CAMBRIDGE, Mass.—Aug. 28, 2003—McGovern Institute Reports New Findings In Brain's System
In a paper to be
published today in the journal, Science, Dr. Naotaka Fujii, Research
Scientist at MIT, and Dr. Ann M. Graybiel, Walter A. Rosenblith
Professor of Neuroscience at the McGovern Institute at MIT, report
what may be the brain's system for keeping track of what we do.
We all admire people who keep checklists and check things off.
Drs. Fujii and Graybiel suspect that they may have found the brain's
check mark system and at least one brain site where the brain keeps
its checklist. The checklist is in the prefrontal cortex of the brain,
known for its ability to keep memories ready to use. Drs. Fujii and
Graybiel recorded neural activity in the prefrontal cortex in monkeys
that they had trained to make a simple series of movements. The
neurons they recorded from faithfully responded with each movement,
but they also had an "extra" response when the monkeys finished the
entire sequence of movements.
The experiments described in their report point to the extra
response as being the checkmark - the brain's way to say that the
behavior is done. Having an overactive checklist system could lead to
some of the symptoms people suffer with damage to the frontal cortex.
If the brain thinks actions are done and doesn't have the urge to do
them, apathy can result. Such lack of drive can be a major symptom of
frontal lobe dysfunction. At the other extreme, if the brain lacks its
checkmark system, behavior may get repeated over and over again.
Perseverative behaviors are a classic symptom of frontal lobe damage.
It is as though the "it's done" signal is missing. Repetitive
behaviors and thoughts are also features of obsessive compulsive
disorder (OCD) and a range of related disorders that affect both
children and adults.
This work also suggests that the prefrontal cortex-basal ganglia
brain regions that the researchers recorded from help "package" the
individual parts of sequential behaviors into larger chunks. The same
nerve cells that make the checkmark also accentuate their activity at
the beginning of a movement sequence. A defect in this chunking system
may underlie some of the symptoms of Parkinson's Disease, in which the
patient has to think out each part of a sequence, even a "simple"
movement sequence like standing up from a chair.
Dr. Fujii is an ophthalmologist from Japan who has specialized in
recording the activity of brain cells while primates carry out eye
movement tasks. He was promoted to the rank of Research Scientist at
MIT in 2001. Dr. Graybiel's groundbreaking research focuses on normal
and abnormal behaviors associated with the basal ganglia, and their
relationships to dopamine regulation. Dr. Graybiel studies the
neurophysiology of the basal ganglia, a brain region that is
implicated in the control of movement and cognition, as well as in our
ability to learn habits. Disorders in this region have been implicated
in Parkinson's and Huntington's diseases, and in neuropsychiatric
disorders such as Tourette's syndrome, obsessive-compulsive disorder,
depression, and also addiction.
Dr. Graybiel joined the MIT faculty in 1973 and in 1994 was named
Walter A. Rosenblith Professor of Neuroscience in the Department of
Brain and Cognitive Sciences. In 2001, she was appointed Investigator
at the McGovern Institute. She received her Ph.D. in 1971 from MIT.
Graybiel is a member of the National Academy of Sciences, the
Institute of Medicine, and the American Academy of Arts and Sciences.
Graybiel was named a recipient of the 2001 National Medal of Science,
the nation's highest science and technology honor.
About the McGovern Institute at MIT
The McGovern Institute for Brain Research at MIT is a research and teaching institute
committed to advancing human understanding and communications. The goal of the McGovern
Institute is to investigate and ultimately understand the biological basis of all higher brain function
in humans. The McGovern Institute conducts integrated research in neuroscience, genetic and
cellular neurobiology, cognitive science, computation, and related areas.
By determining how the brain works, from the level of gene expression in
individual neurons to the interrelationships between complex neural
networks, the McGovern Institute's efforts work to improve human health,
discover the basis of learning and recognition, and enhance education and
communication. The McGovern Institute contributes to the most basic
knowledge of the fundamental mysteries of human awareness, decisions, and
actions.
For additional information, please go to http://web.mit.edu/mcgovern.
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Lyn Chamberlin
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