News reports of research into memory May 2003
For index of all headlines, go to News & Views main page
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You can find links to the journals referred to on this site here: Journal links
May 2003
For women over 65, Combined Hormone Therapy increases risk of dementia
Much to the researchers’ surprise and disappointment, a four-year
experiment involving 4,532 women at 39 medical centers, has found
that combined hormone therapy (involving both estrogen and
progestin) doubles the risk of Alzheimer's disease and other types
of dementia in women who began the treatment at age 65 or older,
although the risk is still small : for every 10,000 women 65 and
older who take hormones, 23 of the predicted 45 cases of dementia a
year, will be attributable to the hormones. The study also found
that the combined hormone therapy produced no improvement in general
cognitive function, and in fact had adverse effects on cognition
among some women. This supports an earlier study suggesting that,
while estrogen is helpful to cognitive function in postmenopausal
women, the benefits can be cancelled out by progestin /
progesterone. The study also confirmed previous research showing
that the combination therapy increased the risk of stroke - previous
research has indicated that risk factors for stroke are also risk
factors for cognitive decline.
The study was published in the May 28 issue of the
Journal of the American Medical Association.
Full reference 2
3
http://www.eurekalert.org/pub_releases/2003-05/wfub-chr052203.php
Cholesterol not a risk factor for Alzheimer's
Previously, the long-running, large-scale Framingham study found
people with elevated levels of homocysteine in the blood had nearly
double the risk of developing Alzheimer’s disease (AD). The study
now clarifies the inconclusive results from previous studies
regarding whether plasma cholesterol levels are associated with
increased risk ofAlzheimer disease (AD). They found that, after
adjustment for age, sex, APOE
genotype,smoking, body mass index, coronary heart disease,and
diabetes, there was no significant association between ADrisk and
cholesterol level.
The study was reported in the May 12 issue of the
Archives of Internal Medicine.
Full reference
http://archinte.ama-assn.org/cgi/content/abstract/163/9/1053
Treatment to lower blood pressure reduces risk of cognitive decline in stroke patients
High blood pressure and stroke are associated with increased risks
of dementia and cognitive impairment. In a study aimed to determine
whether blood pressure lowering would reduce the risks of dementia
and cognitive decline among individuals with cerebrovascular disease,
6105 people with prior stroke or transient ischemic attack were given
either active treatment (perindopril for all participants and indapamide
for those with neither an indication for nor a contraindicationto a
diuretic) or matching placebo(s). Over some 4 years, dementia was
found in 6.3% of those given active treatment and 7.1% of those in
the placebo group. Cognitive decline occurred in 9.1% of the actively
treated group and 11.0%of the placebo group. The researchers
concluded that blood pressure lowering with perindopril and
indapamide therapy was helpful for those with cerebrovascular
disease, in terms of reduced risks of dementia and cognitive decline.
The study was published in the May 12 issue of the
Archives of Internal Medicine.
Full reference
http://archinte.ama-assn.org/cgi/content/abstract/163/9/1069
Cognitive decline after bypass surgery appears more transient than feared
Recent studies have found a high occurrence of cognitive problems in patients
who undergo coronary artery bypass surgery, with such problems still found six
weeks after surgery. In a new study comparing 140 patients who underwent bypass
surgery and a second group of 92 coronary artery disease patients who did not
have surgery, no differences in cognitive abilities were found when patients
were re-tested at three and 12 months. This supports recent research suggesting
that it is the the disease itself that is the major problem, rather than the
surgery.
The report appeared in the May issue of The Annals of
Thoracic Surgery.
Full reference
http://www.newswise.com/articles/2003/5/COGNTIVE.JHM.html
http://www.eurekalert.org/pub_releases/2003-05/jhmi-gn050603.php
Poorly controlled diabetes could lead to dementia in the elderly
It now appears that the reason why diabetic people age 60 and
older tend to perform more poorly on cognitive tests is because of
improper management of their disease. A recent study evaluated the
association between diabetes mellitus status and cognitive function
in 2,583 adults aged 60 and older, grouping participants according
to their diabetic status (poorly controlled diabetes; adequately
controlled diabetes; those with impaired glucose tolerance; and a
non-diabetic control group). Cognitive ability was measured by a
series of simple memory questions. Only those with poorly controlled
diabetes performed poorly on the cognitive test.
The researchers presented their findings in April at the American
Academy of Neurology conference in Honolulu.
http://www.eurekalert.org/pub_releases/2003-05/osu-pcd050503.php
Fetuses recognize mother's voice in the womb
A study of 60 third-term fetuses found that they could
distinguish between their mother’s voice and the voice of a
stranger, as measured by changes in heart rate. Previous research
has shown that newborns prefer their own mother's voice to that of a
female stranger, but this demonstrates that this preference and
recognition begins in the womb.
The report was published in the May issue of
Psychological Science.
Full reference
http://qnc.queensu.ca/story_loader.htm?id=3ebc016fcd1ec
Imaging study confirms theory of dyslexia
Functional magnetic resonance imaging (fMRI) has confirmed part
of an eighty-year-old theory on the neurobiological basis of
dyslexia. Dr Orton theorized that normally developing readers learn
to suppress the visual images reported by the right hemisphere of
the brain because these images potentially interfere with input from
the left. The imaging study found that children do in fact "turn
off" the right side of the visual parts of the brain as they become
accomplished readers, and also demonstrated that different
phonological skills relate to activity in different parts of the
brain when children read. This observation lends support to the
theory that there may be several neurobiological profiles that
correspond to different subtypes of dyslexia, each associated with
varying deficits in one or more of these different phonological
skills.
