The ability to document the brain as it matures, made possible by harmless, noninvasive imaging techniques, is transforming our understanding of what it means to come of age.
Not so long ago, scientists were convinced that critical periods of brain development occurred only during the first few years of childhood. Long-term imaging surveys, however, reveal that adolescence also is a crucial time in the life of the brain.
By most measures, the teenage years are the healthiest and most resilient time of life; yet they are also among the most volatile and vulnerable. The mental and emotional turbulence of adolescence may reflect dynamic waves of change in parts of the brain associated with impulse control, judgment, attention and anxiety.
Prompted by puberty, impressionable teenage brain cells radically rewire themselves, researchers have learned. At a neural level, consequently, adolescents often process information differently from either children or adults because the anatomy of reason and decision is in such flux. Unused neural circuits are discarded during normal growth and young adults end up with less of the gray matter of neurons than a newborn, even though their brains may become three or four times as big.
The impulsivity and poor judgment of clinical attention-deficit disorders (A.D.D.) in many cases may be caused by a momentary lag in the timing of cortical growth, researchers at the National Institute of Mental Health report in the Proceedings of the National Academy of Sciences. Within a few years, they determined, a normal brain will correct itself.
Even the normal pace of development can exasperate parents and teachers. The scatter-brain qualities of the normal teenager arise, in part, because neural circuits that control our ability to focus mentally on more than one thing at a time don't finish developing until late adolescence, researchers at the University of Minnesota reported recently in the journal Child Development.
Source: Science Journal, The Wall Street Journal, November 23, 2007
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