Around 1970, it was found that there were not only parts of the brain, but particular cells.
"Face cells" were discovered around 1970. And now we know that there are hundreds of other sorts of cells, which can be very, very specific.
So you may not only have "car" cells, you may have "Aston Martin" cells.
I saw an Aston Martin this morning. I had to bring it in. And now it's in there somewhere.
Now, at this level, in what's called the inferotemporal cortex, there are only visual images, or figments or fragments.
It's only at higher levels that the other senses join in and there are connections with memory and emotion.
And in the Charles Bonnet syndrome, you don't go to those higher levels.
You're in these levels of inferior visual cortex where you have thousands and tens of thousands and millions of images,
or figments, or fragmentary figments, all neurally encoded in particular cells or small clusters of cells.
Normally these are all part of the integrated stream of perception, or imagination, and one is not conscious of them.
It is only if one is visually impaired or blind that the process is interrupted.
And instead of getting normal perception, you're getting an anarchic, convulsive stimulation, or release, of all of these visual cells in the inferotemporal cortex.
So, suddenly you see a face. Suddenly you see a car. Suddenly this, and suddenly that.
The mind does its best to organize and to give some sort of coherence to this, but not terribly successfully.
When these were first described, it was thought that they could be interpreted like dreams.
But in fact people say, "I don't recognize the people. I can't form any associations."
"Kermit means nothing to me." You don't get anywhere thinking of them as dreams.
Well, I've more or less said what I wanted. I think I just want to recapitulate and say this is common.
Think of the number of blind people. There must be hundreds of thousands of blind people who have these hallucinations, but are too scared to mention them.
So this sort of thing needs to be brought into notice, for patients, for doctors, for the public.
Finally, I think they are infinitely interesting and valuable, for giving one some insight as to how the brain works.