Emotion
Affects Ability To Recall Events
Scientists Study
How Better Memories Are Made
When you remember
an emotional event, your memory of it may be very accurate,
but you are likely to forget the events that preceded it, researchers
report.
"If an emotional event
happens, you remember it better," says lead researcher Dr. Ray
Dolan, a professor of neurology at University College London.
However, this comes
at a cost, Dr. Dolan says. Things that precede the emotional
event tend to be remembered less well by those who have
experienced it.
Dr. Dolan and his
colleagues asked 10 volunteers to study a list of nouns. Each
list contained emotionally aversive words such as "murder" or
"scream." The subjects were then asked to recall the words on
the list.
The researchers found
the volunteers remembered the emotionally charged words much
better than the other words. In addition, they had significant
trouble remembering the words that came immediately before the
emotionally charged words.
They also found that
among women the effect of emotion-induced amnesia was twice
as great as compared with men, according to their report
in the Proceedings of the National Academy of Sciences.
To determine the neurological
basis for this finding, Dr. Dolan's team repeated the test with
24 subjects who were given either propranolol, a beta blocker
drug that can also reduce anxiety, or a placebo (an inactive
substance).
They also tried the
test on an individual who had damage to the part of the brain
called the amygdala. The amygdala is involved in producing and
responding to nonverbal signs of avoidance, defensiveness, and
fear.
The team found that
"by blocking the emotional arousal associated with these events
you can reverse the process," Dr. Dolan says.
Among the subjects
who received the drug and the subject with the damaged amygdala,
there was no improvement in the memory of the emotionally charged
words and no emotional amnesia for the words that came directly
before.
Dr. Dolan says the
implication of these findings is that witnesses to emotionally
charged events such as accidents or crimes may have totally
incorrect memories of what led up to the event. Therefore, their
accounts may be poor or unreliable.
Furthering their research,
Dr. Dolan's team continues to study how mechanisms of memory
can be disrupted. Their goal, Dr. Dolan says, is to determine
how better memories are created.
"The findings of this
study are important because they suggest that the brain mechanisms
that we think are important for enhanced memory associated with
emotional events are also involved in memory impairment for
emotional events," says Dr. Larry Cahill, an assistant professor
of neurobiology at the University of California at Irvine, and
author of an accompanying commentary.
"They may lead to
a better understanding of how emotion affects the mechanisms
of memory," he says.
Always consult your
physician for more information.
Anatomy
of the Brain
The brain can be divided
into the cerebrum, brainstem, and cerebellum:
cerebrum
The cerebrum (supratentorial or front of brain) is composed
of the right and left hemispheres. Functions of the cerebrum
include: initiation of movement, coordination of movement, temperature,
touch, vision, hearing, judgment, reasoning, problem solving,
emotions, and learning.
brainstem
The brainstem (midline or middle of brain) includes the midbrain,
the pons, and the medulla. Functions of this area include: movement
of the eyes and mouth, relaying sensory messages (hot, pain,
loud, etc.), hunger, respirations, consciousness, cardiac function,
body temperature, involuntary muscle movements, sneezing, coughing,
vomiting, and swallowing.
cerebellum
The cerebellum (infratentorial or back of brain) is
located at the back of the head. Its function is to coordinate
voluntary muscle movements and to maintain posture, balance,
and equilibrium.
More specifically,
other parts of the brain include the following:
pons
A deep part of the brain, located in the brainstem,
the pons contains many of the control areas for eye and face
movements.
medulla
The lowest part of the brainstem, the medulla is the
most vital part of the entire brain and contains important control
centers for the heart and lungs.
spinal cord
A large bundle of nerve fibers located in the back that extends
from the base of the brain to the lower back, the spinal cord
carries messages to and from the brain and the rest of the body.
frontal lobe
The largest section of the brain located in the front
of the head, the frontal lobe is involved in personality characteristics
and movement.
parietal lobe
The middle part of the brain, the parietal lobe helps
a person to identify objects and understand spatial relationships
(where one's body is compared to objects around the person).
