In the brain, these thoughts can often be traced to overreactivity in the amygdala, a small site in the middle of the brain that, among its many other functions, responds to novelty and threat. When the amygdala works as it should, it orchestrates a physiological response to changes in the environment. That response includes heightened memory for emotional experiences and the familiar chest pounding of fight or flight. But in people born with a particular brain circuitry, the kind seen in Kagan’s high-reactive study subjects, the amygdala is hyperreactive, prickly as a haywire motion-detector light that turns on when nothing’s moving but the rain. Other physiological changes exist in children with this temperament, many of them also related to hyperreactivity in the amygdala. They have a tendency to more activity in the right hemisphere, the half of the brain associated with negative mood and anxiety; greater increases in heart rate and pupil dilation in response to stress; and on occasion higher levels of the stress hormones cortisol and norepinephrine.
MrGhaz . on 21 Nov 09Millions of people watch a rock concert relayed to opposite ends of the world. A fire fighter wearing breathing apparatus spends 25 minutes in a burning building rescuing a trapped child. A prospective buyer watches as a mechanic runs a complete check on a used car. On a remote Texas ranch, water is heated with solar panels. An orthopedic surgeon analyzes the muscle movements of a victim of cerebral palsy. A student in a college dormitory spots an intruder and triggers a portable alarm. These seemingly disconnected events have all been made possible by an advanced technology that has made a radical difference in day-to-day life on earth: they are all spin-offs from NASA's space exploration programs.
