Why does memory change as we age? What changes?

As the baby boomer generation begins to enter seniority, concerns over mental performance for that age group are drastically increasing. Supposed brain training games like luminosity are attempting to cash in on this generational concern, but how is memory actually changing as the brain ages? Research seems to indicate that while episodic and source memories are affected by normal aging, semantic and procedural memory stay rather intact. Scientists believe this is due to how different regions of the brain atrophy during aging.

For example, Nyberg and colleagues found that episodic recall varied according to age but that semantic memory did not show this negative relationship. Thus older adults might struggle with remembering if they took their vitamin supplements that morning, but seemed to have no problem identifying the current president. In addition, memories for how to carry out actions seem completely spared. In studies using animal models, researchers found that aged animals performed equally well on an obstacle course compared to the younger animals (as long as gross motor control was normalized across groups). This explains why my 62-year-old mother is one of the best nurse anesthetists at her workplace, even when she might feel that some of her memory is eroding.

So why aren’t all memories made equal with respect to aging? Shouldn’t all types of memory decline equally as we age? Region-specific atrophy seems to be one of the key components in this dissociation longevity between the types of memories. In an imaging study conducted by Yonelinas and colleagues, healthy older adults showed reductions in hippocampal volume when recollection was diminished. Meanwhile recognition performance was dependent on entorhinal volume. These regions of the brain, found in the medial temporal lobe, tend to decrease in volume to a greater extent during aging than other regions. Whether these volume changes are due to the dying-off of neurons or reduction in synaptic connections, this seems to be a major cause of memory complaints in older adults.

So it is rather unfair to say that memory declines as we age, when not all memory is created equal. It is noticeable in daily life to recognize that you can’t call to mind where you met someone or how to use a computer function that your children just taught you. It is not immediately obvious that your memory of how to drive a car or ride a bike is still almost completely intact. I believe this is due to our limited connotation of the word ‘memory.’ When taking all forms of memory into account, healthy aging does not cause nearly the impairment that might be felt by an older adult. Because we rely so heavily on episodic and source memory in our social lives, we might not realize the multitudes of semantic and procedural memories that have been spared. Maybe brain-training games are effective, but it is important to also remember that an aging mind isn’t deficient in all memory types and that much expertise is actually spared.

Churchill, J. D., Stanis, J. J., Press, C., Kushelev, M., & Greenough, W. T. (2003). Is procedural memory relatively spared from age effects?.Neurobiology of Aging, 24(6), 883-892.

Nyberg, L., Bäckman, L., Erngrund, K., Olofsson, U., & Nilsson, L. G. (1996). Age differences in episodic memory, semantic memory, and priming: Relationships to demographic, intellectual, and biological factors. The Journals of Gerontology Series B: Psychological Sciences and Social Sciences, 51(4), P234-P240.

Yonelinas, A. P., Widaman, K., Mungas, D., Reed, B., Weiner, M. W., & Chui, H. C. (2007). Hippocampus, 17(11), 1134-1140.

Memory in the aging brain: doubly dissociating the contribution of the hippocampus and entorhinal cortex.