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Alzheimer's, Dementia & Mental Health
Lack of Recall of Current Data, Good Recall of Long
Ago May Mean Too Much Memory
New research finds that too much memory may be a
bad thing
 March 29, 2007 – You cannot recall today's date,
but you do remember the date you first learned to ride a bicycle back in
the 1940s. Oh no, you think, dementia is setting in. That may not be the
case. New research says people having trouble taking in new information,
while retaining old useless information may have too much memory.
This new research from Columbia University Medical
Center may explain why people who are able to easily and accurately
recall historical dates or long-ago events, may have a harder time with
word recall or remembering the day’s current events. They may have too
much memory – making it harder to filter out information and increasing
the time it takes for new short-term memories to be processed and
stored.
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The research reinforces the old adage that too much
of anything – even something good for you – can actually be detrimental.
In this case, the good thing is the growth of new neurons, a process
called neurogenesis, in the hippocampus, the region of the brain
responsible for learning and memory.
Results of the study, conducted with mice, found
that the absence of neurogenesis in the hippocampus improves working
memory, a specific form of short-term memory that relates to the ability
to store task-specific information for a limited timeframe, e.g., where
your car is parked in a huge mall lot or remembering a phone number for
few seconds before writing it down. Because working memory is highly
sensitive to interference from information previously stored in memory,
forgetting such information may therefore be necessary for performing
everyday working memory tasks, such as balancing your check book or
decision making.
“We were surprised to find that halting
neurogenesis caused an improvement of working memory, which suggests
that too much memory is not always a good thing, and that forgetting is
important for normal cognition and behavior,” said Gaël Malleret, Ph.D.,
a research scientist at the Center for Neurobiology and Behavior at
Columbia University Medical Center and the paper’s co-first author.
“Altogether, our findings suggest that new neurons in the hippocampus
have different, and in some cases, opposite roles in distinct types of
memory storage, and that excess neurogenesis can be detrimental to some
memory processes.”
“We believe these findings have important
implications for diverse disciplines ranging from medicine to artificial
intelligence,” said Dr. Malleret. “In medicine, these findings have
significant implications for possible therapeutic interventions to
improve memory – a careful balance of neurogenesis would need to be
struck to improve memory without overwhelming it with too much
activity.”
Many scientists had believed that neurogenesis in
the hippocampus, and specifically, the dentate gyrus region, was wholly
beneficial to memory. Previous research by Dr. Malleret with co-first
author Michael D. Saxe, Ph.D., who was at Columbia when the research
took place and is now at the Salk Institute in San Diego, Calif., found
that reducing neurogenesis causes long-term memory deficits.
Based on this research, Drs. Malleret and Saxe
hypothesized that the growth of too many new neurons could actually be
more harmful than helpful to working memory. To examine this hypothesis,
they designed working memory tests for two independent groups of mice in
which neurogenesis in the hippocampus regions was suppressed.
Results of the tests, in which mice had to locate
food within specific areas of a maze, showed that mice in which
neurogenesis had been halted made more correct choices and found the
food faster.
“In our world, we are constantly bombarded by new
information so we are constantly filtering –and if we did not do this,
we would be overwhelmed,” said Dr. Malleret. “Our research indicates
that those with better working memory may have fewer new neurons being
developed in their hippocampus, which helps them forget old and useless
information sooner and enable them to take in new information faster.”
Editor's Notes:
The study is published in the March 23 issue of the
Proceedings of the National Academy of Sciences.
Additional Columbia scientists who were involved in
the research included Nobel laureate Eric R. Kandel, Svetlana Vronskaya,
Indira Mendez, and senior author René Hen. The team also included Denise
Garcia and Michael V. Sofroniew from the University of California, Los
Angeles.
Columbia University Medical Center provides
international leadership in pre-clinical and clinical research, in
medical and health sciences education, and in patient care. The medical
center trains future leaders and includes the dedicated work of many
physicians, scientists, nurses, dentists, and public health
professionals at the College of Physicians & Surgeons, the College of
Dental Medicine, the School of Nursing, the Mailman School of Public
Health, the biomedical departments of the Graduate School of Arts and
Sciences, and allied research centers and institutions.
www.cumc.columbia.edu
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