WEBVTT

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We see with the eyes,

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but we see with the brain as well.

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And seeing with the brain
is often called imagination.

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And we are familiar with the landscapes
of our own imagination,

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our inscapes.

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We've lived with them all our lives.

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But there are also hallucinations as well.

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And hallucinations
are completely different.

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They don't seem to be of our creation.

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They don't seem to be under control.

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They seem to come from the outside
and to mimic perception.

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So I am going to be talking
about hallucinations

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and a particular sort
of visual hallucination,

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which I see among my patients.

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A few months ago, I got a phone call
from a nursing home where I work.

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They told me that one of their residents,
an old lady in her 90s,

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was seeing things,

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and they wondered if she'd gone bonkers

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or, because she was an old lady,

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whether she'd had a stroke,
or whether she had Alzheimer's.

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And so they asked me
if I would come and see Rosalie,

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the old lady.

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I went in to see her.

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It was evident straightaway
that she was perfectly sane

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and lucid and of good intelligence,

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but she'd been very startled
and very bewildered,

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because she'd been seeing things.

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And she told me --
the nurses hadn't mentioned this --

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that she was blind,

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that she had been completely blind
from macular degeneration for five years.

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But now, for the last few days,
she'd been seeing things.

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So I said, "What sort of things?"

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And she said, "People in Eastern dress,

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in drapes, walking up and down stairs.

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A man who turns towards me and smiles,

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but he has huge teeth
on one side of his mouth.

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Animals too.

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I see a white building.
It's snowing, a soft snow.

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I see this horse with a harness,
dragging the snow away.

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Then, one night, the scene changes.

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I see cats and dogs walking towards me.

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They come to a certain point
and then stop.

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Then it changes again.

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I see a lot of children.
They're walking up and down stairs.

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They wear bright colors, rose and blue,

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like Eastern dress."

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Sometimes, she said,
before the people come on,

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she may hallucinate
pink and blue squares on the floor,

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which seem to go up to the ceiling.

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I said, "Is this like a dream?"

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And she said, "No, it's not
like a dream. It's like a movie."

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She said, "It's got color.
It's got motion.

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But it's completely silent,
like a silent movie."

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And she said it's a rather boring movie.

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(Laughter)

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She said, "All these people
with Eastern dress,

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walking up and down,
very repetitive, very limited."

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(Laughter)

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And she had a sense of humor.

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She knew it was a hallucination,
but she was frightened.

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She had lived 95 years,

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and she'd never had
a hallucination before.

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She said that the hallucinations were
unrelated to anything she was thinking

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or feeling or doing,

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that they seemed to come on
by themselves, or disappear.

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She had no control over them.

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She said she didn't recognize
any of the people or places

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in the hallucinations,

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and none of the people or the animals --

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well, they all seemed oblivious of her.

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And she didn't know what was going on.

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She wondered if she was going mad
or losing her mind.

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Well, I examined her carefully.

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She was a bright old lady,

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perfectly sane.

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She had no medical problems.

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She wasn't on any medications
which could produce hallucinations.

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But she was blind.

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And I then said to her,
"I think I know what you have."

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I said, "There is a special form
of visual hallucination

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which may go with deteriorating
vision or blindness.

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This was originally described," I said,

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"right back in the 18th century,

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by a man called Charles Bonnet.

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And you have Charles Bonnet syndrome.

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There's nothing wrong with your brain.
There's nothing wrong with your mind.

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You have Charles Bonnet syndrome."

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And she was very relieved at this,

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that there was nothing
seriously the matter,

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and also rather curious.

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She said, "Who is this Charles Bonnet?"

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She said, "Did he have them himself?"

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And she said, "Tell all the nurses
that I have Charles Bonnet syndrome."

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(Laughter)

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"I'm not crazy. I'm not demented.
I have Charles Bonnet syndrome."

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Well, so, I did tell the nurses.

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Now this, for me, is a common situation.

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I work in old-age homes, largely.

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I see a lot of elderly people

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who are hearing-impaired
or visually impaired.

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About 10 percent
of the hearing-impaired people

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get musical hallucinations.

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And about 10 percent
of the visually impaired people

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get visual hallucinations.

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You don't have to be completely blind,

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only sufficiently impaired.

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Now, with the original description
in the 18th century,

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Charles Bonnet did not have them.

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His grandfather had these hallucinations.

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His grandfather was
a magistrate, an elderly man.

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He'd had cataract surgery.

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His vision was pretty poor.

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And in 1759, he described to his grandson

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various things he was seeing.

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The first thing he said
was he saw a handkerchief in midair.

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It was a large blue handkerchief
with four orange circles.

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And he knew it was a hallucination.

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You don't have handkerchiefs in midair.

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And then he saw a big wheel in midair.

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But sometimes he wasn't sure
whether he was hallucinating or not,

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because the hallucinations would fit
in the context of the visions.

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So on one occasion, when
his granddaughters were visiting them,

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he said, "And who are these
handsome young men with you?"

