Did you know that your brain has trillions of synapses? How do all those cells ever come to a consensus?!

[link|http://www.pbs.org/wgbh/nova/mind/electric.html|
Secrets of the Mind: The Electric Brain]

NOVA: How does consciousness come into this view of the brain? Is consciousness a mysterious phenomenon, in your opinion?

Llin\ufffds: I don't think so. I think consciousness is the sum of perceptions, which you must put together as a single event. I seriously believe that consciousness does not belong only to humans; it belongs to probably all forms of life that have a nervous system. The issue is the level of consciousness. Maybe in the very primitive animals, in which cells did not have a single systemic property -- in which each cell was a little island, if you wish -- there may not have been consciousness, just primitive sensation, or irritability, and primitive movement. But as soon as cells talked to one another there would be a consensus. This is basically what consciousness is about -- putting all this relevant stuff there is outside one's head inside, making an image with it, and deciding what to do. In order to make a decision you have to have a consensus.

NOVA: But it all just boils down to cells talking to one another?

Llin\ufffds: Some people believe we are something beyond neurons, but of course we are not. We are just the sum total of the activity of neurons. We assume that we have free will and that we make decisions, but we don't. Neurons do. We decide that this sum total driving us is a decision we have made for ourselves. But it is not.

NOVA: So this mass of wet gray tissue that is our brain is made up of neurons?

Llin\ufffds: The brain is made out of cells. It is a long and very distinguished group of cells -- about 550 million years or so old. These cells have a small mass. Our brain is about one-and-a-half liters, or three pounds, but it has 1010 cells, which is a huge number of cells. Ten billion cells. And each cell has 1,000 to 10,000 or so synapses -- the connections between the cells. So the brain has trillions of synapses.

NOVA: How does the brain keep all these different neurons communicating in synch?

Llin\ufffds: Neurons like one another very much. They respond to one another's messages, so they basically chat all day, like people do in society. "Where can I park?" "How much is it going to cost?" "Am I going to get a ticket?" One set of neurons talks to another set of neurons, and they talk back, so we have a dialogue between different components in the brain. And the dialogue is not between one cell and another cell, but rather between many cells and many other cells. It's like having a huge number of people holding hands, dancing together, making ever-changing circles and organized together in such a way that every cell belongs, at some time, to some circle. It's like a huge square dance. Each dancer belongs to a particular movement at a particular time.