News reports of research into memory November 2001
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November 2001
On four occasions, a small group of older
people ( 61–79years) were given, after the night's fast, either
a drink containing protein (whey), carbohydrate (glucose), fat
(safflower oil), or a placebo. Cognitive tests were given 15 and
60 minutes later. Only the carbohydrate drink increased blood
glucose levels, but all 3 of the energy drinks improved memory
for paragraphs. Other memory improvements were specific to the
type of drink. For example, fat was the only one that enhanced
attention. In general, improvement was greater 60 minutes after
drinking than 15 minutes after.
The report appeared in the American Journal of Clinical
Nutrition. Full
reference
http://www.eurekalert.org/pub_releases/2001-10/ajoc-ecr101901.php
Scientists at the University of California, San Diego have
produced dramatic
images of brain cells forming temporary and permanent
connections in response to various stimuli, illustrating for the
first time the structural changes between neurons in the brain
that, many scientists have long believed, take place when we
store short-term and long-term memories.
The report appears in the 30 November issue of
Cell.
Full reference
http://ucsdnews.ucsd.edu/newsrel/science/mccell.htm
Failure to remember experiences often
occurs not because the memory is hard to retrieve, but because
it was not properly encoded in the first place. Imaging studies
are beginning to give us a better idea of the neurocognitive
processes that lead to more effective encoding.
The report appears in the November issue of
Current Biology.
Full reference
http://tinyurl.com/i87x
Learning and memory in humans rely upon
several memory systems. For example, the medial temporal lobe
(MTL) is associated with declarative learning (facts and
events). The basal ganglia is associated with nondeclarative
learning (learning you derive from experience, that may not be
conscious). A recent imaging study looked at how these memory
systems interact during classification learning. During the
nondeclarative learning task, there was an increase in activity
in the basal ganglia, and a decrease in activity in the MTL.
During the memorization task (testing declarative learning), the
reverse was true. Further examination found rapid modulation of
activity in these regions at the beginning of learning,
suggesting that subjects relied upon the medial temporal lobe
early in learning. However, this dependence rapidly declined
with training.
The report appeared in the 29 November issue of
Nature.
Full reference
http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v414/n6863/abs/414546a0_fs.html
http://www.eurekalert.org/pub_releases/2001-11/mgh-isi112601.php
Postmenopausal women who take estrogen
and young college-aged women performed more consistently on
memory tests compared with postmenopausal women not taking the
hormone. Consistency differs from overall memory ability and is
a relatively new area in research about the neuropsychology of
aging. Consistency measures memory capability on multiple
administrations of the same test or on several related tests in
a short period of time.
The study involved 48 postmenopausal women (aged 60 - 80), and
16 younger women (18 - 30). The older women were divided into
three groups: 16 non-hormone users, 16 estrogen-users and 16
estrogen and progesterone-users. Younger women and older women
taking estrogen performed more consistently than the older women
not taking the hormone, as well as having higher overall memory
scores. Women taking a combination of estrogen and progesterone
did not perform as consistently as the estrogen-only users. This
finding suggests progesterone may block some of the beneficial
effects of taking estrogen alone.
The study results were presented by Dr Wegesin on Sunday, Nov.
11 at the Society for Neuroscience meeting in San Diego.
Reference
http://www.eurekalert.org/pub_releases/2001-11/cuco-ssp111501.php
Lobectomy
patients were compared to normal control subjects on a variety
of category naming and matching tasks. Patients were
disproportionately impaired for naming living things relative to
nonliving things. The authors argue that damage to the temporal
lobe impairs lexical retrieval most strongly for living things
and that the anterior temporal cortices are convergence zones
particularly necessary for retrieving the names of living
things.
The report appeared in the November issue of
Brain and Language.
Full reference
Learning happens when a brain cell gets
stimulated in a way that reduces its ability to respond to a
particular brain messenger called glutamate. In the cerebellum
there are very large, strangely shaped brain cells called
Purkinje cells that receive more connections than other types of
neurons and fire 50 times per second even when you're sleeping.
These cells are involved in simple motor learning processes. A
recent study provides support for an earlier study that found
there are fewer receptors for glutamate on the surface of
neurons during long-term synaptic depression, by demonstrating
that the other three possible causes for this reduced response
to glutamate do not occur.
The report appeared in the November 20 issue of the
Proceedings of the National Academy of Sciences.
Full reference
A recent study has found that women have
up to 15% more brain cell density in the frontal lobe, which
controls so-called higher mental processes, such as judgement,
personality, planning and working memory. However, as they get
older, women appear to shed cells more rapidly from this area
than men. By old age, the density is similar for both sexes. It
is not yet clear what impact, if any, this difference has on
performance.