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(Laughter)

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And they said, "Alas, Grandpapa,
there are no handsome young men."

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And then the handsome
young men disappeared.

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It's typical of these hallucinations

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that they may come in a flash
and disappear in a flash.

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They don't usually fade in and out.

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They are rather sudden,
and they change suddenly.

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Charles Lullin, the grandfather,

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saw hundreds of different figures,

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different landscapes of all sorts.

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On one occasion, he saw a man
in a bathrobe smoking a pipe,

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and realized it was himself.

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That was the only figure he recognized.

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On one occasion, when he was walking
in the streets of Paris,

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he saw -- this was real -- a scaffolding.

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But when he got back home,
he saw a miniature of the scaffolding,

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six inches high,

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on his study table.

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This repetition of perception
is sometimes called "palinopsia."

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With him and with Rosalie,

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what seems to be going on --

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and Rosalie said, "What's going on?" --

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and I said that as you lose vision,

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as the visual parts of the brain
are no longer getting any input,

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they become hyperactive and excitable,

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and they start to fire spontaneously.

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And you start to see things.

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The things you see
can be very complicated indeed.

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With another patient of mine
who also had some vision,

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the visions she had could be disturbing.

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On one occasion, she said she saw
a man in a striped shirt in a restaurant.

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And he turned round,

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and then he divided
into six figures in striped shirts,

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who started walking towards her.

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And then the six figures came
together, like a concertina.

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Once, when she was driving,

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or rather, her husband was driving,

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the road divided into four

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and she felt herself going
simultaneously up four roads.

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She had very mobile
hallucinations as well.

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A lot of them had to do with a car.

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Sometimes she would see a teenage boy
sitting on the hood of the car.

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He was very tenacious,

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and he moved rather gracefully
when the car turned.

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And then when they came to a stop,

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the boy would do a sudden vertical
takeoff, 100 foot in the air,

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and then disappear.

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Another patient of mine
had a different sort of hallucination.

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This was a woman
who didn't have trouble with her eyes

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but the visual parts of her brain,

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a little tumor in the occipital cortex.

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And, above all, she would see cartoons.

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And these cartoons would be transparent,

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and would cover half
the visual field, like a screen.

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And especially, she saw
cartoons of Kermit the Frog.

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(Laughter)

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Now, I don't watch Sesame Street,

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but she made a point of saying,

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"Why Kermit?" she said,
"Kermit the Frog means nothing to me."

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You know, I was wondering about
Freudian determinants: Why Kermit?

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"Kermit the Frog means nothing to me."

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She didn't mind the cartoons too much.

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But what did disturb her

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was she got very persistent images
or hallucinations of faces,

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and as with Rosalie,
the faces were often deformed,

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with very large teeth or very large eyes.

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And these frightened her.

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Well, what is going on with these people?

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As a physician, I have to try
and define what's going on

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and to reassure people,

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especially to reassure them
that they're not going insane.

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Something like 10 percent, as I said,

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of visually impaired people get these.

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But no more than one percent
of the people acknowledge them,

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because they are afraid
they will be seen as insane or something.

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And if they do mention them
to their own doctors,

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they may be misdiagnosed.

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In particular, the notion
is that if you see things or hear things,

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you're going mad.

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But the psychotic hallucinations
are quite different.

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Psychotic hallucinations,
whether they are visual or vocal,

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they address you.

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They accuse you, they seduce you,
they humiliate you, they jeer at you.

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You interact with them.

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There is none of this quality
of being addressed

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with these Charles Bonnet hallucinations.

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There is a film. You're seeing a film
which has nothing to do with you --

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or that's how people think about it.

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There is also a rare thing
called temporal lobe epilepsy,

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and sometimes, if one has this,

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one may feel oneself transported
back to a time and place in the past.

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You're at a particular road junction.

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You smell chestnuts roasting.

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You hear the traffic.
All the senses are involved.

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And you're waiting for your girl.

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And it's that Tuesday
evening back in 1982.

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The temporal lobe hallucinations
are all sense hallucinations,

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full of feeling, full of familiarity,

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located in space and time,

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coherent, dramatic.

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The Charles Bonnet
ones are quite different.

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In the Charles Bonnet hallucinations,
you have all sorts of levels,

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from the geometrical hallucinations --

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the pink and blue squares the woman had --

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up to quite elaborate hallucinations

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with figures and especially faces.

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Faces, and sometimes deformed faces,

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are the single commonest thing
in these hallucinations.

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And one of the second
commonest is cartoons.

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So, what is going on?

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Fascinatingly, in the last few years,

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it's been possible to do
functional brain imagery,

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to do fMRI on people
as they are hallucinating,

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and, in fact, to find that different parts
of the visual brain are activated

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as they are hallucinating.

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When people have these simple,
geometrical hallucinations,

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the primary visual cortex is activated.

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This is the part of the brain
which perceives edges and patterns.

