From an article in the latest New Scientist, by Susan Greenfield, Professor of Pharmacology at Oxford
A justification for a marxist, and also, to be provocative, a post modernist theory of consciousness: Chris Burford London ...... The best way to begin to explain consciousness is to draw up a shopping list of the features or properties we expect. Then neuroscientists can go back to their labs and see how the brain could deliver. First, I don't believe we should be looking for one special brain region. Many regions are active while you are awake, but as you become unconscious, they all shut down in a fairly uniform way. When someone has been anaesthetised, there's no one region that lights up or gets extinguished. There is no single specialised "centre for consciousness". Secondly, although consciousness comes from more than one brain area, at any one moment you have only one consciousness. The world seems of a piece. So we can expand the first item on the list to say that while consciousness is distributed all over the brain, somehow the activities of the different regions are coordinated. And if there's no special centre or neurons for consciousness then the neurons and areas that generate it must do other jobs as well. The physical manifestation of consciousness must be something that happens in or to ordinary brain cells at certain times, but not others. Also on my shopping list is the notion that the more complex the brain the deeper the consciousness. The idea of degrees of consciousness helps answer questions such as when a fetus becomes conscious, and which other animals are conscious. I can't see a physical Rubicon when the brain of a developing fetus changes suddenly, nor any obvious cut-off in the animal kingdom between a nervous system that generates consciousness and one that does not. We should think instead of a continuum: a rat is conscious but not as conscious as a dog; a dog is conscious but not as conscious as a primate; and so on. Even an ant will have a tiny modicum of consciousness. If you think of consciousness like this-as something that varies by degree-there are two interesting consequences. The first is that we may be more conscious at some times than at others, hence our experience of states of "heightened awareness", and the conviction that we can "raise" or "deepen" our consciousness. The second, crucial consequence is that we will have finally converted consciousness from a qualitative to a quantitative phenomenon. We can then look for a measure of the depth of our consciousness as it varies from one moment to the next, and search the brain for something that contracts or expands with it. I think that the most logical place to look is in very large networks-"assemblies"-of brain cells. You're born with pretty much all the brain cells you'll ever have, but as you mature these cells develop more interconnecting branches. Our brains are incredibly plastic, and these connections grow and change with every experience. Babies evaluate the world in purely sensory terms-how sweet, how fast, how cold, how loud. But gradually these abstract sensations coalesce into people and objects with meaning and associations. It's these personal connections and associations that I think of as the "mind". The mind is your personalised brain, which allows you to see the world in terms of what you have experienced already. Even if you're a clone-that is, an identical twin-your mind will be unique. You see the world in terms of things that have happened to you alone. If we see a familiar person, our visual system activates a "hub" of brain cells that corresponds not only to the shapes, movements and colours of a face, but to all the associations set up in our mind by our experiences of that person. That can all happen without our being aware of it. Consciousness, I believe, is generated as this active, hard-wired hub corrals huge numbers of other brain cells around it to form a vast working assembly that lasts for just a trice. The image I have is like throwing a stone into a puddle, producing ripples of consciousness. We now know the brain to be capable of forming such highly transient assemblies. Amiram Grinvald at the Weizmann Institute in Rehovot, Israel, has shown that in response to a flash of light, as many as 10 million brain cells become active together, coordinated into a working assembly that lasts for less than a quarter of a second-exactly the space and time scales I think we should be exploring. The assembly will be slightly different every time. Partly it will depend upon the size and strength of the stimulation of the hub, but also on the levels of a variety of chemical messengers-neurotransmitters-which change moment by moment. These transmitters "modulate" the activity of large groups of cells and mediate arousal levels, your sleep-wake cycle and your dreaming. In physiological terms, these put cells on "red alert"-they can predispose brain cells to be recruited into the working assembly, triggering lots of covert associations. I think it is the activity of these transient neuronal assemblies that correlates with the depth of your consciousness at any one moment...... _______________________________________________ Marxism-Thaxis mailing list [EMAIL PROTECTED] To change your options or unsubscribe go to: http://lists.econ.utah.edu/mailman/listinfo/marxism-thaxis
