Researchers have
uncovered new evidence that sleep improves the brain's
ability to remember information. Their findings demonstrate
that memories of recently learned word pairs are improved
if sleep intervenes between learning and testing and
that this benefit is most pronounced when memory is
challenged by competing information. The findings
are reported in the July 12th issue of Current Biology
by Jeffrey Ellenbogen, of Harvard Medical School,
and his colleagues.
Whether sleep facilitates memory
consolidation is a question as old as the experimental
study of memory itself. In recent years, there has
been a resurgence of experiments exploring this relationship.
Although there is near-consensus that sleep promotes
learning of certain types of perceptual memories (for
example, learning to tap numeric sequences on a keyboard),
there is ongoing debate about whether sleep benefits
so-called declarative memory, a key type of memory
that is based in the brain's hippocampus.
In the new work, the researchers
studied the influence of sleep on declarative memory
in healthy, college-aged adults. The results demonstrated
a robust effect: Compared to participants who did
not sleep during the trials, those who slept between
learning and testing were able to recall more of the
original words they had learned earlier. The beneficial
influence of sleep was particularly marked when participants
were presented with the challenge of "interference"--competing
word-pair information--just prior to testing. A follow-up
group further demonstrated that this sleep benefit
for memory persists over the subsequent waking day.
This work clarifies and extends previous study of
sleep and memory by demonstrating that sleep does
not just passively and transiently protect memories;
rather, sleep plays an active role in memory consolidation.
The researchers include Jeffrey
M. Ellenbogen of Harvard Medical School in Boston,
MA; Robert Stickgold of Harvard Medical School and
Beth-Israel Deaconess Medical Center in Boston, MA;
Justin C. Hulbert of the University of Oregon in Eugene,
OR; David F. Dinges and Sharon L. Thompson-Schill
of the University of Pennsylvania in Philadelphia,
PA.
This work was supported by the
University of Pennsylvania's Nassau Undergraduate
Research Fund (J.C.H.) and by the National Institutes
of Health.