The parietal lobe is also involved in interpreting pain and
touch in the body.
occipital
lobe
The occipital lobe is the back part of the brain that
is involved with vision.
temporal lobe
The sides of the brain, these temporal lobes are involved in
memory, speech, and sense of smell.
Online
Resources
(Our Organization
is not responsible for the content of Internet sites.)
Alzheimer's
Disease Association
American
Parkinson Disease Association
Centers
for Disease Control and Prevention (CDC)
Huntington's
Disease Society of America
National
Institutes of Health (NIH)
National
Institute of Mental Health
Science
of Emotion, National Institute of Mental Health
US
Department of Heath and Human Services
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December 2003
Emotion
Affects Ability To Recall Events
Anatomy
of the Brain
Experts
Study Neurons and How the Brain Adapts
Medical
Conditions and Neurons
Online
Resources
Experts
Study Neurons and How the Brain Adapts
A "reset switch" that
increases or decreases the sensitivity of brain cells to stimulation
by their neighbors has been identified by Duke University Medical
Center neurobiologists.
This action, called
homeostatic plasticity, enables the brain to adapt to changes
in the environment. It helps the brain avoid having its neurons
swamped by increased activity of the neural pathway or from
becoming too insensitive to detect triggering impulses from
other neurons when there is low neural activity.
Neurons are nerve
cells that act as information messengers between the different
areas of the brain and the brain and the rest of the nervous
system.
The Duke scientists,
reporting in the medical journal Neuron, used
an array of analytical techniques in their study. They say this
homeostatic plasticity is distinct from more rapid changes in
neural circuits that occur during the formation of memory.
The research offers
long-sought clues to how neurons protect themselves during stroke,
epilepsy, and spinal cord damage. The study may also help explain
various brain changes that occur during early childhood and
problems that occur later in life when people develop Alzheimer's
or Parkinson's disease.
"Neurobiologists have
understood that a neuron can increase only so much its firing
rate in response to inputs from other neurons, and then it saturates," says
lead researcher Dr. Michael Ehlers, an assistant professor of
neurobiology.
"There had to be a
way for a neuron to recalibrate - to scale up or down to stay
within an optimal dynamic firing frequency range," he says.
"Consider when you're
driving a car with a manual transmission," Dr. Ehlers says.
"As you accelerate, you reach a point where the engine's RPMs
are maximal and can go no higher. At that point, you need to
switch gears to bring back your RPMs to an optimal range.
"What we have found
is the molecular clutch that allows neurons to shift gears,"
Dr. Ehlers says. "This really is a profoundly important discovery.
Imagine if your brain could operate only in 'second gear."
Always consult your
physician for more information.
Medical
Conditions and Neurons
Neurons are the longest
living cells in the body. However, some diseases of the brain
are the result of the unnatural deaths of neurons.
According to the National
Institute of Neurological Disorders and Stroke:
-
In Parkinson’s disease, neurons
that produce the neurotransmitter dopamine die off in the basal
ganglia, an area of the brain that controls body movements. The
basal ganglia is a collection of thousands of neurons located
deep within the brain that controls voluntary body movement and
establishes postures. The brain can no longer control the body
and people shake and jerk in spasms.
-
In Huntington’s disease, a
genetic mutation causes over-production of a neurotransmitter
called glutamate, which kills neurons in the basal ganglia. As
a result, people twist and writhe uncontrollably.
-
In Alzheimer’s disease, unusual
proteins build up in and around neurons in the neocortex and hippocampus,
parts of the brain that control memory. When these neurons die,
people lose their capacity to remember and their ability to do
everyday tasks. Physical damage to the brain and other parts of
the central nervous system can also kill or disable neurons.
-
Blows to the brain, or the
damage caused by a stroke, can kill neurons outright or
slowly starve them of the oxygen and nutrients they need
to survive.
-
Spinal cord injury can disrupt
communication between the brain and muscles when neurons
lose their connection to axons located below the site
of injury. These neurons may still live, but they lose
their ability to communicate.
Always consult your
physician for more information.
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