Derek Burnett
Derek Burnett is a Contributing Writer at Bottom Line Personal, where he writes frequently on health and wellness. He is also a contributing editor with Reader’s Digest magazine.
Hopefully, you’re already aware that occasional lapses in short-term memory, especially as we age, are common. If you can’t remember where you put your reading glasses or have forgotten whether you took your vitamin this morning, that’s usually not cause for alarm. You can write off such lapses to distraction or disruption, or even to normal age-related memory loss.
But what if you can no longer remember your elementary-school teachers’ names? What if you’ve forgotten the words to a song you used to know by heart? What if you used to be able to tune a guitar but now wouldn’t know where to begin? Having lapses in long-term memory can be even more frightening than short-term deficits. After all, if you can forget things you used to know well, does that mean you’re on your way to being unable to recognize your family members or to know who you are?
Fortunately, it’s common to lose long-term memories without having any form of dementia. Let’s delve a little into how long-term memory works.
To create a memory, the brain undertakes three steps, called encoding, storage, and retrieval.
Encoding occurs when we’re first exposed to the raw cognitive material of which the memory will consist. That could be witnessing an event, hearing a new word, watching a movie, learning a trivia fact, and so on. It could even be watching a bird flit past your window. Your senses are taking in impressions that give you access to the new bit of knowledge, whatever it is.
Storage is the process of your brain deciding what to do with the data. When that data first hits your brain, it resides there as working memory, also called short-term memory. The overwhelming majority of the information you take in spends a fleeting amount of time in working memory and then is discarded, replaced by what’s new. The bird flitting past your brain might register ever so briefly and then disappear out of memory, since you have no need for it.
Imagine a typical morning in which you rise from your bed, go to the bathroom, walk into your kitchen, turn on the coffee pot, and begin preparing breakfast. Most of what you do and sense during those moments is insignificant and automatic. Although your senses are being treated to plenty of stimulation, there’s little that you’re motivated to remember. Perhaps when you sit down to breakfast, you note idly that the digital clock on the stove reads 7:03. For how long will you recall that fact? Perhaps for a few seconds, or maybe even on into the afternoon. But certainly you won’t retain the exact times at which you’ve sat down to every breakfast in your life. You’ve got better things to do with your brainpower.
But what if, just as you sit down to breakfast and note the time, there’s a huge fireball outside the window as a gas main across the street blows up? You’ll later be able to tell the authorities that you witnessed the explosion at exactly 7:03, and some day years from now when you’re telling the story, you might say, “And I still remember, it was exactly 7:03 a.m. when it happened.” That’s because suddenly the time you sat down to breakfast has become very important to you, so you immediately began reinforcing it in your mind, nudging it out of working memory into the part of your brain where long-term memories are stored. Each time you recall the fact that the explosion occurred at 7:03, the memory becomes more solidly imprinted in your mind.
You do something similar each time you try to memorize information. Medical students are famous for creating flash cards to help them move what they’ve learned about human anatomy into their long-term memories, through repetition. Students of language do the same thing with vocabulary, and would-be geographers memorize maps and capitals through repetition.
There are three main types of long-term memories:
No matter the type of memory, its status as long-term is no guarantee that we’ll never forget it. Accessing memories reinforces them and keeps them alive. In fact, if you “remember” an episode from your early childhood, you’re probably not remembering it directly but rather are remembering it as you’ve described it to others or replayed the scene in your mind. If a memory sits unrecalled for too long, it begins to fade away. Thus, while some kinds of memories are “stickier” than others, there is a use-it-or-lose-it aspect to long-term memory. It could be that you’ve forgotten your elementary teachers’ names simply because you haven’t thought or talked about them in many years. It’s thus perfectly natural to come up empty-handed when you try to dredge up the memory, even though it might feel shocking to discover that you’ve forgotten it.
Of course, not all lapses in long-term memory are merely the result of this use-it-or-lose it principle. People suffering from Alzheimer’s dementia begin to lose their long-term memories, although usually in the disease’s later stages.
Other serious causes of long-term memory loss include damage to the brain from:
Trying and failing to dredge up some old factoid or rusty skill should not be cause for alarm. And you should expect some mild long-term memory loss as you age. But long-term memory loss deserves attention if it begins to disrupt daily life. For example, if you notice that you or a loved one are having trouble finding your way along familiar roads, forgetting very common words, forgetting how to perform skills used daily, or mixing up words (replacing “TV” with “computer,” for example), cognitive testing may be in order. That’s especially true if the memory loss is accompanied by confusion or disorientation.
You might find that your memory loss is reversible, since it could be caused by a drug you’re taking, by a vitamin deficiency, or by a mental-health problem such as depression or stress.
Nearly 20% of US adults over age 60 are estimated to suffer from mild cognitive impairment (MCI), an intermediate form of memory loss more severe than normal age-related memory loss but less severe than dementia. The majority of MCI cases do not progress to dementia.
