Alzheimer's, Dementia & Mental Health
Monitoring the Brain’s Memory-Making Cells
Exactly how memories are recorded and recalled
remains a mystery but they are often processed and retrieved by the
hippocampus
By Vicki Contie, National Institutes of Health
Sept.
22, 2008 - The brain cells that fire when a person watches a brief film
clip are triggered again when the person thinks back on that imagery a
few minutes later, a new study shows. The research offers insights into
how the brain summons up past experiences and may also provide clues to
brain disorders, like Alzheimer’s disease, that harm short-term memory.
Scientists have known for decades that memories are
often processed and retrieved by the hippocampus, a curved structure
deep in the brain. But exactly how memories are recorded and recalled
remains a mystery.
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Dr. Itzhak Fried, a professor of neurosurgery at
the University of California, Los Angeles, has been exploring the
mechanisms of memory at the single-neuron level in the human brain.
For the past 10 years, his research has focused on
patients with severe epilepsy who have many tiny electrodes implanted in
their brains. The electrodes are used to pinpoint seizure-causing brain
regions for surgical removal, but they can also provide information
about how individual brain cells process memories.
In his latest study, published in the online
edition of Science on September 4, 2008, Dr. Fried and colleagues at the
Weizmann Institute of Science in Israel monitored electrode recordings
of hundreds of neurons while patients watched a series of film clips and
then later recalled them.
Thirteen
patients participated in a total of 43 viewing and recall sessions. The
study was funded in part by NIH’s National Institute of Neurological
Disorders and Stroke (NINDS).
The patients were shown about a dozen brief clips,
each lasting about 5 to 10 seconds, of famous people, characters,
landmarks or activities. The clips included segments of TV shows like
The Simpsons and Seinfeld, portions of a speech by Martin Luther King,
the Golden Gate Bridge and the famous Hollywood sign. Each clip was
replayed a few times during each viewing session.
After viewing sessions, the patients engaged in a
different task for a few minutes. They were then asked to think about
the video clips they’d seen and say aloud which clips came to mind.
During the videos, more than half of the monitored
neurons had a significant response to one or more clips, and these
neurons became reactivated each time those clips were replayed. Later,
as the clips were remembered, the same neurons fired again.
In general, there was a 2-second lag between neuron
firing and verbal reporting of remembered clips.
For example, a neuron located near the hippocampus
in one patient showed a powerful response each time a clip from The
Simpsons appeared. It fired with less intensity when Seinfeld was shown
and remained essentially silent during 46 other clips.
When the patient later thought about the Simpsons
clip, the neuron fired for several seconds but had little or no response
to other memories. In all the patients, several neurons in and around
the hippocampus showed similar, selective responses to different film
clips.
It’s not clear exactly what aspects of the clips
triggered the cells’ responses. Nevertheless, this study adds to a
growing body of evidence that neurons in the brain’s memory centers can
play a dual role, responding first to sensory input and then
re-activating when that experience is later remembered.
More
About Memory at MedlinePlus
Your mind works a lot like a computer. Your brain
puts information it judges to be important into "files." When you
remember something, you pull up a file. Memory doesn't always work
perfectly. As people grow older, it may take longer to retrieve those
files. Some adults joke about having a "senior moment."
It's normal to forget things once in awhile. We've
all forgotten a name, where we put our keys, or if we locked the front
door. But forgetting how to use the telephone or find your way home may
be signs of a more serious problem. These include
Alzheimer's disease or other types of
dementia,
stroke, depression, head injuries, thyroid problems, or reactions to
certain medicines. If you're worried about your forgetfulness, see your
doctor.
More at
MedlinePlus
●
Forgetfulness: It's Not Always What You Think (National Institute on
Aging) - Also available in
Spanish
●
Memory Loss with Aging: What's Normal, What's Not (American Academy
of Family Physicians) - Also available in
Spanish
●
Understanding Memory Loss (National Institute on Aging) - Large PDF
file
● Memory:
http://www.nlm.nih.gov/medlineplus/memory.html
● Brain Basics:
Know Your Brain:
http://www.ninds.nih.gov/disorders/brain_basics/know_your_brain.htm
Related Topics at
MedlinePlus
●
Alzheimer's Disease
●
Dementia
●
Brain and Nerves
●
Mental Health and Behavior
●
Seniors
>>
National Institutes of Health
The primary NIH organization for research on Memory
is the
National Institute of Neurological Disorders and Stroke
