Instead of being forced to confront the present, some dementia patients are being helped to enjoy their pasts. A trip down memory lane can offer a new lease of life, discovers Markie Robson-Scott.

"Everything is lost because there's no sugar." Brenda Deal leans back in her chair and looks beseechingly at her son Graham, who goes to get the sugar for her cup of tea from the kitchen staff. "I think they can handle him," she says to me and laughs. We're in the Memory Lane unit of Tandridge Heights, a Barchester care home in Oxted, Surrey, where Brenda, who is 87 and has vascular dementia, has been living since 2006, surrounded by a surreal collection of vintage items used for "reminiscence sessions": wedding dresses, handbags, hats, a typewriter on an old desk, a pram full of dolls. A plump tortoiseshell cat washes its face on a chair beside us.

It's a far cry from the bland dementia-floor lounge, telly on, in the Bupa nursing home where my mother, who also had vascular dementia, spent the last two years of her life. On the walls of Memory Lane are posters of Marilyn Monroe, Audrey Hepburn and Marlon Brando, as well as collages of photographs of the residents. Among them is one of Brenda on a golfing range. She was a champion golfer in her ex-pat days in Trinidad in the Fifties when her husband worked for an American oil company.

"She's still got a great back swing," John Lavan, the manager, tells me. "She recently hit the ball dead straight, a drive of 150 yards."

Memory Lane is all about living in the past, which of course is where, mentally and emotionally, many with dementia and Alzheimer's exist. There are memory boxes outside each of the 34 rooms, full of things connected to former lives: a machinist has cottons and pieces of fabric, a nurse has her old certificates, a retired colonel his medals. Photo albums of the residents' lives are crucial – my mother didn't remember that my father had died 29 years ago but she could remember the names of all their friends from the Fifties and Sixties when looking at photos – though her rather bleak verdict was: "It's all quite meaningless, so different from the way things actually were." Brenda is happy to go through her album, meticulously captioned by Graham ("Make sure I leave this to someone in my will," she tells him) three or four times a week. It starts with her babyhood in the Twenties and includes her days as a town clerk's secretary – "A very good job, I loved it" – glamorous amateur dramatics in Trinidad, weddings and births of great-grandchildren. "And each time it's new to her," says her son.

She turns the pages slowly. "Who's that?" he asks.

"Well now," muses Brenda, "that must be you."

"No, it's your husband. You were married for 56 years, that's all."

"Oh, I say," she laughs. "No one told me."

The good news is that dementia care is changing, though in some care homes you wouldn't know it. A few years ago, says Sheena Wyllie, director of dementia services at Barchester, it was all about reality orientation. "Regardless of where people were on their journey, you would get them to repeat, 'Today is Wednesday 29 July 2009'. It didn't mean a lot to them. And if they said, 'My mum's coming', which is really about comfort and not feeling safe, we were supposed to say, 'Your mum died 30 years ago, don't you remember?' which always felt really wrong. I could never do it. You could see the distress of their faces."

Now it's about person-centredness, validation, supporting people in their dementia. If someone can't tell day from night – my mother for one – and wants to be up at 3am cooking eggs and bacon, says Sheena, "we help them do it". I think back to my mother telling me that her twin brother, who died in 1990, was down the corridor with his girlfriend and that she needed me to get a handkerchief from them. I knew that the only way to satisfy her was to pretend to look for them – but if I hadn't been there, the staff, who were kind but often overworked, would probably not have had time to investigate. And even Barchester might have found it hard to cope with my mother's temporary obsession about finding the right volume of Sigmund Freud's complete works (she and my father had translated volumes of Freud's letters, though not in the Penguin edition she was convinced was lurking on her shelves).

At Memory Lane, if someone says their mum is coming, the staff try, in quite a Freudian way, to find out where the emotional discomfort lies. One resident, says Sheena, became difficult in the afternoons. "He'd ride around on chairs in a challenging manner and the family didn't know why. Then a carer asked a regular visitor if he knew what this action might be associated with and the friend remembered that he'd had a smallholding ages ago, way before he married, and that he'd go down there in the afternoons on a small tractor." So the Barchester gardener took the man on the back of his grass-cutter every afternoon. "He didn't do any gardening, but the trip was what he needed. He recreated that past occupation. In the old days he would have been labelled aggressive and in need of medication."

