By Margaret Renkl

MARCH 20, 2000:  It's been gradually dawning on me that I used to be smarter than I am now. This is not a metaphorical statement, not one of those baby-boomer aphorisms that go something like "When I was young, I thought I knew everything, but now that I'm older, I see how much I still have to learn." No, I'm speaking entirely literally. There was a time not too long ago when I knew more, learned more quickly, and remembered what I learned with vastly greater accuracy. I could recall medical statistics, the names of people I met at parties, and whole Shakespearean speeches. I could put a book down and three days later resume reading exactly where I left off, without backing up for a refresher dip in the previous chapter.

Not any more. These days, if I haven't misplaced the car keys, I've forgotten where I parked the car. Now, partly this is a function of owning an anonymous set of wheels: When you drive a white minivan, you can spend most of a morning wandering around the sea of cars in the Galleria parking lot, approaching van after van without coming anywhere near your own Moby-Dick of the automotive world. And partly, too, it might well be the effect of encroaching middle age. At 38 years old, my brain probably isn't quite as elastic as it was at 20, and I'm willing to cede that point.

But it turns out I'm not suffering early-onset Alzheimer's at all, judging from a report last week from the Laboratory of Neurophysiology at the Massachusetts Mental Health Center in Boston. Apparently, there's a direct correlation between remembering newly gained information, such as where you parked your car two hours before, and plain old garden-variety sleep deprivation.

These researchers believe there are two specific stages of sleep--the first two hours and the last two hours of an eight-hour night--during which the brain undergoes chemical and physical changes that enhance memory function. If sleep is interrupted during the first phase, or cut short during the last, new information retrieved during the previous day takes longer to recover, or is lost altogether.

It's true that I'm slower on the uptake than I used to be, but it didn't take me all that long to get the point of this research as it applies to my own apparently calcifying brain function: I'm getting more stupid not because I'm getting older but because our kids won't stay in their beds all night long.

Here's how a typical night goes at our house:

7:30 Youngest boy goes to bed.

8:00 Middle and oldest boys go to bed.

9:30 Parents go to bed.

10:30 Baby monitor wails; baby has lost his pacifier. Parent retrieves pacifier, rocks and soothes baby, provides four more pacifiers for good measure, stumbles back to bed.

11:00 Middle boy appears at parents' bedside: "It's too dark in my room. I'm afraid of monsters." Parent turns bathroom light on, lies down with middle boy until he is calm again, stumbles back to bed.

11:20 Middle boy is back. "It's still too dark in my room." Parent turns on hall light, lies down with middle boy, stumbles back to bed.

11:30 Middle boy is back again. "I'm thirsty." Parent fills sippy cup with water, hands it to boy, turns dining-room light on for good measure, stumbles back to bed.

1:45 Middle boy is back one more time. "I wet my bed." Both parents rise; one changes soggy bed, the other changes soggy boy. Oldest boy grumbles in his bed on the other side of the room, turns over, slams his pillow over his head. Parents stumble back to bed.

1:55 Oldest boy appears at parents' bedside. "I can't go back to sleep." Parent walks him back to his room, lies down with him, falls back into fitful sleep. Beside snoozing parent, oldest boy tosses restively.

3:30 Baby monitor sounds again. Remaining parent heads into nursery to retrieve all five missing pacifiers from behind crib, rocks angry baby till calm once more, retrieves missing co-parent from oldest son's bed, stumbles back to bed.

5:30 Parents' alarm clock sounds. Parents rise to begin effort of stumbling through another day.

As a point of honor, I ought to mention that the parent who's doing most of this rising during the night is not me. I get up with the children about twice for every five times my husband does. We arrived at this nighttime division of labor for the simple reason that my untroubled husband is capable of falling back to sleep instantly, no matter how many times he is awakened during a night.

But like my oldest son, after I'm rousted from a sound sleep, I'm wide awake for the next hour or two. Instead of drifting back to sleep, I fret: Did I offend my friend when I pointed out that her baby's car seat was too small for him now? Did I talk too much at that dinner party the other night? Am I paying my wonderful babysitter fairly? Is my former roommate going to be okay in her new Peace Corps assignment in Zimbabwe? Are there unlocked firearms in the house where my oldest son is going to play tomorrow afternoon?

So, though my husband does most of the kid-tending in the middle of the night, I'm the one who's lying in the dark wide awake after my turn at pacifier-fetching. If these researchers are right and eight hours of uninterrupted sleep is what's needed for new learning to enter long-term memory, it's no wonder I had to read the first three chapters of The Divine Secrets of the Ya-Ya Sisterhood seven times just to get all the characters' names straight. I haven't had eight hours of uninterrupted sleep since 1991. In the past nine years, I've missed roughly 6,572 hours of necessary slumber.

A year or so ago, I clipped out a magazine article titled "Pregnancy Changes Your Brain For The Better" about a study done by a couple of Virginia professors of neuroscience. In their research--which involved rats, not humans, it must be stated--high levels of pregnancy hormones increased the size of connections between the brain cells involved in communication and information transfer. In other words, the influx of pregnancy hormones enriched the parts of the brain involved in learning and memory. Female rats who had given birth learned to navigate mazes more quickly, and retained that learning longer, than rats who had not given birth. I saved the clipping because I thought it was sort of heartening news. I figured maybe I'd write a column about it.

But when I thought of myself and my pregnant friends, the Virginia rat research didn't seem to apply. I have one friend who left the house during her last pregnancy to take her dog for a walk. She got more than a block before noticing that she did have the leash but was missing the dog, and only then finally remembered that her dog had actually died the month before. Still, I thought, it might make an interesting column. But I lost the clipping. Then I forgot about the study.

And now I know why. Baby rats don't lose their pacifiers in the middle of the night. And mother rats don't lie in the dark and worry.

• Nashville Scene's Home Brood Archives
• Margaret Renkl Archives