Feature Article
A Midday Nap Markedly Boosts the Brain's Learning Capacity
2010;18(4):12.
Findings suggest that a
biphasic sleep schedule not only refreshes the mind, but it can improve
neurocognitive functioning as well.
SAN DIEGO—An hour-long nap can dramatically boost
and restore your brain power, according to research presented at the
2010 Annual Meeting of the American Association for the Advancement of
Science.
Conversely, the more hours we spend awake, the more
sluggish our minds become, reported researchers from the University of
California, Berkeley. The results support previous findings from the
same research team that pulling an all-nighter—a common practice at
college during midterms and finals—decreases the ability to cram in new
facts by nearly 40%, due to a shutdown of brain regions during sleep
deprivation.
“Sleep not only rights the wrong of prolonged
wakefulness, but, at a neurocognitive level, it moves you beyond where
you were before you took a nap,” said lead investigator Matthew P.
Walker, PhD, Assistant Professor of Psychology and Neuroscience.
Sleep and Short-Term Memory Storage in the Brain
In the study, 39 healthy young adults were categorized into two groups—nap and no-nap. At noon, all participants were subjected to a rigorous learning task intended to tax the hippocampus. The groups performed at comparable levels.
In the study, 39 healthy young adults were categorized into two groups—nap and no-nap. At noon, all participants were subjected to a rigorous learning task intended to tax the hippocampus. The groups performed at comparable levels.
At 2 pm, the nap group slept for 90 minutes, while
the no-nap group stayed awake. Later that day, at 6 pm, participants
performed a new round of learning exercises. Those who remained awake
throughout the day became worse at learning. In contrast, those who
napped did markedly better and actually improved in their capacity to
learn.
These findings reinforce the researchers’ hypothesis
that sleep is needed to clear the brain’s short-term memory storage and
make room for new information, according to Dr. Walker.
Since 2007, Dr. Walker and other sleep researchers
have established that fact-based memories are temporarily stored in the
hippocampus before being sent to the brain’s prefrontal cortex, which
may have more storage space.
“It’s as though the e-mail inbox in your hippocampus
is full, and, until you sleep and clear out those fact e-mails, you’re
not going to receive any more mail. It’s just going to bounce until you
sleep and move it into another folder,” Dr. Walker said.
In their latest study, the researchers found that
this memory-refreshing process occurs when nappers are engaged in a
specific stage of sleep. EEG tests indicated that this refreshing of
memory capacity is related to stage 2 non–rapid eye movement (REM)
sleep, which takes place between deep sleep (non-REM) and the dream
state (REM). Previously, the purpose of this stage was unclear, but the
results offer evidence as to why humans spend at least half their
sleeping hours in stage 2, non-REM, according to Dr. Walker.
“I can’t imagine Mother Nature would have us spend
50% of the night going from one sleep stage to another for no reason,”
said Dr. Walker. “Sleep is sophisticated. It acts locally to give us
what we need.”
Dr. Walker and his team next want to investigate
whether the reduction of sleep experienced by people as they get older
is related to the documented decrease in our ability to learn as we age.
Finding that link may be helpful in understanding such
neurodegenerative conditions as Alzheimer’s disease, Dr. Walker
commented.
The Role of Sleep in Brain Development
In a separate study, Marcos Frank, PhD, Associate Professor of Neuroscience at the University of Pennsylvania School of Medicine in Philadelphia, presented information on early brain development and the importance of sleep during early life when the brain is rapidly maturing and highly changeable.
In a separate study, Marcos Frank, PhD, Associate Professor of Neuroscience at the University of Pennsylvania School of Medicine in Philadelphia, presented information on early brain development and the importance of sleep during early life when the brain is rapidly maturing and highly changeable.
Building on his research that the brain during sleep
is fundamentally different from the brain during wakefulness, Dr. Frank
found that cellular changes in the sleeping brain may promote the
formation of memories. “This is the first real direct insight into how
the brain, on a cellular level, changes the strength of its connections
during sleep,” said Dr. Frank.
For example, when an animal goes to sleep it’s like a
switch is thrown, and everything is turned on that’s necessary for
making synaptic changes that form the basis of memory formation, said
Dr. Frank.
He and his colleagues used an animal model of
cortical plasticity. They found that once the brain is triggered to
reorganize its neural networks in wakefulness (by visual deprivation,
for instance), intra- and intercellular communication pathways engage,
setting a series of enzymes into action within the reorganizing neurons
during sleep. The key cellular player in this process is the
N-methyl-d-aspartate receptor (NMDA), which acts like a combination
listening post and gate-keeper, noted Dr. Frank. It both receives
extracellular signals in the form of glutamate and regulates the flow of
calcium ions into cells.
“As soon as the animal had a chance to sleep, we saw all the machinery of memory start to engage,” commented Dr. Frank.
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