Joan Bakewell: This could stir up some painful memories

It is summertime in the park. A young man is there, joshing and joking with his friends. His girlfriend is there too, wearing long floaty clothes and lots of beads. Someone is listening to a Bee Gees track on their new-fangled Walkman. It is somewhere in the late 1970s, he thinks, but he is not sure. It is a delicious memory of a happy time.

The memory has surfaced because of electrodes reaching deep into his brain and driven by a pacemaker inserted in his chest. He is in fact a 30st, 50-year-old man being treated for obesity in a Canadian hospital, and the memory is a by-product of his treatment. It could prove to be the latest and most significant development in brain surgery. Neurosurgeons in Ontario using the process known as deep brain stimulation have accidentally discovered that the hypothalamus, when stimulated by current, produces spontaneous memories of events long ago. The hypothalamus has not usually been identified as the seat of memory. The discovery could revolutionise the treatment of, among other things, Alzheimer's Disease. There is quiet excitement all round.

Medicine has been galloping forward in recent years with ways of prolonging life, promoting better lifestyles and generally seeing an ageing population live long enough to fall victim to illnesses that afflict only the very old. Dementia is merely the most dramatic and distressing. Medicine has found ways to prolong the health of limbs and organs. But work on the brain is lagging behind. The majority of today's incurable diseases affect the nervous system, and understanding the brain is the key to them. But the brain is the most complex part of the body: 100,000 million nerve cells, making a million connections every second of our lifetime. Medical intervention is a delicate matter. Even so, deep brain stimulation has been going on for more than a decade now and is currently used to treat 40,000 Parkinson's sufferers worldwide. Such surgery is going on in London, Bristol and Oxford. We'd better get used to it.

But the memory in the park should give us pause. Who knows what demons from the swamps of guilt and pain might surface at a flash of current? When we deal with memory we are dealing with more than the brain's ability to learn and remember modes of behaviour ... the realm of the scientist. We are also dealing with the essence of the human personality ... the realm of the poet and the writer.

Old people mind about losing their memories. I do myself. "Just remind me," I say to my children, as they reminisce about holidays long ago. And with the stimulus of an anecdote, the reminder of a dress, or a meal, the memories come flooding back. I regularly take folic acid and ginkgo biloba because someone has suggested they help keep the memory in good order. Do they work? I don't know, but I know I'd be furious if years hence it's proved to be so, and I hadn't bothered.

Both these methods – the anecdotal and the pharmaceutical – are consciously made choices to bring back and hold on to a facility that makes me who I am. My concern about the research going forward, which I hugely welcome in its capacity to help Parkinson's and Alzheimer's sufferers, is the unexpected spin-offs it may bring for the human identity. We think we would be happy to have our memories restored. Memories make us who we are: they build our histories and are the source material for our daily judgements and behaviour. But think what a torrent of confusing and contradictory data has been safely stowed away out of daily reach.

Who has not woken in a midnight sweat at the sudden recollection of an awful moment, an incident of huge embarrassment, of wretched childhood misery, or ghastly suffering. The young soldiers back from Iraq wake with traumatic flashbacks because the memories are too painful to live through again. The brain represses many memories for good reason. The memories we relish are of happy times... first love, family laughter, remembered music, the loveliness of nature. It is why we hoard photographs, keep diaries. But consider the failures, the disappointments, the insults, the pain of parting, the grief of loss. Who wants these stirred up again at the prick of science's needle?

This calls for scientists of poetic sensibility.

It is certainly exciting to know such work is going forward. But even as those leading the research write up their findings, submit their experiments for peer judgements and select the patients they feel best able to help, they also need to consider what it is they tamper with. The human brain is more than all those nerve cells making millions of connections every second.

joan.bakewell@virgin.net