What would happen if we were to try to transplant a piece of brain from one person into another?

Chris - Well actually, scientists have done this in a number of ways. In one instance, there was a complete head transplant done on a chimpanzee where the brain and head from one animal was grafted onto the blood vessels of another, recipient, body.

Now that's all well and good in the sense that it keeps the brain alive because the blood supply is preserved, but what it does involve is severing the connection between the brain and the spinal cord, which is how all the information gets into and out of the brain pretty much.

That means that the animal is destined to have no mobility and no ability to feel incoming information from the rest of its body. So, scientists, if they were going to do head transplants would have to surmount that one.

But, there are limited neuronal grafting and transplant studies being done because there are some neurological diseases, specifically neurodegenerative diseases, which are associated with the death or loss of certain subclasses or groups of nerve cells in the brain.

So scientists have reasoned that, if you're losing certain populations of cells in the brain, perhaps what we need to do is to put new cells back into that bit of the brain and perhaps they will wire in and they can do the job that these cells that have been lost used to do.

A good example of this is Parkinson's disease, because we know that one specific group of cells that make the chemical dopamine are lost from the brain in this disease.

Scientists have now done a number of experiments where they take foetal brain tissue - and you need foetal brain tissue because this seems to be critical because the cells seem to have a more robust phenotype - in other words, they seem to survive better - and if you harvest those cells that are destined to become dopamine-producing nerve cells in foetuses and you put those into the brain of an individual with Parkinson's disease, into the part of the brain that is lacking dopamine, in other words, is affected by the disease, the cells seem to have the ability to survive to a limited extent, and also, wire themselves in and produce dopamine to make up for the shortfall.

So, scientists are doing that with Parkinson's disease. They are also looking at the disease, Huntington's disease, which is another neurodegenerative disease but is caused by the loss of a different class of nerve cells. So they're trying similar tricks there.

It's early days, and the results have been mixed, but they do show promise and so we think that there is a good reason to be pursuing this.