05-09-02 (Little Rock) Findings published last week in Proceeding
of the National Academy of Science (USA) could lead to a better
understanding of how our memory changes with age, according to
John Hart, Jr., M.D. associate professor in the Reynolds Department of
Geriatrics of the UAMS College of Medicine and a co-author of the
study. "This new approach to looking at mechanisms of memory via
electrical rhythms raises a whole series of questions about how the
brain operates and what happens when it doesn’t work properly,"
he explained.
The study, conducted by Dr. Hart and
co-investigators Scott Slotnick, Ph.D., Lauren Moo, M.D., Michael
Kraut, M.D., Ph.D., and R. Lesser, M.D. of Johns Hopkins University,
involves a novel explanation for how we recall memories for objects
that surround us. The medical researchers suggest that objects occur
in your memory by uniting together the different brain regions that
make up various parts of the object you are trying to remember. For
example, the memory of a dog includes uniting smell, sound, appearance
and name.
By measuring the electrical rhythms
that parts of the brain use to communicate with each other, the team
of researchers showed that when the memory of a dog occurs, the
thalamus, an important region of the brain that connects areas
together, actually regulates the rhythms that connect brain regions.
"Memory appears to be a constructive process in combining the
features of the items to be remembered rather than simply remembering
each object as a whole form," Dr. Slotnick explained. "The
thalamus seems to direct or modulate the brain’s activity so that
the regions needed for memory are connected."
"It appears that the electrical
signals synchronize the brain regions that store each part of an
object’s memory so that those areas are connected," Dr. Hart,
the study’s senior author, continued. "This co-activation of
brain regions likely represents the memory of the object itself. It
may also explain why we may remember something clearly, and other
times we can only come up with parts of the item we are trying to
remember. Many times we say ‘you know, it has humps, it lives in the
desert ...’ This may occur when the rhythms don’t synchronize with
the regions properly. It could also explain why the memory will come
to you at a later time."
An important implication of the study’s
association of the thalamus and rhythms to memory is that patients,
including those who suffer from Alzheimer’s disease, who experience
this sort of memory loss may not actually be losing information.
Instead, the memory process is being disrupted.
Dr. Hart is establishing an imaging and
cognition research laboratory at the Donald W. Reynolds Center on
Aging at UAMS, where he and other researchers will use memory testing,
functional MRI, and measurement of the brain’s electrical activity
to develop diagnostic tools to identify people with memory disorders.
Such a facility may benefit not only Alzheimer’s patients, he said,
but it will also help stroke and head injury patients, as well as
those with schizophrenia.
"We want to try to figure out,
based on this approach to memory function, what sort of
neurotransmitters and brain regions are being disrupted during the
memory process. Then we want to see if we can treat patients by
regulating this disrupted memory circuit," Dr. Hart explained.
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BIOGRAPHICAL INFORMATION:
Dr. John Hart, Jr.
JOHN HART, JR., M.D., joined the UAMS
College of Medicine faculty as an Associate Professor of Geriatrics
last fall (2001). He is a graduate of The Johns Hopkins School of
Medicine. Dr. Hart also completed a residency in Neurology and a
fellowship in Cognitive Neurology and Neuropsychology at Johns
Hopkins. He was an Assistant Professor of Neurology and Cognitive
Science on the Johns Hopkins’ faculty, and a member of the Zanvyl
Krieger Mind/Brain Institute. He currently serves as
Secretary/Treasurer of the Behavioral Neurology Section of the
American Academy of Neurology. An active researcher, Dr. Hart has
published numerous articles in peer-reviewed journals. He has
contributed to a dozen textbooks and has presented his research
findings at meetings throughout the world. Dr. Hart has obtained
research funding from the National Institutes of Health and major
pharmaceutical companies.
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