Word: stressful
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...journey begins when a rat (we'll get to humans later) feels the stress, in this case an electric shock. The rat's senses immediately send a message to the central portion of its brain, where the stimulus activates two neural pathways. One of these pathways is a relatively long, circuitous route through the cortex, where the brain does its most elaborate and accurate processing of information. The other route is a kind of emergency shortcut that quickly reaches an almond-shaped cluster of cells called the amygdala...
...this point, the other half of the stress signal has reached the cortex, which confirms that there's a danger present and figures out that it's causing pain. Once the shock has warn off, a part of the brain called the prefrontal cortex sends out an all-clear message and lets the amygdala know that it's O.K. to stand down. At least it's supposed to. It seems that it's harder to turn off a stress response than to turn it on. This makes sense, in terms of survival. After all, it's better to panic unnecessarily...
...understanding anxiety. Michael Davis, a behavioral neuroscientist at Emory University in Atlanta, has spent six years studying a pea-size knot of neurons located near the amygdala with an impossible name: the bed nucleus of the stria terminalis, or BNST. Rats whose BNST has been injected with stress hormones are much jumpier than those that have got a shot in their amygdala. Could the BNST be at the root of all anxiety disorders? The clues are intriguing, but as scientists are so fond of saying, more research is needed...
...overanxious young children were, on average, much larger than those of their unaffected peers. Perhaps they just had more fear circuits to contend with? Neuroscientists are tempted to say yes, but they admit the conclusion is pretty speculative. Another group of researchers found that patients with post-traumatic stress disorder had a smaller hippocampus than normal. Perhaps their stressful experiences had somehow interfered with the hippocampus' ability to make new memories and, just as important, forget the old ones? Again, no one knows for sure...
...Scott Rauch of Massachusetts General Hospital, is that any area that seems more active than usual while someone is anxious may play an important role in making the person that way. Rauch's team has spent the past eight years scanning groups of combat veterans, some with post-traumatic stress disorder and some without, to see which areas of the brain light up when they hear tapes recounting their most troubling memories. So far, the signals in the amygdala appear to be more active in those with PTSD than in those without. In addition, signals to the prefrontal cortex...