Imaging Study Shows Brain Maturing
The brain's center of reasoning and problem solving is among the
last to mature, a new study graphically reveals. The decade-long
magnetic resonance imaging (MRI) study of normal brain development,
from ages 4 to 21, by researchers at NIH's National Institute of
Mental Health (NIMH) and University of California Los Angeles (UCLA)
shows that such "higher-order" brain centers, such as
the prefrontal cortex, don't fully develop until young adulthood.
A time-lapse 3-D movie that compresses 15 years of human brain
maturation, ages 5 to 20, into seconds shows gray matter
the working tissue of the brain's cortex diminishing in a
back-to-front wave, likely reflecting the pruning of unused neuronal
connections during the teen years. Cortex areas can be seen maturing
at ages in which relevant cognitive and functional developmental
milestones occur. The sequence of maturation also roughly parallels
the evolution of the mammalian brain, suggest Drs. Nitin Gogtay,
Judith Rapoport, NIMH, and Paul Thompson, Arthur Toga, UCLA, and
colleagues, whose study is published online during the week of May
17, 2004 in The Proceedings of the National Academy of Sciences.
"To interpret brain changes we were seeing in neurodevelopmental
disorders like schizophrenia (http://www.nimh.nih.gov/healthinformation/schizophreniamenu.cfm),
we needed a better picture of how the brain normally develops,"
The researchers scanned the same 13 healthy children and teens
every two years as they grew up, for 10 years. After co-registering
the scans with each other, using an intricate set brain anatomical
landmarks, they visualized the ebb and flow of gray matter - neurons
and their branch-like extensions in maps that, together, form
the movie showing brain maturation from ages 5 to 20.
It was long believed that a spurt of overproduction of gray matter
during the first 18 months of life was followed by a steady decline
as unused circuitry is discarded. Then, in the late l990s, NIMH's
Dr. Jay Giedd, a co-author of the current study, and colleagues,
discovered a second wave of overproduction of gray matter (http://www.nimh.nih.gov/publicat/teenbrain.cfm)
just prior to puberty, followed by a second bout of "use-it-or-lose-it"
pruning during the teen years.
The new study found that the first areas to mature (e.g., extreme
front and back of the brain) are those with the most basic functions,
such as processing the senses and movement. Areas involved in spatial
orientation and language (parietal lobes) follow. Areas with more
advanced functions integrating information from the senses, reasoning
and other "executive" functions (prefrontal cortex)
In a related study published a few years ago, Rapoport and colleagues
discovered an exaggerated wave of gray matter loss (http://www.nimh.nih.gov/press/nimhprschizteens01.pdf)
in teens with early onset schizophrenia (http://www.nimh.nih.gov/publicat/schizkids.cfm).
These teens, who became psychotic prior to puberty, lost four times
the normal amount of gray matter in their frontal lobes, suggesting
that childhood onset schizophrenia "may be an exaggeration
of a normal maturation process, perhaps related to excessive synaptic
pruning," note the researchers. By contrast, children with
autism show an abnormal back-to-front wave of gray matter increases,
rather than decreases, suggesting "a specific faulty step in
Also participating in the new study were: Leslie Lusk, Cathy Vaituzis,
Tom Nugent, David Herman, Drs. Deanna Greenstein, Liv Clasen, NIMH;
Kiralee Hayashi, UCLA.
The graphic "Time-Lapse Imaging Tracks Brain Maturation from
ages 5 to 20" is available at http://www.nimh.nih.gov/press/prbrainmaturing.cfm.
A Time-lapse Imaging movie is available at http://www.nimh.nih.gov/press/prbrainmaturing.mpeg.
NIMH is part of the National Institutes of Health (NIH), the
Federal Government's primary agency for biomedical and behavioral
research. NIH is a component of the U.S. Department of Health and