The role of sleep in memory: Research reports
What sleep does for memory
April 2009
Sleep may help clear the brain for new learning
Although fruit flies may seem little like us, their
response to sleep deprivation is similar, and so they are useful models for
sleep effects on the human brain. In a recent study, flies genetically altered
to make it easier to track individual synapses have revealed that during sleep
the number of new synapses formed during earlier learning decreased. This
decline didn’t happen if the flies were deprived of sleep. It’s theorised that
this activity during sleep is a way of pruning the less relevant and important
synapses (clearing away the junk, as it has been conceptualised). The study
follows earlier fruit fly research showing that more learning resulted in longer
sleep. It also supports recent rat research that found synaptic strength
increases during the day, then weakens during sleep. The study also identified
three genes essential to the links between learning and increased need for
sleep, one of which is equivalent to a human gene known as serum response factor
(SRF) and previously linked to brain plasticity.
The study was published in the April 3 edition of Science.
Full reference
http://www.eurekalert.org/pub_releases/2009-04/wuso-smh033109.php
http://www.eurekalert.org/pub_releases/2009-04/uow-ssc033009.php
November 2008
Sleep helps you learn complicated tasks & recover forgotten skills
A study involving 200 mostly female college students, who
had little experience of video games. The students were taught to play a
complicated, multisensory video game in which players must use both hands to
deal with continually changing visual and auditory signals. Half were tested 12
hours after the training session, and the others 24 hours later. Some were given
a night’s sleep before testing, others were tested the same day. Performance in
the former dropped by half at testing, but when tested again the following
morning, they showed a 10 percentage point improvement over their pre-test
performance. For those given evening training, scores improved by about 7
percentage points, then went to 10 percentage points the next morning – which
was maintained over the day. The findings indicate that although people may
appear to forget much of their learning over the course of a day, a night’s
sleep will restore it; moreover, sleep protected the memory from loss over the
course of the next day. The findings confirm the role of sleep in consolidating
memory for skills, and extends the research to complicated tasks.
The report appeared in the November issue of Learning and Memory.
Full reference
http://www.eurekalert.org/pub_releases/2008-11/uoc-shp111708.php
August 2008
Sleep selectively preserves emotional memories
It’s now generally accepted that sleep plays an important role in consolidating
procedural (skill) memories, but the position regarding other types of memory
has been less clear. A new study has found that sleep had an effect on
emotional aspects of a memory. The study involved showing 88 students neutral
scenes (such as a car parked on a street in front of shops) or negative scenes
(a badly crashed car parked on a similar street). They were then tested for
their memories of both the central objects in the pictures and the backgrounds
in the scenes, either after 12 daytime hours, or 12 night-time hours, or 30
minutes after viewing the images, in either the morning or evening. Those
tested after 12 daytime hours largely forgot the entire negative scene,
forgetting both the central objects and the backgrounds equally. But those
tested after a night’s sleep remembered the emotional item (e.g., the smashed
car) as well as those who were tested only 30 minutes later. Their memory of the
neutral background was however, as bad as the daytime group. The findings are
consistent with the view that the individual components of emotional memory
become 'unbound' during sleep, enabling the brain to selectively preserve only
that information it considers important.
The study was reported in the August issue of Psychological Science.
Full reference
http://www.physorg.com/news137908693.html
http://www.eurekalert.org/pub_releases/2008-08/bidm-sft081308.php
July 2008
Aging impairs the 'replay' of memories during sleep
During sleep, the hippocampus repeatedly "replays" brain activity from recent
experiences, in a process believed to be important for
memory consolidation. A
new rat study has found reduced replay activity during sleep in old compared to
young rats, and rats with the least replay activity performed the worst in tests
of spatial memory. The best old rats were also the ones that showed the best
sleep replay. Indeed, the animals who more faithfully replayed the sequence of
neural activity recorded during their earlier learning experience were the ones
who performed better on the spatial memory task, regardless of age. The replay
activity occurs during slow-wave sleep.