Penny Garner, creator of the SPECAL method (Specialised Early Care for Alzheimer's) believes that carers can create lifelong wellbeing by learning how to access the good feelings involved in these past occupations. "If for some reason it isn't possible for that man to go on the grass-cutter, then you have to find a way to recreate that feeling for him through language and gesture." Someone who has moved a lot may be obsessed with packing and unpacking. Nellie, one of Garner's clients, who'd moved 23 times during her marriage, created mayhem in her house with her constant emptying of drawers and cupboards. This ended once she was provided with a trunk to pack and unpack, and as her dementia progressed the trunk became a handbag and the packing turned into the minimal folding of a handkerchief.

Some people can't recreate their occupation but still find dignity in being able to do things. Bob James, who was a local newspaper editor, is spending his time at Hickathrift House in Cambridgeshire writing a review of Michael Parkinson's biography. "He often tells the staff about all the people he's just met on a train journey and they don't contradict, they just say, 'How interesting,'" says his daughter. "And when he showed bizarre and out-of-character behaviour recently, they were fantastic. Their strategy was to emphasise the positive. I think it was because after six months there he suddenly realised this was permanent."

Christine Lyall-Grant was a copy editor at Cambridge University Press until 10 years ago when she started making the wrong proof marks and was diagnosed with Alzheimer's at the age of 59. In February she went into Oaklands, a Barchester care home in Cambridge. A few years ago ending up in a home was her greatest dread. "She was very difficult to place," says her daughter Fiona, a research associate at Cambridge University, "partly because her intelligence is still intact even though her memory isn't." She looked at half a dozen places before she found Oaklands. "In the other places people were just sitting around with nothing going on, often stuck upstairs, locked into the dementia ward. Here she's got access to a courtyard where she can come and go as she pleases, she can water plants, see the sky and breathe the fresh air. She's forgotten about being an editor but she likes to keep busy, though she's got no interest in baking cakes, which other residents love – she never baked. But she loves the art therapy as she always visited art galleries. And she loves going to Tesco with the staff."

My mother might have been too far along in her "dementia journey", as the Barchester people put it, to keep busy or to appreciate the pram full of dolls and the rummage boxes stuffed with fabric ("they enjoy the textures", explains John Lavan). Do some people find these areas confusing or threatening? "It's important to make sure it doesn't trigger behaviour that can cause distress to them or others," says Sheena Wyllie. Penny Garner agrees. "You do have to do a risk management strategy. A pram with dolls could upset someone who'd lost a baby, for example."

Although person-centred dementia care is accepted as a model, in many places it's still a matter of lip-service. As Sheena Wyllie says: "The general experience in this country for old people, if you're not fit, healthy and wealthy, is not a good one. Is this what we really want for ourselves?" Even the best care home staff can't fully appreciate what a person was really like before they had dementia but huge efforts are being made. Perhaps some even glimpse that dementia, with its Benjamin Button-like quality of growing younger and younger, has, as Garner says, "a magic element that people often miss".

Tender treatment: Person-centred care

* Person-centred dementia care, based partly on the work of the late Tom Kitwood and the Bradford Dementia Group, is less concerned with the symptoms of dementia than in searching for the subjective reality of the person with the disease.

* It closely involves the family and friends of the person with dementia, recognises and supports the personal history of the individual and focuses on bringing out the best in someone and on how they are feeling.

* Memory Lane units use memory boxes to help identification of bedroom doors; sensory gardens; baking; arts and crafts, pet care, doll therapy, music therapy and reminiscence therapy.

* Fees at Tandridge Heights Memorial Care Home, Memorial Close, Oxted, RH8 0NH: £650-£1,200 a week, depending on level of care and funding.

* In the UK, 700,000 people suffer from dementia; it will exceed a million by 2025. 64 per cent of care home residents have dementia.

* Two-thirds of people with dementia are women.

Contented Dementia by Oliver James (Vermilion, £12.99) is a guide to Penny Garner's SPECAL method.