The findings were presented by Dr Witelson to the annual Society
for Neuroscience meeting in San Diego, US.
Reference
http://news.bbc.co.uk/hi/english/health/newsid_1653000/1653687.stm
Many of the cognitive deficits associated with advancing
age are related to functions of the prefrontal cortex such
as working memory, decision-making, planning and judgement.
Postmortem examination of 20 brains ranging in age from 25 to 83
years, confirm that prefrontal regions may be particularly
sensitive to the effects of aging. It also appears that white
matter decreases at a faster rate than grey matter with age.
The findings were presented to the annual Society for
Neuroscience meeting in San Diego, US.
Reference
It appears that cholesterol
stimulates the nerve cells of the brain to make the connections
that are essential to learning and memory, thus playing a
crucial role in making sure that the brain works properly. But
how does cholesterol do its job? The blood-brain barrier
prevents the brain obtaining cholesterol from the blood. New
research suggests that cholesterol is secreted by support cells
(glial cells) within the brain. The research may lead to new
strategies to cure injury- or disease-induced brain lesions, and
suggests a new hypothesis concerning Alzheimer's disease.
The report appeared in the November 9 issue ofScience.
Full reference
http://news.bbc.co.uk/hi/english/health/newsid_1645000/1645372.stm
http://www.eurekalert.org/pub_releases/2001-11/m-brd110401.php
It appears that exposure to polychlorinated biphenyls (PCBs)
in a mother's blood and breast milk can hinder the development
of a baby's brain before and after birth. Although PCBs are now
banned, these chemicals were once widely used in industry as
coolants and lubricants and are still being leaked into the
environment from old electrical equipment.
The report appeared in a recent issue of
The Lancet.
Full reference
http://news.bbc.co.uk/hi/english/health/newsid_1644000/1644446.stm
Patients with semantic impairments
sometimes demonstrate category-specific deficits suggesting that
the anatomical substrates of semantic memory may reflect
categorical organisation, however, neuroimaging studies have
failed to provide consistent data in support of a category-based
account. A further three studies have also failed to find robust
evidence of functional segregation by domain or categories. It's
argued that these results are most consistent with a semantic
system undifferentiated by category at the neural level.
The report appeared in the November issue of
Neuropsychologia.
Full reference
http://tinyurl.com/i87u
Encoding and recognition of unfamiliar faces
in young adults were examined using PET imaging to determine
whether different encoding strategies would lead to differences
in brain activity. It was found that encoding activated a
primarily ventral system including bilateral temporal and
fusiform regions and left prefrontal cortices, whereas
recognition activated a primarily dorsal set of regions
including right prefrontal and parietal areas. The type of
encoding strategy produced different brain activity patterns.
There was no effect of encoding strategy on brain activity
during recognition. The left inferior prefrontal cortex was
engaged during encoding regardless of strategy.
The report appeared in the November issue of
Neuropsychologia.
Full
reference
http://tinyurl.com/i87v
Children aged 4 to 7 were found to be
able to use both configural and featural information to
recognise faces. However, even when trained to proficiency on
recognising the target faces, their recognition was impaired
when a superfluous hat was added to the face.
The report appeared in the Journal of
Experimental Child Psychology.
Full reference
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 Nov. 2 edition of the peer-reviewed
journal Science. Full references
1,
2
http://news.bmn.com/news/story?day=011102&story=1
http://www.sciencemag.org/cgi/content/abstract/294/5544/1052
http://www.sciencemag.org/cgi/content/abstract/294/5544/1058
Why is it that people cannot keep their hands still when they
talk? One reason may be that gesturing
actually lightens cognitive load while a person is thinking of
what to say. Adults and children were asked to remember a list
of letters or words while explaining how they solved a math
problem. Both groups remembered significantly more items when
they gestured during their math explanations than when they did
not gesture.
The report appeared in Psychological
Science.
Full reference
Lesions in the medial temporal lobe (MTL)
typically produce amnesia characterized by the disproportionate
loss of recently acquired memories. Such memory loss has been
interpreted as evidence for a memory consolidation process
guided by the MTL. A recent imaging study confirms this view by
showing temporally graded changes in MTL activity in healthy
older adults taking a famous faces remote memory test. Evidence
for such temporally graded change in the hippocampal formation
was mixed, suggesting it may participate only in consolidation
processes lasting a few years. The entorhinal cortex (also part
of the MTL) was associated with temporally graded changes
extending up to 20 years, suggesting that it is the entorhinal
cortex, rather than the hippocampal formation, that participates
in memory consolidation over decades. The entorhinal cortex is
damaged in the early stages of Alzheimer’s disease (AD).
The report appeared in Nature
neuroscience.
Full reference
http://www.nature.com/neurolink/v4/n11/abs/nn739.html
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