The research was reported in the July 30 issue of The Journal of Neuroscience.
Full reference
http://www.eurekalert.org/pub_releases/2008-07/sfn-ait072408.php
February 2008
A nap can help you learn
A study of 33 younger adults (average are 23) has found
that a 45 minute afternoon nap (containing only non-REM sleep) improved
performance on 3 different declarative memory tasks, but only when the subjects
had reached a certain level of performance during training.
The study was published in the February 1 issue of SLEEP.
Full reference
http://www.eurekalert.org/pub_releases/2008-02/aaos-jss012808.php
January 2008
Brain connections strengthen during waking hours, weaken during sleep
New research provides support for a much-debated theory that we need sleep to
give our synapses time to rest and recover. The human brain is said to expend up
to 80% of its energy on synaptic activity, constantly adding and strengthening
connections in response to stimulation. The researchers have theorized that we
need an ‘off-line period’, when we are not exposed to the environment, to take
synapses down. The rodent study has revealed by several measures that synapses —
the all-important points of connection between neurons — are very active when
the animal is awake and very quiet during sleep. The researchers feel that these
findings support the idea that our brain circuits get progressively stronger
during wakefulness and that sleep helps to recalibrate them to a sustainable
baseline. This theory is of course opposite to the currently dominant
hypothesis, that during sleep synapses are hard at work replaying the
information acquired during the previous waking hours, consolidating that
information by becoming even stronger.
The report appeared online January 20 in Nature Neuroscience.
Full reference
http://www.physorg.com/news120059987.html
April 2007
Sleep reinforces the temporal sequence in memory
Following on from research showing long-term memory is
consolidated during sleep through the replaying of recently encoded
experiences, a study has found that the particular order in which
they were experienced is also strengthened, probably by a replay of
the experiences in "forward" direction. The study involved students
being asked to learn triplets of words presented one after the
other. Those whose recall of the order of the words was tested after
sleep showed better recall, but only when they were asked to
reproduce the learned words in forward direction.
The paper appeared in the April 18 issue of
PLoS ONE.
Full reference
http://www.eurekalert.org/pub_releases/2007-04/plos-set041707.htm
Sleep protects against interference
A study involving 48 people (aged 18—30) found that those who
learned 20 pairs of words at 9pm and were tested at 9am the
following morning, after a night’s sleep, performed better than
those who learned them at 9am and were tested at 9pm of the same
day. Moreover, for those who were given a second list of word pairs
to remember just before testing, where the first word in each pair
was the same as on the earlier list, the advantage of sleep was
dramatically better. For those who experienced the interference
manipulation, those in the sleep group recalled 12% more word pairs
than the wake group, but with interference, the recall rate was 44%
higher for the sleep group.
The findings were presented by Dr Jeffrey Ellenbogen at the American
Academy of Neurology’s 59th Annual Meeting in Boston, April 28 – May
5, 2007.
http://www.eurekalert.org/pub_releases/2007-04/aaon-ssy040307.htm
Sleeping helps us put facts together
And in yet another sleep study, researchers found evidence that
sleep also helps us see the big picture. The study involved 56
students who were shown oval images of colorful abstract patterns
nicknamed "Fabergé eggs." Participants were first shown a
combination of five pairs of the eggs, all of which were given
ratings. The students were given 30 minutes to learn which shape
rated higher and so should be chosen over another shape. They were
not told the hidden connection that linked all five pairs together.
They were then tested either after 20 minutes, after 12 hours, or
after 24 hours. Half of those in the 12-hour group slept before the
test, the other half did not. The 20-minute group performed the
worst, showing no evidence of seeing the pattern. Those who had
longer before being tested were much more likely to show signs of
inferential judgment (75% vs 52%), and for the most distant (and
difficult) inferential judgment, the students who had had periods of
sleep in between learning and testing significantly outperformed
those who hadn’t slept (93% vs 69%). The researchers are interested
in exploring whether meditation can provide a similar benefit.
