University of Virginia Health System

Mind & Body

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

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.