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You don't form images
with your primary visual cortex.

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When images are formed,

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a higher part of the visual cortex
is involved, in the temporal lobe.

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And in particular,
one area of the temporal lobe

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is called the fusiform gyrus.

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And it's known that if people
have damage in the fusiform gyrus,

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they may lose the ability
to recognize faces.

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But if there's an abnormal activity
in the fusiform gyrus,

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they may hallucinate faces,

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and this is exactly what you find
in some of these people.

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There is an area
in the anterior part of this gyrus

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where teeth and eyes are represented,

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and that part of the gyrus is activated

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when people get
the deformed hallucinations.

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There is another part of the brain
which is especially activated

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when one sees cartoons.

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It's activated
when one recognizes cartoons,

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when one draws cartoons
and when one hallucinates them.

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It's very interesting
that that should be specific.

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There are other parts of the brain
which are specifically involved

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with the recognition and hallucination
of buildings and landscapes.

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Around 1970, it was found that there were
not only parts of the brain,

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but particular cells.

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"Face cells" were discovered around 1970.

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And now we know that there are
hundreds of other sorts of cells,

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which can be very, very specific.

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So you may not only have "car" cells,
you may have "Aston Martin" cells.

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(Laughter)

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I saw an Aston Martin this morning.
I had to bring it in.

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(Laughter)

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And now it's in there, somewhere.

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So --

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(Laughter)

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now, at this level, in what's called
the inferotemporal cortex,

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there are only visual images,

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or figments or fragments.

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It's only at higher levels
that the other senses join in

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and there are connections
with memory and emotion.

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And in the Charles Bonnet syndrome,

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you don't go to those higher levels.

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You're in these levels
of inferior visual cortex,

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where you have thousands
and tens of thousands

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and millions of images,

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or figments or fragmentary figments,

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all neurally encoded in particular cells
or small clusters of cells.

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Normally, these are all part
of the integrated stream of perception,

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or imagination,

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and one is not conscious of them.

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It is only if one
is visually impaired or blind

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that the process is interrupted.

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And instead of getting normal perception,

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you're getting an anarchic,

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convulsive stimulation, or release,

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of all of these visual cells
in the inferotemporal cortex.

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So, suddenly, you see a face.
Suddenly, you see a car.

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Suddenly this and suddenly that.

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The mind does its best to organize

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and to give some sort
of coherence to this,

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but not terribly successfully.

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When these were first described,

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it was thought that they could be
interpreted like dreams.

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But, in fact, people say,

00:15:59.840 --> 00:16:04.252
"I don't recognize the people.
I can't form any associations.

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Kermit means nothing to me."

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You don't get anywhere,
thinking of them as dreams.

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Well, I've more or less
said what I wanted.

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I think I just want to recapitulate
and say this is common.

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Think of the number of blind people.

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There must be hundreds
of thousands of blind people

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who have these hallucinations

00:16:27.344 --> 00:16:29.465
but are too scared to mention them.

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So this sort of thing
needs to be brought into notice,

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for patients, for doctors, for the public.

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Finally, I think they are
infinitely interesting and valuable,

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for giving one some insight
as to how the brain works.

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Charles Bonnet said, 250 years ago --

00:16:50.782 --> 00:16:54.226
he wondered how,
thinking of these hallucinations,

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how, as he put it, the theater of the mind

00:16:56.954 --> 00:17:00.304
could be generated
by the machinery of the brain.

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Now, 250 years later,

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I think we're beginning
to glimpse how this is done.

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Thanks very much.

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(Applause)

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Chris Anderson: That was superb.
Thank you so much.

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You speak about these things
with so much insight

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and empathy for your patients.

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Have you yourself experienced
any of the syndromes you write about?

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Oliver Sacks: I was afraid
you would ask that.

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(Laughter)

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Well, yeah, a lot of them.

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And, actually, I'm a little
visually impaired myself.

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I'm blind in one eye
and not terribly good in the other.

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And I see the geometrical hallucinations.

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But they stop there.

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CA: And they don't disturb you?

00:17:43.738 --> 00:17:46.977
Because you understand what's doing it,
it doesn't make you worried?

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OS: Well, they don't disturb me
any more than my tinnitus,

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which I ignore.

00:17:53.379 --> 00:17:55.067
They occasionally interest me,

00:17:55.091 --> 00:17:58.000
and I have many pictures
of them in my notebooks.

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I've gone and had an fMRI myself,

00:18:00.900 --> 00:18:03.955
to see how my visual cortex
is ticking over.

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And when I see all these hexagons

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and complex things, which I also have,

00:18:10.250 --> 00:18:12.013
in visual migraine,

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I wonder whether everyone
sees things like this

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and whether things
like cave art or ornamental art

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may have been derived from them a bit.

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CA: That was an utterly,
utterly fascinating talk.

00:18:22.505 --> 00:18:24.317
Thank you so much for sharing.

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OS: Thank you. Thank you.

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(Applause)