The findings appeared online April 20 in the Early Edition of the
Proceedings of the National Academy of Sciences.
Full
reference
http://www.physorg.com/news98376198.html
http://www.eurekalert.org/pub_releases/2007-04/bidm-tut042007.htm
More on how memories are consolidated during sleep
A new study sheds more light on how memory is consolidated during
sleep. Using a new technique, the research confirms that new
information is transferred between the
hippocampus
and the
cerebral cortex,
and, unexpectedly, provides evidence suggesting that the cerebral
cortex actively controls this transfer.
The study appeared in the November issue of
Nature Neuroscience.
Full
reference
http://www.eurekalert.org/pub_releases/2006-12/m-lds120506.htm
Still more on how memories are consolidated during sleep
In research following up an earlier study in which rats were
shown to form complex memories for sequences of events experienced
while they were awake, and that these memories were replayed while
they slept, it has been shown that these replayed memories do
contain the visual images that were present during the running
experience. By showing that the brain is replaying memory events in
the visual cortex and in the
hippocampus
at the same time, the finding suggests that this process may
contribute to or reflect the result of the memory consolidation
process.
The report appeared December 17 in the advance online edition of
Nature Neuroscience.
Full
reference
http://www.eurekalert.org/pub_releases/2006-12/miot-mtr121806.htm
October 2007
Brainwave oscillations responsible for memory benefits of sleep?
Passing a mild electrical current through the brain while
students were asleep improved their ability to remember words on
waking up. 13 medical students were given 46 pairs of words to
learn. Before sleeping, they remembered an average 37.42 words;
after sleep, those not given the stimulation remembered an average
of 39.5, while those given the stimulation remembered an average of
41.27. The memory enhancement only occurred at a certain frequency
and during a particular part of the sleep cycle, confirming the idea
that slow oscillations of electrical activity are responsible for
the memory consolidation effects of sleep. The benefit also only
applied to fact learning; skill learning was not affected.
The results were published online 5 November in
Nature.
Full
reference
http://www.guardian.co.uk/science/story/0,,1940475,00.html
http://www.sciam.com/article.cfm?chanID=sa003&articleID=BEC346B2-E7F2-99DF-350CC33BA6757700
http://www.nature.com/news/2006/061030/full/444133a.html
September 2006
More support that sleep helps consolidate learning
An experiment involving fruitflies has found that those in a
social environment with at least 30 other flies slept four times as
long during their daytime naps as flies in isolation. There was no
difference in night-time sleep. The length of the nap increased with
the size of the group they socialized with. Confirming that this
effect was due to an increase in social interactions, rather than,
for example, physical exhaustion from flying around more, flies
deprived of their sight and sense of smell (meaning they could still
fly around but could not socialize) showed no difference in daytime
sleep patterns. Of 49 genes known to be involved in learning and
memory, switching off seventeen (all related to long-term memory)
made the flies sleep equally long regardless of whether they were
social or not.
The study was reported in the September 22 issue of
Science.
Full
reference
http://www.nature.com/news/2006/060918/full/060918-9.html
http://www.livescience.com/humanbiology/060921_flies_sleep.html
Human study supports value of daytime napping for learning
REM sleep, when most dreaming occurs, has been shown in a number
of studies to be important in consolidating procedural (skill)
learning, while non-REM (slow-wave) sleep seems to be more important
for declarative (knowledge-based) learning. However, because normal
sleep contains both REM and non-REM cycles, research hasn’t been
able to clearly distinguish the effects. Now a new study using brief
daytime napping confirms the role of non-REM sleep for declarative
learning. Volunteers who memorized pairs of words and practiced
tracing images in a mirror test scored 15% better in the word test
if they had been allowed a nap in the six hour period before being
tested. However, they did no better at the action test.
