Word: amygdala
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Dates: during 1990-1999
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...motor skills. An Alzheimer's patient can learn to draw in a mirror but can't remember doing it; a Huntington's patient can't do it but can remember trying to learn. Yet another region of the brain, an almond-size knot of neural tissue known as the amygdala, seems to be crucial in forming and triggering the recall of a special subclass of memories that is tied to strong emotion, especially fear. The hippocampus allows us to remember having been afraid; the amygdala evidently calls up the goosebumps that go along with each such memory...
Anxiety disorders, on the other hand, probably reflect serotonin deficits in the amygdala, the part of the brain that processes fear and other emotions. For depression, bulimia, obesity and the rest of the serotonin-related disorders, however, no one knows for sure what part of the brain is involved or exactly why the drugs work. "There is," says Hyman, "a bit of mystery here...
What the researchers found was striking. Levels of a powerful brain chemical called dopamine dramatically increased in the outermost shell of the nucleus accumbens, a region that is richly endowed with connections to one of the brain's most important emotional centers, an ancient structure known as the amygdala...
...probably no coincidence that the relaxation response and religious experience share headquarters in the brain. Studies show that the relaxation response is controlled by the amygdala, a small, almond-shaped structure in the brain that together with the hippocampus and hypothalamus makes up the limbic system. The limbic system, which is found in all primates, plays a key role in emotions, sexual pleasure, deep-felt memories and, it seems, spirituality. When either the amygdala or the hippocampus is electrically stimulated during surgery, some patients have visions of angels and devils. Patients whose limbic systems are chronically stimulated by drug abuse...
...example, sees a long, curved shape in the grass out of the corner of his eye. He leaps out of the way before he realizes it is only a stick that looks like a snake. Then he calms down; his cortex gets the message a few milliseconds after his amygdala and "regulates" its primitive response...