Sleep Affects Some Memories But Not All

Aug. 14 -- It's been a long, hard drive, and you finally arrive at your friend's home so dog tired all you want to do is sleep. But your friend is eager to fill you in on the latest gossip, and yaks for four or five hours until you fade out.

When you finally wake up, you're not sure where you are, and you can't even recall the location of the nearest bathroom. But you can remember some of those gossipy tidbits with absolute clarity, especially the scary story about Uncle Ed.

Why can you remember some things so clearly, and others not at all?

Because you store different types of memories in different areas of your brain, and those various areas are very selectively effected by the timing of your sleep deprivation, according to new research at the University of Pennsylvania. At least if you're a mouse, and probably if you're human.

Timing Is Everything

The research shows that mice deprived of sleep for about five hours immediately after learning their way around a frightening new environment have lost their memory of that "context" by the time they wake up. But they won't have any trouble recognizing a sound that tells them it's time to get the heck out of there.

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And that, according to assistant professor of biology Ted Abel, shows that sleep deprivation affects various memories stored in different neural systems, which are sort of like memory chips, in different parts of the brain. And the research shows that timing is everything.

"We were able to identify a particular type of memory that is susceptible to sleep deprivation," Abel says. We don't lose our ability to do everything when we need more sleep, as much of the current literature suggests, because some of our memories are more vulnerable to sleep deprivation than others, he says.

"People say sleep deprivation simply makes you unable to do everything," Abel says. "You can't hear sounds, you can't pay attention to driving or the environment. It's just a general loss of the ability to perform and respond to stimuli.