this theory in a series of books--most recently, Bright Air, Brilliant Fire, published in 1992. Crick, however, has accused Edelman of offering unoriginal ideas clothed in gobbledygook.
But Crick himself is not immune to criticism. Tomaso Poggio of the Massachusetts Institute of Technology (MIT), a well-known authority on perception, thinks the connectionists--those seeking the key to consciousness in the neural labyrinth--may overemphasise mechanisms that might coordinate, or bind together, the firings of neurons responding to sensory images. They may even overlook the role that the brain's plasticity, or ability to change its circuitry, might play in conjuring consciousness and other aspects of mind, argues Poggio.
Another neuroscientist, Antonio R Damasio of the University of Iowa, who maps mental faculties by studying brain-impaired patients, believes that because consciousness is moulded by an individual's interactions with the environment and with other people, a neural model of consciousness will probably have to be supplemented by cognitive and social theories.
As neuroscientists debate these issues among themselves, others have questioned whether conventional neuroscience--despite its success in unearthing important insights into various facets of the mind--can ever explain consciousness. These mavericks hail primarily from traditions outside mainstream neuroscience, such as physics and philosophy.
Mainstream researchers often accuse of them being less interested in clarifying consciousness than in mystifying it. For that reason, Owen Flanagan, a philosopher at the Duke University, has dubbed these sceptics "the new mysterians" (after the 1960s rock group Question Mark and the Mysterians, who performed the hit song 96 years).
The mind glue
One camp of mysterians proposes that the mysteries of the mind must be linked related to the mysteries of quantum mechanics--the physics that describes the behaviour of subatomic world. Their speculations rest on the principle that the act of measurement--which ultimately involves a conscious observer--influences the outcome of quantum events. Such notions have become more prominent lately because of Roger Penrose, the reigning high priest of quantum consciousness and a physicist at the University of Oxford.
Penrose's argument takes wings from the famous Godel's theorem. Authored by the Czech mathematician Kurt Godel, the 60-year-old mathematical demonstration states that any moderately complex system of axioms yields statements that are self-evidently true but cannot be proved with those axioms. Says Penrose, "The theorem implies that no deterministic, rule-based system--that is neither classical physics, computer science or neuroscience--can account for the mind's creative powers and ability to ascertain truth."
In the bizarre, anti-commonsense world of the quantum, things appear to have a multitude of identities-- describable only as a set of probabilities known as a wave function--until an act of measurement precipitates a definite outcome. It is as if the physical world wants to explore many alternative pathways before collapsing into a settled state. For the champions of quantum consciousness, this seems to be just what the creative human mind does: sample many paths and outcomes before the wave function collapses into the coherent state which is our logical stream of thought. But while the quantum theories of the mind sound attractive, they lack an experimental basis.
The neural connectionist hypothesis, by comparison, has a more firm basis. This idea sees the mind as the consequence of patterns of impulses dancing across the synaptic connections that make up the brain; a labyrinthine web of information rather than a special field or unknown force. What gives the connectionists confidence is that any interference with the functioning of the brain's 50 billion nerve cells--whether from strokes, drugs, the surgeon's scalpel or merely sleep--tends to alter subjective experience in a rather definite way. By contrast, there seems to be no way that quantum effects could play any part in brain activity.
John J Taylor, a physicist at King's College, London, and a supporter of the connectionist hypothesis, criticises Penrose for making light of quantum mechanics. For example, he says, spooky action--the instantaneous interaction between two bodies separated in space--and other quantum effects hijacked to explain consciousness are observed only at temperatures near absolute zero (-273.16 degree Celsius), or at any rate far below the ambient temperatures of the brain. Taylor says that in the hot sticky world of the brain, any evanescent quantum event pregnant with information would be drowned out in the hubbub of background thermal noise.
So the quantum theorists were desperately looking for plausible mechanisms through which quantum-level phenomena could have an effect on higher-level brain activity. In his latest book Shadows of the Mind, Roger Penrose argues the missing link could be cell structures called microtubules.
Microtubules are the lattice of protein rods that fill every cell in the body, creating an inner scaffolding or cytoskeleton. The exact role of these structures is still unknown to cell biologists. Yet, quantum theorists believe that microtubules might form the ultimate substrate for consciousness, although their actual theories vary wildly. These range from the idea that microtubules might generate a coherent electromagnetic field which structures the water trapped inside each protein cylinder, to the possibility that they might act as tiny optical computers inside each cell.
In fact, Penrose is convinced that the mind must exploit probabilistic effects that can be described only by quantum mechanics or "a new physical theory that will bridge quantum and classical mechanics and will go beyond computation." He even suggests that spooky action might be the solution to the binding problem.
The pessimists
Amongst the mysterians, there are philosophers of mind who believe that key to consciousness will never be revealed to us. Colin McGinn, a philosopher at Rutgers University, argued in his 1991 book The Problem of Consciousness, that because our brains are products of evolution, they have cognitive limitations. Just as rats or monkeys cannot even conceive of quantum mechanics, so we humans may be prohibited from understanding certain aspects of existence, such as the relation between mind and matter.
David Chalmers, an Australian at Washington University, claims that none of the physical theories addresses the most fundamental question about the mind: Why is the performance of these functions accompanied by subjective experience? After all, it isn't difficult to imagine a world of androids that resemble humans in every respect but have no conscious experience of the world. Chalmers maintains that philosophers can and must construct a higher-level theory to bridge the chasm between physical and subjective domains.
But Koch rubbishes Chalmer's idea. While admitting science may not be able to solve all the mysteries of the mind, he claims philosophy has a much slimmer chance of providing lasting insights about the mind-body problem or the question of free will. He adds that when considering such conundrums, philosophers should do well to listen to what their illustrious forebear Ludwig Wittgenstein said once: "Whereof one doesn't know, thereof one mustn't speak."
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