The report appeared in the September issue of
Neurobiology of Learning and Memory.
Full
reference
http://www.newscientist.com/article/mg19125704.800?DCMP=NLC-nletter&nsref=mg19125704.800
July 2006
Sleep makes memories resistant to interference
It’s pretty clear now that sleep consolidates procedural (skill)
learning, but the question of whether or not it helps other types of
memory is still very much a matter of debate. However, a new study
has found a marked effect of sleep on our ability to remember
information. The study involved 60 healthy college-aged adults, who
were asked them to memorize 20 pairs of random words. Half were
given the words at 9am and tested at 9pm, and the other half were
given the words at 9pm and tested at 9am. While the sleepers did
perform better (94% recall compared to 82%), it was the introduction
of another factor that made the benefits of sleep undeniable.
Participants who were given a new set of words to learn just 12
minutes before testing revealed a dramatic difference — sleepers
recalled 76% of the original words compared to 32% of the sleepless.
The findings are reported in the July 12 issue of
Current Biology.
Full
reference
http://www.sciencedaily.com/releases/2006/07/060711095912.htm
http://www.sciam.com/article.cfm?chanID=sa003&articleID=0006A257-BBB4-14B2-B8B983414B7F4945
March 2006
Asleep or awake we retain memory
We’ve learned that skill memory is reinforced during sleep, but
now new imaging technology reveals that this kind of reinforcement
occurs while we’re awake too — even while we’re learning something
new.
The study was published in PLoS Biology.
Full
reference
http://www.eurekalert.org/pub_releases/2006-03/plos-aoa032206.htm
http://www.sciencedaily.com/releases/2006/03/060329085308.htm
June 2005
How sleep improves memory
While previous research has been conflicting, it does now seem
clear that sleep consolidates learning of motor skills in
particular. A new imaging study involving 12 young adults taught a
sequence of skilled finger movements has found a dramatic shift in
activity pattern when doing the task in those who were allowed to
sleep during the 12 hour period before testing. Increased activity
was found in the right primary motor cortex, medial prefrontal lobe,
hippocampus and left cerebellum — this is assumed to support faster
and more accurate motor output. Decreased activity was found in the
parietal cortices, the left insular cortex, temporal pole and
fronto-polar region — these are assumed to reflect less anxiety and
a reduced need for conscious spatial monitoring. It’s suggested that
this is one reason why infants need so much sleep — motor skill
learning is a high priority at this age. The findings may also have
implications for stroke patients and others who have suffered brain
injuries.
The findings were reported in the June 30 issue of
Neuroscience.
Full reference
http://www.eurekalert.org/pub_releases/2005-06/bidm-ssh062805.htm
October 2004
More evidence that learning is consolidated during sleep
A new study provides more evidence for the role of sleep in the
consolidation of long-term memories. In the study, volunteers
learned the layout of a virtual town, and were then tested by having
to quickly find routes to various locations in the town. Those so
trained showed greater activity in their
hippocampus and an adjacent learning-related region (compared to
those not trained) as they took the route tests, with greater
activity correlated with better performance. They also showed
greater hippocampal brain activity during sleep. Most importantly,
the higher the gain in post-sleep performance on the tests, the
higher had been their NREM brain activity during sleep. No such
correlation was found in REM brain activity. The findings support
the view that spatial memory traces are processed during NREM sleep
in humans.
The study appeared in the October 28 issue of
Neuron.
Full
reference
http://www.eurekalert.org/pub_releases/2004-10/cp-etl102204.htm
February 2004
Mentally, sleep may be as active a state as waking state
Why do we sleep? A question we keep asking. Recent research leads
us another step in the road. The study has identified a number of
genes upregulated specifically during sleep – at least as many as
are turned on while we are awake. These "sleep genes" largely fall
into four categories: genes involved in synaptic plasticity
(supporting the view that sleep aids memory consolidation); genes
underlying translation (supporting observations that protein
synthesis increases during sleep); genes regulating membrane and
vesicle trafficking; and genes for synthesizing cholesterol (which
may be crucial for synapse formation and maintenance, which could,
in turn, enhance neural plasticity (the brain's ability to change
and learn)). The study also found, to the researchers’ surprise,
that the cerebellum showed largely the same pattern of
gene-expression during sleep as the cortex.
