A very intelligent decision

Would you like to see the dissection now?" asked Professor Andrew Lees, his eyes lighting up in anticipation. He hustled us out of the seminar room in the smart new premises of the UCL Institute of Neurology, and into a lift taking us to the Queen Square Brain Bank.

Seconds later, we were putting on white coats and preparing to enter a door bearing the notice 'Brain Cut Room'. Inside, a second prof, Tamas Revesz, was tenderly cupping the brain of an 85-year-old woman who had died a few weeks before in his rubber-gloved hands. …

Then with a firm, confident downstroke, he sliced again, shearing off a sizeable chunk. The professor held up the segment for our inspection. It looked like a quarter slice of cauliflower, with florets blooming along the cross-section.

"Golly," I said.

"Crumbs," said my brother Boris. …

Without a good supply of donor brains to examine, research into neurological diseases is merely academic. The brain, in its carapace of bone, cannot be examined without risk and damage during life as it can be after death.

When Prof Revesz sliced through the section of the mid-brain known as the substantia nigra (Latin for ''black substance'') which is responsible for aspects of movement and attention, he could see immediately that the deceased had had Parkinson's disease. There was a lack of pigment in that part of the brain. It was not nigra at all. It was blanca - the result of predatory proteins attacking the nerve cells.

Looking at a section under the microscope later, he was able to tell us more. He could identify exactly what type of Parkinson's it was, a discovery that could enable the woman's family to have her neuropathological diagnosis either confirmed or amended. It could also determine if there was a genetic component to her illness so that, if necessary, the family could receive genetic counselling.

Without her brain, Prof Revesz could not have known any of this. And with a steady supply of brains to dissect, it is possible to deepen understanding not just of how one person died but of neurological disease in general.

This is why my mother has signed up to donate her brain to the Queen Square Brain Bank, one of the largest brain tissue resources for the study of Parkinson's, movement disorders and dementia, in the world. …

Normal, or apparently healthy or "control" brains, are also vital for this research. There are 1,140 brains held in the Brain Bank, but at the moment only 300 of those are control organs from undiseased donors. More are needed. …

Of course, I can see that when the moment comes, it will be hard for us to make the call that will result in her brain being removed within a day of death, at a time when we will all be mourning our most darling mother.

But it would be harder had we not actually seen the expertise and care of the staff of the Queen Square Brain Bank - and their invaluable and skilled work. Now, I too have promised my so-far-healthy organ to the bank; the decision was, though, I hesitate to say it, a no-brainer.

Rachel Johnson, 'The Telegraph'