Memory Key Newsletter

It’s not inevitable that you experience more memory problems as you get older, but the likelihood that you will experience more memory difficulties in certain specific areas certainly increases as you get older. (Please notice that I say: more problems — we all, regardless of age, experience memory problems! There’s no such thing as a perfect memory — even those very rare instances of amazing memory are limited to a specific area — and every reason to believe a perfect memory is not desirable.)

One of the areas in which older people tend to demonstrate increasing problems is that of source memory: knowing where and when you experienced something. This may sound fairly innocuous, but it can have quite serious implications. For example, warnings about particular products may make you more inclined to buy the product, because the warning aspect isn’t remembered, only the mention of it (and we are more likely to buy products that are familiar to us). Relatedly, older adults have also been shown to be more vulnerable to being persuaded that they remember something that didn’t really happen.

While this problem is well established, researchers are less clear about the cause. In general though, it has been mostly thought of as reflecting a deficit in remembering enough specific details about an experience, which seems logical enough. However, recent work by Chad Dodson and his colleagues has provided evidence for another explanation [1,2]. (I’d like to thank Dr Dodson for sending me copies of these papers, and ask his pardon for my simplification of his interesting thesis).

In this account, older adults’ tendency to misremember (a problem made worse by an accompanying high degree of certainty in their misrecollections) is at least partly due to a tendency to mistakenly combine features of different memories. By dragging in details from other memories, you can ‘fill in the picture’ and create a memory whose detail is utterly convincing (hence your certainty that you have indeed experienced the memory — and hence the unfortunate finding that the likelihood of error is actually greater the more confident the person is that they have remembered correctly!). This miscombining may occur at the time of encoding, in which case features would be taken from events that are temporally close. Or it may occur at retrieval, between events that are similar in some way.

But although they occur at different times, both of these — the miscombining of temporally close events during the encoding process, and the miscombining of conceptually similar events during the retrieval process — probably reflect a failure at the time of encoding. The latter miscombination presumably results from the activation of similar memories together with the target memory, and probably reflects a failure to encode enough of the ‘right’ features (ie, those that will help you distinguish that particular memory from similar ones), and perhaps also, a failure to bind the features tightly enough to form an integrated unit.

These encoding failures may come about as a result of the shrinkage that often occurs in the hippocampus as it ages. (Do note, again, that this is not an inevitable consequence of age, just a characteristic one).

Some support for all this comes from a study that has just been published in Science [3], which reveals that the dentate gyrus — a subregion of the hippocampus, and the one, incidently, where most adult neurogenesis seems to take place — is critical in enabling us to rapidly distinguish similar, yet distinct places or experiences. Crucial to this process of distinguishing similar contexts is a particular protein signalling molecule known as the NMDA receptor.

This all sounds rather inevitable, and thus depressing — that these confused memories and deficits in source memory are the consequence of physiological deterioration that we cannot do anything about. It’s true that certain genes may incline you to these problems, that yet-to-be-developed pharmacological therapies may be necessary for some. But it is not true that you can’t affect the physical structure of your brain.

You have, in fact, done it all your life.

Indeed, you may be responsible for it deteriorating. Alcohol, lack of sleep, stress, all these may reduce your hippocampal tissue (number and complexity of neurons). But you can also achieve positive change. In recent years, a number of studies have come out providing evidence that adults can produce new neurons in their hippocampus (see http://www.memory-key.com/Neurology/neurogenesis.htm for more about this). The main method of achieving this that we currently know of is through mental and physical stimulation. I’ve spoken about this elsewhere (see http://www.memory-key.com/Seniors/stimulation.htm ), so let me just mention a new website I’ve been told of, that provides games to improve your memory, attention and processing speed. It’s free at the moment, while it trials, so if you’re interested, now’s the time to try it! The address is http://www.lumosity.com/. But don’t forget either the benefits of physical exercise.

You can also work on a more targeted strategy. Just because there may be physical changes in your brain that compromise brain function doesn’t mean that deficits in function are inevitable! You can learn new strategies that employ different parts of your brain. So in this case, since the problems appear to be encoding ones, the answer lies mainly in attention — you need to be more attentive, deliberately paying attention to those aspects of the event (a word I’m using as a global term for any experience or piece of information you want to remember) that will help both categorize it and distinguish it from its other category members. Some of those aspects may be quite irrelevant to the content itself, to what you need to remember, but are usefully noted because they are more memorable and will help distinguish the event.

1. Dodson, C.S., Bawa, S. & Slotnick, S.D. 2007. Aging, Source Memory, and Misrecollections. Journal of Experimental Psychology: Learning, Memory, and Cognition, 33 (1), 169–181.

2. Dodson, C.S. & Krueger, L.E. 2006. I misremember it well: Why older adults are unreliable eyewitnesses. Psychonomic Bulletin & Review, 13 (5), 770-775.

3. McHugh, T.J. et al. 2007. Dentate Gyrus NMDA Receptors Mediate Rapid Pattern Separation in the Hippocampal Network. Science, Published online ahead of print June 7.
http://www.physorg.com/news100444183.html
http://www.sciam.com/article.cfm?articleID=0D7230B5-E7F2-99DF-33A3DA38AE4500AC&chanID=sa011

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WEBSITE DEVELOPMENT

My apologies for the absence of last month’s newsletter. This website redesign has been dragging on so long, and preventing me coming to grips with all the things I should be doing (like writing books and getting my courses up and running), that last month I simply flagged the newsletter away in the hopes of getting the redesign finished. I didn’t succeed (otherwise this month’s newsletter would no doubt be going out on time!), but I have made huge progress, and hope to complete it soon. I have, at least, made enough progress to persuade me to restart my blog entries, which also have been in hiatus for some time.

The redesign of my site, I hasten to add for those who may think I’m frittering my time on trying to make it ‘cooler’, is aimed at making the information on the site much easier to find, and making it easier for me to keep it properly updated. It has, over the years, grown like Topsy, and even I have to think a bit before knowing where to look for a specific article! And so much of it is interconnected, it can’t rely on me remembering to update all the relevant sections all the time.

I also find, as I progress with the organization, that it makes it much clearer for me to see where there are ‘gaps’ — articles begging to be written, to fill in some information lack. So, lots of upside, and I think you will find the end-product worthwhile.

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BLOG

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