Memory Lame: Why You Keep Forgetting Things
How Memory Works
My friend Patty dubs it a Swiss cheese moment, though mine lasted for a month. I couldn't find the shopping bag containing two pairs of pants I needed to return. I knew I'd set it aside somewhere but my repeated, frantic searches found nothing. Then, long after I'd given up hope of ever finding the darn thing, I reached into my raincoat pocket and found a receipt from the store -- I'd returned both pairs a few weeks earlier. But I had absolutely no recollection of doing it. That's when mild panic set in: Is something really serious going on?
"Misplace your keys when you're 30 and it's no big deal," says neuroscientist Susan De Santi, PhD, an expert in brain imaging and cognition. "But at 40? People start to get concerned."
They sure do. My mind went straight to early-onset Alzheimer's. Once I'd talked myself out of that diagnosis, I settled for garden-variety age-related memory loss. Which still panicked me -- if I was this bad now, what were my retirement years going to be like?
If you've had that same kind of experience, don't freak out, says Dr. De Santi. "Everybody has moments when they forget something for a host of reasons that has nothing to do with aging or Alzheimer's." Sure, aging is a factor in memory loss, the same way you may not run as fast in your 40s as you did in your 20s. And while you lose neurons as you age, your brain makes new ones. There's a big difference between normal slowing down and serious cognitive impairment, Dr. De Santi says.
Even if there is something going on with your memory, it's unlikely to be Alzheimer's. "Many psychological and physical disorders that have nothing to do with aging can weaken memory," says psychologist Mark A. McDaniel, PhD, coauthor of Memory Fitness: A Guide for Successful Aging. Common culprits include an over- or underactive thyroid, anxiety, low blood sugar, and medications such as antidepressants and antihistamines. If you're perimenopausal, fluctuating hormones can also play a role -- the same hormones that, years earlier, may have caused "pregnancy fog."
A visit to your doctor is a good idea if you're suddenly forgetful. But for most people memory glitches are nothing to worry about. "Such fogginess is most likely caused by treatable, reversible conditions," Dr. De Santi says.
Every piece of new information (such as, here I am at the store, returning the pants) triggers a complex series of chemical and cellular changes in your brain. To remember something new your brain must encode the information, store it, and later retrieve it. A breakdown in any one of those three steps leads to forgetting.
"Encoding involves all the senses -- vision, hearing, smell, taste, touch," says developmental molecular biologist John J. Medina, PhD, author of Brain Rules. How much you recall is influenced by what's happening around you at the time you're encoding as well as by your previous life experiences -- including genetics. Your brain takes in the new information and splits it into millions of pieces, sending them off to various parts of the brain: sounds in the area devoted to auditory processing, colors in the visual processing regions, and so on. Then it brings it all back together again (or not) when you try to recall something.
There are two main categories of memory: short-term and long-term. Short-term memory lasts only a few seconds -- you call 411 for the phone number of a new restaurant and unless you jot it down or repeat it several times you probably won't remember it after you make the reservation. Most people can hold only about seven bits of information (digits, letters, words) in their head at a time unless they do something to move that fleeting memory into long-term storage. There's a reason for that: If your brain held on to every piece of information it would be so cluttered you couldn't function. On the other hand, the smallest interruption deletes what you want to remember. That's why you may walk into a room to get a book, be distracted by someone asking when dinner will be ready, then stand there and wonder why you went into that room.
Long-term memory is a bit of a misnomer: It can mean something learned five minutes, or five years, ago. There are several types of long-term memory: Declarative memory is a memory for facts (such as "Thomas Jefferson was the third president of the United States"). Episodic memory is linked to a particular time and place (last summer's camping trip; where you went for your first anniversary). And motor memory governs everyday things like remembering how to brush your teeth.