Caught in a Maze

DREAMS

Like it or not, humans aren't so different from rats--at least when
it comes to the basic functioning of the brain. It's a good thing,
actually, because recent research performed on rats might help people
better understand what's going on with the human brain when they
sleep.

Rats appear to dream, and researchers at the Massachusetts
Institute of Technology (MIT) have discovered what their furry subjects
are dreaming about: the mazes they seem to be learning to run. These
nocturnal thoughts offer insight into the relationship between sleep and
memory.

What happens in a rat's brain during sleep sometimes mimics what
happened during the day. The highly specific patterns of neurons fired in
the rats' brains while running a lab maze appeared again during rapid eye
movement (REM) sleep, indicating that the rats were reactivating a
learned experience while sleeping. "We can pinpoint exactly where they
would be on the maze if they were awake," explains lead researcher
Matthew Wilson, Ph.D., an associate professor at MIT, whose latest
findings were published in the journal Neuron.

The dreams of these rats, though, might be more than simply a
replaying of a day's events, the MIT researchers say. "We believe that
recalling specific episodes of waking life during sleep is actually a
process of reevaluation," says Wilson.

That means that not only are the rats remembering each specific
turn of the maze, but they may be trying to figure out how to perform
better next time. And, since rat brains are structured just like human
brains--only more simply--people, too, probably reevaluate memories
during sleep. The complex, metaphorical nature of dreams may be due to
the far more complicated human brain and richer human experience. Wilson
points out that studies have suggested that sleep can help people solve
specific problems, but it was unclear whether this was simply due to the
biochemical value of rest. The rat research supports the idea that there
is more going on during sleep than rest. "Sleep is the period in which
the brain is able to operate without the need to respond to the outside
world," Wilson says.

He and his colleagues are still working with the rats to determine
whether replaying memories in dreams actually does impact performance,
but one thing seems certain: Daytime activities do appear in dreams. In
humans, it's possible that many experiences come together to form the
sort of strange scenarios many people remember from their dreams.
"Recombining memories helps us make sense of the world, and it seems that
this happens during REM sleep" Wilson says.

Thanks to the maze-running rats, more doors are opening into the
recesses of the human brain.

ILLUSTRATION (BLACK & WHITE)