YOU MUST REMEMBER THIS: WE ALL FORGET
Where were you on the afternoon of 31 August 1997? Think hard and you may remember.
To recall the day, you will have to search through layers of autobiographical memory and try to make associations with that date. If you are still struggling, perhaps this will help: that afternoon, in Australia, the death of Princess Di was announced.
Now that you know this, you probably recall where you were.
Memory is a strange and subtle faculty. When you lay down a memory, theoretically it is there forever. It may become overwritten and seem irretrievable but years down the track you may remember it. Usually, however, this sort of personal memory attenuates unless it has a major association.
One of the main anxieties of ageing is that memory seems to become harder to access. This anxiety is deepened by confusion about different types of memory and what a deficit in one or another of these types might mean.
The two forms of memory that are usually first to be affected in middle age are prospective memory and the act of word retrieval. Prospective-memory loss results in your forgetting what you intended to do. You walk into a room and can’t remember why you are there.
In the case of word-retrieval problems, the word is on the tip of your tongue but you just can’t get it at the appropriate time. Generally, it comes to you later. These word-finding and prospective-memory problems are mostly minor hiccups – signs that the brain, at that moment, is not working at its optimal level. Everyone experiences such inefficiencies.
These two forms of memory are vulnerable to the distractions of everyday life. Essentially they reflect a state of overload or poor organisation that can be worsened by stress, fatigue, the consumption of drugs or alcohol, or trying to do several things at the same time.
Behind memory issues lurks the big worry about Alzheimer’s disease. While slips of memory in youth go unnoticed, slips in middle age generate concern. When a 50-something man can’t remember conversations he has had, he fears he is heading for early-onset dementia.
But there is a crucial difference between a worried well person and a person with incipient Alzheimer’s. When there is a difficulty retrieving information, a worried well person will get it eventually. The memory is still available but not accessible at that point. The person with the incipient Alzheimer’s has probably lost that information forever. The memory was never laid down and will never come back. People with Alzheimer’s cannot store new memories – they are in a state of pure forgetting.
There is a well-known case of a Montreal man, referred to as H.M., who had brain surgery for epilepsy in 1953. He was in his 20s at the time, and not only did the surgery fail to cure him, but it also robbed him of the ability to lay down new memory.
Today he is in his 60s but his world is locked in the early fifties. Although intelligent, he does not know the meaning of words that have appeared in English since then, such as ‘aerobics’ and ‘reggae’. He also does not remember people he has met since 1953. You can spend a day with him, but the minute you walk out of the room, he forgets you entirely. His case was important for neuroscientists because it demonstrated that there was a specific part of the brain that is vital for the laying down of memory. This is the same part of the brain that is damaged early in Alzheimer’s. In healthy people, the ability to remember depends on the way memory was laid down and how much work you are prepared to do to retrieve it. If it was laid down with the intention of being recalled or with a strong association, it will be easier to access.
The issue of working up a memory is more complex. You wouldn’t think about a pothole in the road today but tomorrow, when you drive over it again, you will register that it was there yesterday. Remembering this required no work. But try to recollect what you ate for lunch last Monday: that takes work.
While it is a myth that memory is a muscle that can be exercised and strengthened, there is evidence that the more active it is, the more active it will remain.
Experts are sceptical about courses that claim to boost memory power. Those who conduct these courses, they say, are little more than travelling snake-oil merchants who demonstrate their powers by remembering the names of everyone in the room. It’s a gimmick.
While such courses may help people to remember long lists of items or numbers, they won’t help them recall Monday’s lunch. You cannot be trained to access information but you can be trained to encode information more efficiently so that you can retrieve it more easily.
School children who commit pages of Latin and history to memory are not training their memories, nor are they strengthening any memory muscle. A big store of facts is, however, useful in itself, both to increase your knowledge and to help you make useful mental associations. This store is housed in the semantic memory, which is an encyclopaedia-like repository of all the facts you have ever known.
People with semantic dementia (which affects different regions of the brain from Alzheimer’s) experience a shrinking of their memory store. It shrinks in virtually the opposite sequence to the way it would have expanded when they were children. Children’s knowledge expands, for example, from recognising a ‘doggy’ to being able to identify different breeds. Adults with semantic dementia might once have known every breed, but gradually they lose this information and ultimately might be left only with the word ‘dog’ to describe all four-legged animals. Eventually, they lose even that word.
Fortunately, semantic dementia is very rare. The good news is that most of us won’t get Alzheimer’s either. Even though the risk of Alzheimer’s increases as we grow older, by the age of 95 it is no more than 50 per cent. Most of us won’t live long enough.
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