Adult Absentmindedness

As I have aged (I recently entered my 75^th year), I have increasingly experienced a phenomenon that most anyone over 50 can attest to: there is a chunk of memory, say, a word, that you are positive is stored deep in your brain, but at the moment refuses to be recalled. You are either thinking to yourself or talking to someone, and in mid sentence, the next word just won't come. It can be a minor irritation or it could seriously rattle your cage, as the threat of Alzheimer's comes to mind... but not that damned word!

My wife and I know each other well enough by now that we can usually save our spouse fretting over such a brain fart, by supplying the missing word for the other. That's only a minor consolation, however, since the affliction seems to continue to grow as we age. Maybe we can try learning how to read minds.

I decided to grasp onto a little consolation a few years ago, when I conjured up the notion that my brain is not deteriorating—it's simply the case that I've continued to cause it to soak up so much new and wonderful information that it's become fully saturated with knowledge. As I add more new things, some of the old, stale things necessarily get pushed off my mental plate—they get purged from my memory banks. Although I liked the sound of that notion, it really was little comfort, since I had to admit that it might just be wishful thinking.

Then I was rescued this last spring, when researchers announced that they had discovered the cause of something dubbed “infantile amnesia.” Although this refers to a person's general inability to recall events before about age three, the process can also occur later in life, the scientists said. The cause (the culprit): something called “neurogenesis”—when new neurons in the brain rearrange its connections and destabilize existing memories.

We humans are born with an incomplete brain. (If it were any more complete than it is at birth, our head would be too big to squeeze through mom's birth canal.) So, in the first few years we grow many new neurons at a rapid pace, as our skull doubles in size. All this new gray matter disrupts existing neurons, trashing some of those early infant memories.

So what about us elders? Up until a few years ago, neuroscientists believed that an adult brain cannot grow new neurons—only kids can. Now we know that's not the case. We old farts can do it too.

Where does this leave me (and countless other elders)? Well, if we are able to generate new neurons, there's the possibility that they then muscle in and trash some of our earlier memories. Aha! That's why I can't remember that word! My earlier notion that new knowledge is pushing some old memories off my mental plate is not so unlikely after all. OK, so I lose a few memories: but look at all the new ones I can gain at my age!

Now... what was that next neat idea I was gonna write about...?