Article by Boris's sister, Rachel Johnson, about their mother's decision to donate her brain for research. A very intelligent decision When her mother, who has Parkinson's disease, said that she wanted to donate her brain for research into the illness, Rachel Johnson decided to find out exactly what would happen to it '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 Institute of Neurology at University College, London, and into a lift taking us to the Queen Square Brain Bank. Prof Revesz shows a part of his research to Rachel, her brother Boris and their mother, Charlotte For further information, contact Susan Stoneham on 020 7837 8370, e-mail or log on to website. 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. Everything was ready. A selection of gleaming, razor- sharp knives lay on a folded cloth. Within seconds, the seat of consciousness of this woman, the repository of her every emotion, thought, instinct and reflex for more than eight decades, was about to be eviscerated. All that had animated and driven her from birth to death was located there, in just 1,200g of dense, enfolded tissue. Prof Revesz placed the pale, veal-coloured organ with what looked like bluish-purple veins worming across its dimpled walnut surface, on to a sort of chopping board, picked up a scalpel and cut it in half. Suddenly, it seemed improbable that such a small amount of matter could be so vital or be responsible for so much. 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. "I might sit down, actually," said our mother, Charlotte Johnson Wahl. I wasn't surprised by her reaction. After all, many years hence - I hope - the brain on the slab will be hers. Everyone is aware - or should be - of the importance of organ donation. It's easy to register, at any age, to give all or any of these organs: heart, lungs, kidney, pancreas, liver, and small bowel. It is also possible to donate corneas, skin, bone and heart valves. Still, only 22 per cent of the population has registered and almost 7,000 people were still waiting for transplants that would save their lives or at the very least transform them. But what's that got to do with brains, you ask? While it is true that brain and brain tissue transplants are not yet a practical reality (although foetal brain tissue can be transplanted into an adult brain), the donation of this organ is, arguably, just as important. 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. She is 64 and has had Parkinson's disease for more than 15 years. The disease is well-controlled with drugs and she continues to work as an artist. For her, the most problematic symptom is ''freezing'' - difficulty in initiating a movement. 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. "Would you like to see the Brain Bank now?" asked Prof Lees, who is my mother's consultant neurologist. So we left the Brain Cut Room, and another door was unlocked for us. "The brains are removed after death, then they are divided up," explained Karen Shaw, the autopsy nurse, who liaises with donors and families. It was she who first raised the possibility of brain donation with my mother, resulting in our visit. "One half of the brain is 'fixed', that means it is placed in formalin for two months,'' she said. ''Then the formalin-fixed hemisphere - the bit used for making a diagnosis - is sliced into half-centimetre slices and stored." We peered inside a room that was crammed with floor-to-ceiling shelves holding numbered Tupperware containers of chopped and pickled brains. "The other hemisphere of the brain is also sliced, then flash-frozen and stored," Shaw continued, as the thought crossed my mind that it was good housekeeping to keep half in the larder, and half in the deep freeze. The rest of the visit was spent discussing whether or not there is any correlation between brain size and intellect (answer - no). We spoke of Einstein - whose brain was pilfered by an American pathologist and kept in a library in a jar for years - and also of Anatole France, the Nobel prizewinning novelist whose brain weighed a mere 1,017g (a man's brain usually weighs around 1,300g). Although the experience was not without its macabre moments, our visit reassured us that our mother was doing the right thing. But what about the would-be donor herself? What was her reaction, after seeing the cutting room, the larder, the deep freeze? "It did make me think about death," she admitted afterwards. "Apart from that, I had no qualms at all. I think that donating your brain is an excellent thing to do. But I did have some qualms on my children's account." 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.