Before a big exam, a sound night’s sleep will do you more good
than poring over textbooks. That, at least, is the folk wisdom. And science, in
the form of behavioral psychology, supports that wisdom. But such behavioral
studies cannot distinguish between two competing theories of why sleep is good
for the memory. one says that sleep is when permanent memories form. The other
says that they are actually formed during the day, but then "edited" at night,
to flush away what is superfluous. To tell the difference, it is
necessary to look into the brain of a sleeping person, and that is hard. But
after a decade of painstaking work, a team led by Pierre Maquet at Liege
University in Belgium has managed to do it. The particular stage of sleep in
which the Belgian group is interested in is rapid eye movement (REM) sleep, when
brain and body are active, heart rate and blood pressure increase, the eyes move
back and forth behind the eyelids as if watching a movie, and brainwave traces
resemble those of wakefulness. It is during this period of deep that people are
most likely to relive events of the previous day in dreams. Dr.
Maquet used an electronic device called PET to study the brains of people as
they practiced a task during the day, and as they slept during the following
night. The task required them to press a button as fast as possible, in response
to a light coming on in one of six positions. As they learnt how to do this,
their response times got faster. What they did not know was that the appearance
of the lights sometimes followed a pattern--what is referred to as "artificial
grammar". Yet the reductions in response time showed that they learnt faster
when the pattern was present than when there was not. What is
more, those with more to learn (i. e. , the "grammar", as well as the mechanical
task of pushing the button) have more active brains. The "editing" theory would
not predict that, since the number of irrelevant stimuli would be the same in
each case. And to eliminate any doubts that the experimental subjects were
learning as opposed to unlearning, their response times when they woke up were
even quicker than when they went to sleep. The team, therefore,
concluded that the nerve connections involved in memory are reinforced through
reactivation during REM sleep, particularly if the brain detects an inherent
structure in the material being learnt. So now, on the eve of that crucial test,
maths students can sleep soundly in the knowledge that what they will remember
the next day are the basic rules of algebra and not the incoherent talk from the
radio next door. Researchers in behavioral psychology are divided with regard to ______