Short-Term Memory Loss

What’s Normal? When Should You Worry About Dementia? 

We all experience occasional episodes of memory loss. You forget where you put the keys or can’t remember the password to your PayPal account. You fear this is a sign of serious problems to come.

One of my greatest fears is I’ll be out driving one day and not remember where I am going, or worse, how to get back home.

How bad do memory problems have to get, you may wonder, before they become signs of Alzheimer’s?

Neuroscience divides memory into many different types: implicit or non-declarative memory, declarative memory, semantic memory, episodic memory, and others. For our purposes, there are only three that matter: (1) short-term memory, (2) working memory, and (3) long-term memory.

Short-term memory is the brief period during which you can recall information you were just exposed to. When you walk out of a movie theater you remember quite a few details about the movie you just saw—names of main characters, sequences of events, dramatic scenes, the music … perhaps even minutiae like what the type font looked like on the credits. By the time you get home you have probably forgotten some things. “What was the name of the character who jumped off the bridge?” you might wonder. After a few hours or days, you won’t be able to recall much detail but you’ll remember the general idea of the movie and whether you liked it or not. Weeks later you will still remember the experience of the movie, but you may have forgotten the title.

Working memory is similar to short-term memory. It is the ability of our brains to keep a limited amount of information available long enough to use it. Working memory helps you process thoughts and plans, and carry out ideas. It combines immediate details with knowledge and strategies from your long-term memory bank to help assist you in making a decision or calculation.

When I think of working memory, I picture a quarterback in the huddle of a football game. Short-term details in his working memory include what down it is, how many yards to go, and what happened the last few plays. Based on his experience he knows how risky it is to throw a pass on the next play, or try a pitch out to his running back. He remembers his coach telling him, though, that the opposing defense has trouble defending short passes in the flat. So he calls a passing play to his tight end.

Long-term memory encompasses memories that range from a few days to decades. Unlike short-term memories, these are relatively permanent.

Many older people experience problems with memory loss (mostly short term), sometimes referred to as “age-related” memory loss. It is debatable whether short-term memory loss is caused by age or is the result of other factors: lack of exercise, sleeplessness, perhaps stress. This common memory loss can become alarming, though usually it does not.

Here are some differences between “normal” memory loss and memory loss associated with dementia:

• Forgetting part of an experience is normal. Forgetting the whole experience could be a sign of dementia.
• Forgetting the name of the waitress at your favorite restaurant, and then recalling it later is normal. Not recalling it at a later time or forgetting that you forgot is more serious.
• Even with some short-term memory loss you have no problems following instructions, verbal or written. A person with dementia is less and less able to follow instructions over time.
• Keeping notes on your iPhone so you won’t forget to pick up toilet paper and dog food next time you are at the grocery store is helpful. This is of no use to a dementia patient. If they do remember taking notes on their iPhone they will forget how to access them.
• People with “normal” memory loss can manage all aspects of their personal care—bathing, dressing, brushing their teeth. People with dementia lose their ability to take care of themselves.