X-Message-Number: 8041 Date: Thu, 10 Apr 97 21:55:11 From: Mike Perry <> Subject: Seat of Consciousness In an earlier post today, I made an effort at defining the "seat of consciousness." I said it was the minimal brain region, some part of which is always active when the subject is "conscious." But this definition has problems, and won't always work. For example, suppose the whole brain is needed for consciousness, i.e. every neuron must be active or you have no consciousness. Then every cell could qualify as a "seat of consciousness" as I've defined it--there would be no single seat of consciousness. In practice we might aim at an "operational" definition. If, using PET scans, etc. we find that some part of the brain is always active when consciousness is present, is sufficient by itself for consciousness, and no other part of the brain meets either of these two requirements, we could identify that part as the seat of consciousness. But it's also interesting to pursue the more theoretical problem a little further. (This perhaps would offer additional insight into both natural and artificial systems that might qualify as "conscious" to some degree.) So I propose the following. First, say we call a part of the brain that is required for consciousness a primary region. This means that if this part is shut down completely, there is no consciousness. So the whole brain in particular is one such region. (Here I'm assuming that consciousness--the consciousness of "the person who speaks" anyway, is resident somewhere in the brain. Another assumption is that the smallest functioning subunit of the brain is a cell, so that all regions brain are finite sets of cells.) It ought to be possible then to talk about a minimal primary region--a region of the brain as small as possible, that is required for consciousness. Of course, in the real, fuzzy world the applicability of this concept cannot be taken for granted either, but I'm assuming it here as a "first cut." Every primary region, then, must have at least one minimal, primary subregion, given that we can go all the way down to the level of individual cells as our subregions. I would then define the seat of consciousness as the union or sum of all the minimal primary regions. For example, let's assume that the whole brain had to be active to have consciousness--turn even one cell off and you lose it (very unrealistic, but useful for illustration). Then the minimal primary regions would consist of a single cell each, and their sum would be the whole brain as required. On the other hand, if the MTRF, fully active, were both necessary and sufficient for consciousness, then again the minimal primary regions would be single cells--in this case cells of the MTRF--and their sum would be the whole MTRF. If there are two, disjoint regions of the brain, each of which could independently support consciousness, but at least one had to be completely active, then the minimal primary regions would consist of a *pair* of cells, one cell chosen from each region. The seat of consciousness would then be the sum of the pairs, i.e. the sum of the two regions. Similarly, if there are n disjoint regions, such that turnon of one is both necessary and sufficient for consciousness, then the minimal primary regions would consist of (unordered) n-tuples of cells, each cell chosen from one of the n regions, and the sum of the n regions would again be the seat of consciousness. The above examples are vastly oversimplified from real life, of course, but will convey the general idea. I think this idea bears further investigation (or quite possibly it has been investigated). With a little more mathematical rigor, it might be made into a theory that would produce interesting theorems--then we would have to see how far the results might be relevant. Or perhaps there are still major flaws in this approach, that investigation could uncover and correct. Mike Perry http://www.alcor.org Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=8041