The study was published in the January 8 issue of
Neuron.
Full
reference
http://www.the-scientist.com/yr2004/feb/research2_040216.html
More on what goes on during sleep
Brain activity patterns vary during sleep, with particular
distinction being made between “REM” sleep and “deep” sleep. Both
these phases of sleep have been associated with memory processing.
The chemical composition of the brain also varies a great deal in
the sleep and wakefulness cycle. New research from Germany now
report that some of these differences are crucial in memory
formation during sleep. In particular, the level of acetylcholine (a
neurotransmitter) is high during wakefulness and REM sleep but drops
to the minimum in deep sleep. In an experiment that involved
subjects performing two memory tasks – learning 40 pairs of
semantically related words, and learning to trace figures seen in a
mirror – before sleeping for four hours, it was found that those who
were given a cholinesterase inhibitor, (cholinesterase being an
enzyme that breaks down acetylcholine), performed significantly less
well in the wordlist task on wakening. The mirror-tracing task
didn't seem to be affected. This supports the idea that a low level
of acetylcholine is necessary for strengthening explicit memory
during deep sleep, and fits in with a proposed two-stage model of
long-term memory formation, in which the cortex transfers newly
acquired experiential data to the hippocampus for processing and
temporary storage (a process requiring high levels of
acetylcholine), and then, during sleep, the processed memory traces
in the hippocampus are relayed back to the cortex for long-term
storage. This feedback process is blocked by acetylcholine and,
thus, only happens in sleep when the acetylcholine level drops to
the minimum.
The research may also have important implications for treating
memory loss associated with Alzheimer's disease, as cholinesterase
inhibitors are widely used in such treatment. Because of common
side-effects of the drug, patients are usually told to take it at
night, which may well weaken the drug’s effectiveness.
The study was published in the February 17 issue of
Proceedings of National Academy of Sciences.
Full reference
http://gateways.bmn.com/neuroscience/news?uid=NEWS.040219-1
January 2004
Now definite? Memories are consolidated during sleep
Researchers of a new study claim that their research finally
settles the question of whether or not sleep consolidates new
memories. The study involved detailed recording of specific
learning- and memory- related areas (hippocampus
and
forebrain)
in the brains of rats. The rats were exposed to four kinds of novel
objects. Analysis of brain signals before, during, and after this
experience, revealed "reverberations" of distinctive brain wave
patterns across all the areas being monitored for up to 48 hours
after the novel experience. This pattern was much more prevalent in
slow-wave sleep than in REM sleep. Previous studies by the same
researchers have found that the activation of genes that affect
memory consolidation occurs during REM sleep, not slow-wave sleep.
It is proposed that both stages of sleep are important for memory
consolidation. Previous studies have tended to focus solely on the
hippocampus, and have observed brain activity for a much shorter
period.
The researchers published their findings on Jan. 19, 2004, in the
online Public Library of Science.
Full reference
http://www.eurekalert.org/pub_releases/2004-01/dumc-etm011304.htm
http://www.eurekalert.org/pub_releases/2004-01/plos-brd011204.htm
http://www.plosbiology.org/plosonline/?request=get-document&doi=10.1371/journal.pbio.0020037
Full text:
http://www.plosbiology.org/plosonline/?request=get-document&doi=10.1371%2Fjournal.pbio.0020024
Sleep helps insight
A new German study provides evidence for what we all suspected —
“sleeping on” a problem can really work. In the study, participants
were given a mathematical puzzle to solve; a puzzle which could be
solved by trial-by-trial learning, or almost immediately if
participants grasped the hidden rule. After training in the
trial-by-trial learning, some of the participants were allowed to
sleep through the night, while others were prevented from sleeping.
