like the corners of my mind...

Barbra sang about memories and how "what's too painful to remember we simply choose to forget." It seems that she wasn't too far off from how our memory works. Sometimes forgetting something can be a useful thing.

Whether drawing a mental blank on a new A.T.M. password, a favorite recipe or an old boyfriend, people have ample opportunity every day to curse their own forgetfulness. But forgetting is also a blessing, and researchers reported on Sunday that the ability to block certain memories reduces the demands on the brain when it is trying to recall something important.

The study, appearing in the journal Nature Neuroscience, is the first to record visual images of people’s brains as they suppress distracting memories. The more efficiently that study participants were tuning out irrelevant words during a word-memorization test, the sharper the drop in activity in areas of their brains involved in recollection. Accurate remembering became easier, in terms of the energy required.

Blocking out a distracting memory is something like ignoring an old (and perhaps distracting) acquaintance, experts say: it makes it that much harder to reconnect the next time around. But recent studies suggest that the brain plays favorites with memories in exactly this way, snubbing some to better capture others. A lightning memory, in short, is not so much a matter of capacity as it is of ruthless pruning — and the new study catches the trace of this process at it happens.

“We’ve argued for some time that forgetting is adaptive, that people actively inhibit some memories to facilitate mental focus,” as when they are trying to recall a friend’s new phone number or the location of a parking space, said Michael Anderson, a professor of cognitive neuroscience at the University of Oregon.

Dr. Anderson, who was not involved in the new research, said it was "important new work because it maps out how this is happening neurobiologically.”

But what about when you get older, and you can't remember where the keys are?

The findings should also reduce some of the anxiety surrounding “senior moments,” researchers say. Some names, numbers and details are hard to retrieve not because memory is faltering, but because it is functioning just as it should.

Ah, good to know. Of course, those senior moments are sometimes an indication of something more insidious at work.