episodic memory

When a middle-aged woman loses her memory after sex, it naturally makes the headlines. Many might equate this sort of headline to “Man marries alien”, but this is an example of a rare condition — temporary, you will be relieved to hear — known as transient global amnesia. Such abrupt, localized loss of autobiographical memory is usually preceded by strenuous physical activity or stressful events. It generally occurs in middle-aged or older adults, but has been known to occur in younger people. In those cases, there may be a history of migraine or head trauma.

Following a 1994 study that found that errorless learning was better than trial-and-error learning for amnesic patients and older adults, errorless learning has been widely adopted in the rehabilitation industry. Errorless learning involves being told the answer without repeatedly trying to answer the question and perhaps making mistakes.

In a recent study, 40 undergraduate students learned ten lists of ten pairs of Swahili-English words, with tests after each set of ten. On these tests, each correct answer was followed by an image, either a neutral one or one designed to arouse negative emotions, or by a blank screen. They then did a one-minute multiplication test before moving on to the next section.

On the final test of all 100 Swahili-English pairs, participants did best on items that had been followed by the negative pictures.

Given all the research showing the importance of sleep for consolidating memories, it should come as no great surprise that the reverse is also true: depriving yourself of sleep could help you forget experiences you would prefer not to remember.

A mouse study has revealed the brain becomes overly stimulated after a traumatic event causes an ongoing, frenzied interaction between two brain proteins long after they should have disengaged. However, the injection of newly developed drugs into the hippocampus within a five hour window calmed this process, and prevented the development of a post-traumatic fear response.

The role of sleep in consolidating memory is now well-established, but recent research suggests that sleep also reorganizes memories, picking out the emotional details and reconfiguring the memories to help you produce new and creative ideas. In an experiment in which participants were shown scenes of negative or neutral objects at either 9am or 9pm and tested 12 hours later, those tested on the same day tended to forget the negative scenes entirely, while those who had a night’s sleep tended to remember the negative objects but not their neutral backgrounds.

Confirming earlier research, a study involving 257 older adults (average age 75) has found that a two-minute questionnaire filled out by a close friend or family member is more accurate that standard cognitive tests in detecting early signs of Alzheimer’s.

The AD8 asks questions about changes in everyday activities:

Reports on cognitive decline with age have, over the years, come out with two general findings: older adults do significantly worse than younger adults; older adults are just as good as younger adults. Part of the problem is that there are two different approaches to studying this, each with their own specific bias. You can keep testing the same group of people as they get older — the problem with this is that they get more and more practiced, which mitigates the effects of age.

Children’s ability to remember past events improves as they get older. This has been thought by many to be due to the slow development of the prefrontal cortex. But now brain scans from 60 children (8-year-olds, 10- to 11-year-olds, and 14-year-olds) and 20 young adults have revealed marked developmental differences in the activity of the mediotemporal lobe.

A number of studies have found that source memory (knowing where you heard/read/experienced something) is a particular problem for older adults. Destination memory (knowing who you’ve told) is an area that has been much less studied. Last year I reported on why destination memory is difficult for all of us (my report is repeated below). A follow-up study has found not only that destination memory is a particular problem for older adults, but that it is in fact a worse problem than source memory.