Gerald M.Edelmann A UNIVERSE OF CONSCIOUSNESS Basic 2000

pg. 16 (vgl. Zitate Sherrington /Russell pg.10) WHAT NEEDS TO BE EXPLAINED The neuroscientist Charles Sherrington and the philosopher Bertrand Russell, in vividly illustrating the problem of consciousness, resorted to the same example: A pencil of light enters the eye, gives rise to a series of electrical and chemical steps, and finally produces effects at the top of the brain. But now, as Sherrington noted, ´there succeeds a change wholly inexplicable and unexpected": Each of us consciously sees the light. This seeing is something subjective, totally different from the objective physical processes that precede and accompany it. This, in a nutshell, is the special problem of consciousness­the world knot. Sometimes the best way to solve a problem is simply to ask the right question. And sometimes the best way to ask the right question is to come up with an example that makes most explicit what the problem is about. Let us follow Sherrington's and Russell's leads and consider a simple physical device, such as a photodiode, that can differentiate between light and dark and provide an audible output.  Let us then consider a conscious human being performing the same task and then giving a verbal report. The problem of consciousness can now be posed in elementary terms: Why should the simple differentiation between light and dark performed by the human being be associated with and, indeed, require conscious experience, while that performed by the photodiode presumably does not? Or consider a thermistor tbat can differentiate between hot and cold. Why should the thermistor remain a simple, dull physical device, incapable of generating any subjective or phenomenal quality, while when we perform the same function we become conscious of cold, of hot, and possibly even of pain? When considered in neural terms, this problem takes on an even more intriguing and paradoxical quality. Why should the activity of certain nerve cells, or neurons, in the brain correlate with the succession of private phenomenal states that we call conscious experience, while that of other neurons is deprived of such a remarkable property? For example, why is it that the activity of neurons in the retina that differentiate between light and dark is not directly associated with conscious experience, while that of certain neurons higher up in the visnal system apparently is? Or why is it that we are conscious of whether we are hot or cold, but we are not directly conscious of whether our blood pressure is high or low?  After all, there are intricate neural circuits that deal with the regulation of blood pressure just as there are neural circuits that deal with the regulation of body temperature. More generally, why would a mere location in the brain or the possession of a particular anatomical or biochemical feature make the activity of certain neurons so privileged that it suddenly imbues the possessor of that brain with the flavor of subjective experience, with those elusive properties that philosophers call qualia? This is the central problem of conscious experience. In the following chapters, we examine what kind of neural processes actually explain the fundamental properties of consciousness, rather than merely correlate with them.  Many neuroscientists have emphasized particular neural structures whose activity correlates with conscious experience. It is not surprising that different neuroscientists end up favoring different structures. As we shall see in a number of cases, it is likely that the workings of each structure may contribote to consciousness, but it is a mistake to expect that pinpointing particular locations in the brain or understanding intrinsic properties of particolar neurons will, in itself, explain why their activity does or does not contribute to conscious experience.  Such an expectation is a prime example of a category error, in the specific sense of ascribing to things properties they cannot have. We believe instead that what is crucial is to concentrate on the processes, not just the brain areas, that support consciousness and, more specifically, to focus on those neural processes that can actually account for the most fundamental properties of consciousness.

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