Memory isn't 'lost,' just out of sync

May 09, 2002

(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.

JOHN HART, JR., M.D., is a graduate of The Johns Hopkins School of Medicine. He joined the UAMS College of Medicine faculty as an Associate Professor of Geriatrics last fall. Following medical school, 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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University of Arkansas for Medical Sciences

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