Cross-posted from New Savanna. 

About a year ago I uploaded a post with a typically ungainly title, The structured physical system hypothesis (SPSH), Polyviscous connectivity [The brain as a physical system]. It’s that word, “polyviscous,” that’s got my present attention. Since then I’ve done a number of posts using that idea, whatever it is. This is another of those ideas.

So, viscosity. Honey is more viscous than, say, water. It flows more slowly, much more. What happens if you drop a lump of honey into a tumbler of water? It sinks to the bottom in a continuous lump and flattens out along the bottom. It will begin to diffuse into the water along the boundary, but I don’t know how long, if ever, it will take to mix completely. Now, put a stick down into the tumbler until it extends into the honey. Give is a stir or three, but no more. Now you’ll have gobs and threads of honey mixed in with water in a complex and somewhat irregular and ragged way. That’s a simple polyviscous fluid. It has regions of relatively high viscosity and other regions of relatively low viscosity. Now imagine a fluid with 5, 10, 27, 48, and more different levels of viscosity, from all but solid like cold tar through the wispiest whatever. Polyviscosity.

As the title of the year-old post indicates, I was thinking in terms of connectivity:

Thus I say that the cortical network as a whole exhibits polyviscous connectivity. What do I mean? Some connections are highly resistant to change, and thus have high viscosity. Others change quite readily, and have low viscosity.

OK. Now let’s shift our thinking just a bit and think of the mind as a polyviscous fluid. The mind, as the saying goes, is what the brain does. And that is very complex.

Imagine that you’re watching a movie, make it a Hong Kong martial arts movie. Your mind is entrained to the images on the screen. During a fight scene the level of mental viscosity is relatively how. The fight is over and the hero rests, contemplating the sunset, let’s say. The viscosity is somewhat higher.

Yet, while you’re entrained by the film, you’re not completely absorbed into. While the hero contemplates the sunset, you take a bit of popcorn. And maybe you were munching furiously during the fight. So, even as you were watching the film you slipped in some mental popcorn “frames” among the film frames. Very slippery, low viscosity.

When I wrote my book on music, Beethoven’s Anvil, I talked of the mind as neural weather. Thus (p. 72):

If the functional proclivities of a patch of neural tissue are not relevant for a current activity, those neurons will not be firing very often, but they will still generate some output. The only neuron that does not generate any output is a dead one. Neurons that are firing at low intensity one moment may well be recruited to more intense activity the next. As Walter Freeman has said, a low level of activity is still a means of participating in the evolving mental state.

The mind, in this view, is thus like the weather. The same environment can have very different kinds of weather. And while we find it natural to talk of weather systems as configurations of geography, temperature, humidity, air pressure etc., no overall mechanism regulates the weather. The weather is the result of many processes operating on different temporal and spatial scales.

At the global level and on a scale of millennia we have the long-term patterns governing the ebb and flow of glaciers which, in one commonly accepted theory, is a function of wobble and tilt in the earth’s spin axis and the shape of the earth’s orbit. At the global level and operating annually we have the succession of seasons, which is caused by the orientation of the earth with respect to the sun as it moves through the year. We can continue on, considering smaller and smaller scales until we consider the wind ripping through the twin towers of the World Trade Center or even the breeze coming in through your open window and blowing the papers off your desk.

Weather is regular enough that one can predict general patterns at scales of hours, days, and months, but not so regular that making such predictions is easy and routinely reliable. Above all, there is no central mechanism governing the weather. It just happens.

I develop that idea further in a couple of posts, The Mind is What the Brain Does, and Very Strange, and Neural Weather, an Informal Defense of Psychoanalytic Ideas.

So, neural weather, polyviscous fluid. Perhaps we’re getting somewhere. The mind IS what the brain does, and what the brain does is complex and varies along a wide range of time scales. The brain’s overall physical structure is relatively constant throughout life, barring injury and disease. But the connectivity changes over a variety of time scales from seconds through hours and days and even longer (think of cortical plasticity). There is much, perhaps most, millisecond to millisecond, activity that produces no synaptic change at all. A very fluid phenomenon, over multimer time scales.