xodarap replied 15 years ago (Dec 28th 2008, 11:31:52 am)
Thank you Robert Ettinger for that reasonable listing of what qualia are _not_. I like it.
My proposed solution fulfils pretty much all of the criteria but pushes the envelope inwards a bit in one or two places. I'm hoping we can isolate the discrepant bits and nut out why Robert asserts a couple of things which might "kibosh" his quest unless we tweak the terminology or definitions a bit.
* My proposal is that human brains spontaneously generate, and then cause to evolve, dynamic logical structures which are made of transiently self-sustaining swarms or clouds of neuronal surface impulses [depolarisations]. For any such cloud or swarm the neurons in question sustain the pattern of impulse pathways until the pattern is suppressed by other such swarms or it mutates into one or more different, consequential, swarms.
This idea is not new and other people have named this sort of thing "cell assembly", "repertoire", "singularity", and so forth. The key underlying concept is that the figurative nature or meaning of the thing is embodied in the locations of the neuron members of the interacting assembly and also in the temporal features of the "mass action" manifested by the vast numbers of impulses.
There are significant reasons for believing that the mass-action features of cell assemblies are crucial. Steve Lehar explains some of these on his website:
[other links to be had from wikipedia:
The simplest inference about mass-action features is that such cell assemblies involve some feedback loops and what Gerald Edelman calls re-entrant signalling. The outcome of these is that the swarms of impulses rapidly fall into large scale wave patterns which constrain the spatia-temporal structure of the self-sustaining cloud.
My rather simple minded way of explaining how this must work is by analogy with the problem of "water hammer" that occurs often in domestic water systems. What happens in water hammer is that some features of a particular piping arrangement, in particular a length of straight-ish piping leading to a tap [faucet for USA] and a loose washer/jumper in that tap, cause the washer to start oscillating as the tap is opened so that the flow of water is repeatedly stopped and started as the washer/jumper bounces up and down on the valve seat; I suspect also that a trapped air bubble is often involved but maybe it is just a consequence of the limited compressibility of the water itself. Note that the energy driving the hammer phenomenon comes from the pressure of the mains supply.
How this applies to cell assemblies is that neuron membrane depolarisations are not simply a tiny current of charge across the membrane which propagates in a kind of domino effect, there is also a minuscule movement of mass which constitutes a pressure/temperature wave along the bi-lipid cell membrane. The energy diving this system of course comes from the supply to the ion pumps which move the sodium and potassium ions back across thus resetting the membrane for its next impulse. My contention is that there is a feedback to individual neurons from the mass of other neurons around - and possibly via glial cells also at longer time scales - which is mediated by or a consequence of longer range electrical and kinetic/phonic effects.
* The net result is that any activated neuronal cell assembly should fall into a dynamic logical structure that is capable of influencing the brain in a potentially significant way. This can be by excluding other cell assemblies from activating or by provoking different assemblies into existence.
That such dynamic logical structures can and usually do represent things other than themselves can wait for my next post.