When they returned to the problem eight hours later, those that had
slept were twice as likely to realize the rule. Another group that
trained in the morning, and were then tested later that day, were
also slower at finding the rule, suggesting that the slowness was
not solely due to fatigue. Sleep did not, however, help participants
who had not had the initial training. It is suggested that sleep can
act to restructure new memory representations.
The study was published on 22 January in
Nature.
Full reference
http://www.sciam.com/article.cfm?chanID=sa003&articleID=000088CE-E9DC-100E-A9DC83414B7F0000
http://www.sfgate.com/cgi-bin/article.cgi?file=/news/archive/2004/01/21/national0259EST0431.DTL
http://www.nature.com/nsu/040119/040119-10.html
http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v427/n6972/abs/nature02223_fs.html
October 2003
Stages of memory clarified in sleep studies
Two new studies add to our understanding of the effects of sleep
on memory. Both studies involved young adults and procedural (skill)
learning, and found temporary declines in performance in particular
contexts (a brief description of these studies is given
here). On the basis of these studies, researchers identified
three stages of memory processing: the first stage of memory — its
stabilization — seems to take around six hours. During this period,
the memory appears particularly vulnerable to being “lost”. The
second stage of memory processing — consolidation — occurs during
sleep. The third and final stage is the recall phase, when the
memory is once again ready to be accessed and re-edited. (see my
article on consolidation for more explanation of the processes
of consolidation and re-consolidation). The surprising aspect to
this is the time it appears to take for memories to initially
stabilize. The studies also confirm the role of sleep in the
consolidation process.
The studies appeared in the October 9 issue of Nature.
Full
reference
2
http://www.eurekalert.org/pub_releases/2003-10/bidm-som100703.htm
http://www.sciencenews.org/20031011/fob4.asp
http://education.guardian.co.uk/higher/research/story/0,9865,1059138,00.html
July 2003
More support for the theory that sleep is necessary to consolidate memories
A study used fear conditioning in mice to investigate the effect
of sleep deprivation on memory. The mice were given a mild electric
shock either in a distinctive setting, or subsequent to a tone.
Those who experienced the tone continued to freeze when they heard
the tone on the following day, whether or not they had been deprived
of sleep. Those who associated the environment with the shock,
however, were less likely to freeze after sleep deprivation. Mice
who had been deprived of sleep during the five hours following
training, spent just 4% of their time frozen when returned to the
‘shock environment’ the following day, compared to 15% among mice
who were allowed to sleep during this period. The five hours
following training was a critical period – those who were deprived
of sleep in the 5-10 hours after training showed no sign of memory
impairment. The fact that the context association was affected but
not the tone cue, suggests that sleep is affecting processes in the
hippocampus (important in context memory but not memory for specific
facts or events).
The results were reported in the May/June issue of
Learning & Memory.
Full
reference
http://www.eurekalert.org/pub_releases/2003-07/uop-sdw070803.htm
June 2003
Another step in understanding how sleep affects memory
The value of sleep for memory takes a further step in being
understood in new rodent research, which found that, as the rodents
slept, the thalamus at the base of their brains originated bursts of
electrical activity (“sleep spindles”), which were then detected in
the somatosensory neocortex. Some 50 msec later, the hippocampus
responded with a pulse of electricity (a “ripple”). "This
neocortical-hippocampal dialogue may provide a selection mechanism
for the time-compressed replay of information learned during the
day." It’s suggested that the ripple is the hippocampus sending back
neat, compact waves of memory to the neocortex where they are filed
away for future reference. Most of this activity took place during
slow wave sleep, the stage which makes up the majority of the sleep
cycle.
The findings are reported in the June 6 issue of
Science.