The findings were published online on May 18 in
Nature Neuroscience.
Full reference
http://www.eurekalert.org/pub_releases/2003-05/gumc-wor051603.php
Impact of prenatal environment on learning abilities
In a fascinating study that points to the importance of
environment (including prenatal environment) in determining
behavioral and cognitive abilities, embryos from mice with a low
response to stress were transferred to high-stress surrogate mice.
The two strains of mice differed not only in their response to
stress but also in their learning abilities. At birth, the mice were
cross-fostered again and reared by either a low-stress mother or a
high-stress mother. The mice were tested at three months, and
researchers found that the low-stress mice that were transferred as
embryos to and also later reared by high-stress females were less
likely to explore new environments than those carried and reared by
low-stress mothers. The low-stress mice reared by high-stress
surrogates also performed more poorly on cognitive tests of their
ability to navigate mazes.
The finding was reported in the May issue of
Nature Neuroscience.
Full reference
http://www.eurekalert.org/pub_releases/2003-05/euhs-ees051203.php
Amphetamine helps or hinders cognitive function depending on your genes
Everyone inherits two copies of the catecho-O-methyltransferase
(COMT) gene, that codes for the enzyme that metabolizes
neurotransmitters like dopamine and norepinephrine. It comes in two
common versions. One version, met, contains the amino acid
methionine at a point in its chemical sequence where the other
version, val, contains a valine. Depending on the mix of variants
inherited, a person's COMT genes can be typed met/met, val/val, or
val/met. People with the val/val variant appear to have reduced
prefrontal dopamine activity and less efficient prefrontal
information processing, along with slightly increased risk for
schizophrenia. People with val/met have more efficient prefrontal
function, and people with met/met the most efficient.
In a recent imaging study, 27 volunteers (10 val/val, 11 val/met,
and 6 met/met) performed a variety of cognitive tasks that involved
working memory and executive functioning, after taking either
amphetamine or a placebo. Since amphetamine boosts dopamine activity
in the prefrontal cortex, the researchers predicted that the drug
would enable val/val types to boost their low level of dopamine and
perform better on cognitive tasks that depend on the prefrontal
cortex. On the other hand, those with met/met should be hindered by
amphetamine. The study confirmed these predictions - val/val
subjects on amphetamine performed comparably to met/met types in
normal conditions, while met/met subjects on amphetamine performed
worse than subjects with val/val types in normal conditions.
Amphetamines and other drugs that affect prefrontal dopamine systems
are used to treat Attention Deficit Hyperactivity Disorder (ADHD),
and other psychiatric illnesses, and some people respond better than
others to these medications. About 15-20% of individuals in
populations of European ancestry have the met/met COMT gene type.
The study was reported in the May 13 issue of
Proceedings of the National Academy of Sciences.
Full reference
http://www.eurekalert.org/pub_releases/2003-05/niom-gep050703.php
Rat study offers more complex model of brain aging
A study of young, middle-aged, and aged rats, trained on two
memory tasks, has revealed 146 genes connected with brain aging and
cognitive impairment. Importantly, the changes in gene activity had
mostly begun in mid-life, suggesting that changes in gene activity
in the brain in early adulthood might set off cellular or biological
changes that could affect how the brain works later in life. The
study provides more information on genes already linked to aging,
including some involved in inflammation and oxidative stress, and
also describes additional areas in which gene activity might play a
role in brain aging, including declines in energy metabolism in
cells and changes in the activity of neurons (nerve cells) in the
brain and their ability to make new connections with each other,
increases in cellular calcium levels which could trigger cell death,
cholesterol synthesis, iron metabolism and the breakdown of the
insulating myelin sheaths that when intact facilitate efficient
communication among neurons.
The report appeared in the May 2003 issue of
The Journal of Neuroscience.
Full reference
http://www.eurekalert.org/pub_releases/2003-05/nioa-nsi050203.php
Is a dwindling brain chemical responsible for age-related cognitive decline?
A study of what are probably the world's oldest monkeys may
explain age-related mental decline. The study found that the very
old monkeys' nerves in the visual cortex lose their ability to
discriminate between one signal and another and that this loss was
directly related to the presence of a chemical called
gamma-aminobutyric acid (Gaba), a neurotransmitter that appears to
dwindle in old age. If a lack of GABA is indeed responsible for the
old neurons' indiscriminate firing, this problem may be simple
enough to treat. There already exist drugs that increase GABA
production, although these drugs have yet to be carefully tested on
the elderly.
The study was reported in the May 2 issue of
Science.
Full reference
http://www.eurekalert.org/pub_releases/2003-05/aaft-sow042403.php
http://www.newswise.com/articles/2003/5/OLDBRAIN.UUT.html
http://www.utah.edu/unews/releases/03/may/oldbrain.html
http://news.independent.co.uk/world/science_medical/story.jsp?story=402317
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