Most people (including most memory researchers) would agree that the ability to learn new information tends to decline a bit with age, even in healthy individuals free of Alzheimer’s disease or other age-related disorders. Eighty-year-olds simply don’t learn as well as forty-year-olds do, and – if the truth be told – forty-year-olds don’t learn as well as twenty-year-olds. For most elderly individuals, this is a mild decline in learning that doesn’t impair daily life beyond an occasional annoyance – forgetting the location of the car keys or momentarily blanking on the name of a new acquaintance.
One thorny question has always been whether this age-associated impairment reflects a failure of learning or of retention. Are older people less able to learn (encode) new information – or do they successfully learn the information but then fail to retain it, perhaps due to accelerated forgetting?
A new study in mice suggests that the age-related impairment is one of learning, not forgetting. Louis Matzel and colleagues tested young mice against mice aged 19-21 months (a ripe old age for mice). Unsurprisingly, the elderly mice were slower than young mice on several kinds of learning tasks. But, with extended training, this deficit could be overcome, so that the overtrained elderly mice performed as well as their younger counterparts.
The new twist in this study was that both groups of mice were tested on their learning after an interval of 30 days. The younger mice tended to remember well. The older mice who had been overtrained could also remember well. Only the elderly mice whose initial training had been incomplete showed poor performance on the retention test. This suggests that, once the elderly mice do learn the information, they do not forget it at a higher rate than young mice. The trick is to use overtraining to get the information properly stored in the first place.
Obviously, mice are not people; but some important facts about learning and memory that have been observed in mice turn out to be true in other mammals too, including humans. In this case, the conclusion would be that elderly individuals may need a little longer to get new information safely stored in the brain. But once safely stored, that information may be no more vulnerable to forgetting than in a younger brain.
Further reading:
L. D. Matzel and others (2009). “Age-related impairments of new memories reflect failures of learning, not retention.” In, Learning and Memory, vol. 16, no. 10, pp. 590-594.