Full
reference
http://www.eurekalert.org/pub_releases/2003-06/nyu-fir060503.htm
http://tinyurl.com/ftob
July 2002
Napping reverses information overload
Evidence is mounting that sleep helps information processing and
learning. A new study has showed that subjects performing a visual
task (reporting the horizontal or vertical orientation of three
diagonal bars against a background of horizontal bars in the corner
of a computer screen) got worse over the course of four daily
practice sessions. However, allowing subjects a 30-minute nap after
the second session prevented any further deterioration, and a 1-hour
nap actually boosted performance in the third and fourth sessions
back to morning levels. It appears that the fatigue is limited to
the brain visual system circuits involved in the task. When the
image was switched to a different right corner of the computer
screen on the fourth practice session, subjects performed about as
well as they did in the first session -- or after a short nap.
Recordings of brain activity reveal that the 1-hour naps contained
more than four times as much deep, or slow wave sleep and rapid eye
movement (REM) sleep than the half-hour naps.
The study was reported in the July 1 issue of
Nature Neuroscience.
Full reference
http://www.eurekalert.org/pub_releases/2002-07/niom-np070102.htm
Improving motor skills through sleep
People taught a simple motor sequence (to type a sequence of keys
on a computer keyboard as quickly and accurately as possible)
practised it for 12 minutes and were then re-tested 12 hours later.
Those who practised in the morning and tested later that same day
improved their performance by about 2%. Those trained in the evening
and re-tested after a good night's sleep, however, improved by about
20%. The amount of improvement was directly correlated with the
amount of Stage 2 (a stage of non-rapid eye movement or NREM) sleep
experienced, particularly late in the night. "This is the part of a
good night's sleep that many people will cut short by getting up
early in the morning."
The study appeared in the July 3 issue of
Neuron.
Full reference
http://www.eurekalert.org/pub_releases/2002-07/hms-pmp070102.htm
November 2001
Controversy over sleep's role in memory
Does sleep play a role in memory or not? Two new research papers
reach opposite conclusions. One is from Robert Stickgold, who has
published several papers supporting the role of sleep in memory
consolidation. But the other is a new review of REM sleep studies
concluding that REM (rapid eye movement) sleep, or dreaming, plays
little role in memory formation, chiefly on the basis that depriving
animals and humans of REM sleep by awakening them or by drug
treatments does not impair their ability to form long-term memories.
In addition, the time spent in REM sleep does not correlate with
learning ability across humans, nor is there a positive relation
between amount or intensity of REM sleep and learning ability across
species.
The articles appear in the November 2 edition of
Science. Full references
1,
2
http://www.sciencemag.org/cgi/content/abstract/294/5544/1052
http://www.sciencemag.org/cgi/content/abstract/294/5544/1058
October 2001
New motor skills consolidated during sleep
An imaging study that sheds light on the gain in performance
observed during the day after learning a new task. Following
training in a motor skill, certain brain areas appear to be
reactived during REM sleep, resulting in an optimization of the
network that subtends the subject's visuo–motor response.
The report appeared in the October issue of
Neuroscience.
Full reference
November 2000
Deep "slow wave" sleep necessary to consolidate memories
Sleep is necessary to consolidate memories. Remembering a new
task is more difficult if you don't sleep within 30 hours of
learning the task. "Catch-up" sleep on subsequent nights doesn't
make up for losing that first night's sleep. Moreover, it appears
that the deep "slow wave" sleep that occurs in the first half of the
night is the type of sleep necessary to consolidate memories. Other
types of memory however, may require "REM" sleep (that occurs while
you are dreaming).
The study was published in the December issue of
Nature Neuroscience.
http://www.independent.co.uk/story.jsp?story=6296
Stickgold, R., James, L. & Hobson, J.A. 2000. Visual discrimination learning requires sleep after training. Nature Neuroscience,3, 1237-1238.