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What is the nature of consciousness? Is it limited to humans? Does

free will exist? Read on for one scientist's view.

The Electric BrainHow does a three-pound mass of wet gray tissue (the

brain) succeed in representing the external world so beautifully? In

this interview with noted neuroscientist Rodolfo Llinás of the New

York University School of Medicine, find out how the rhythm of

electrical oscillations in the brain gives rise to consciousness, and

how failures in this rhythm can lead to a variety of brain disorders.

NOVA: Let's start by talking about why one needs a nervous system --

or a brain -- in the first place.Llinás: That's a very intriguing

issue. The nervous system is about 550 million years old, and it

first came about when cells decided to make animals. Basically there

are two types of animals: animals, and animals that have no brains;

they are called plants. They don't need a nervous system because they

don't move actively, they don't pull up their roots and run in a

forest fire! Anything that moves actively requires a nervous system;

otherwise it would come to a quick death. NOVA: Why would it die if

it didn't have a nervous system?Llinás: Because if you move, the

variety of environments that you find is very large. So if you happen

to be a plant you have to worry only about the very small space you

grow into. You don't have to do anything other than maybe move up and

down. And you're following the sun anyhow, so there is no planned

movement, and therefore there is no necessity to predict what is

going to happen if, which is what the nervous system seems to be

about. It seems to be about moving in a more or less intelligent way.

The more elaborate the system, the more intelligent the movement.

NOVA: So you need a nervous system in order to be able to predict the

future? Llinás: Yes, and in order to predict you have to have, at the

very least, a simple image inside that tells you something about the

purpose of the outside world. That is common to all nervous systems

of all forms that we know of. Each animal has a different universe --

the universe it sees, the universe it feels, the universe it tastes.

Earth probably looks very different not only for all of us as

individual humans, but also for different animals. NOVA: How does

consciousness come into this view of the brain? Is consciousness a

mysterious phenomenon, in your opinion?

"We assume we have free will, but we don't."

Llinás: 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.

This colored scanning electron micrograph shows the synapses, or

connections, between two nerve fibers (in purple) and a nerve cell

(yellow). The picture is magnified 10,000 times.

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

another?Llinás: 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?Llinás: 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?

"Neurons like one another very much. They basically chat all day."

Llinás: 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. NOVA: And there's music that keeps them all dancing

together?Llinás: Right. It's generated by the neurons themselves.

Neurons have an intrinsic rhythm, a bit like a hum. They generate

this electrical dance at a given frequency because they have similar

rhythms -- they hum in unison. But as in the case of choirs and

dancing, you can have two groups doing different things at the same

time.

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