Word: amygdala
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What happens biochemically, says McGaugh, is that when faced with an emotion-charged situation, such as a threat, our bodies release the stress hormones adrenaline and cortisol. Among other things, these signal the amygdala, a tiny, neuron-rich structure nestled inside the brain's medial temporal lobes, which responds by releasing another hormone, called norepinephrine. Norepinephrine does two important things. First, it kicks the body's autonomic nervous system into overdrive: the heart beats faster, respiration quickens, and the muscles tense in anticipation of a burst of physical exertion...
...probe the risk-assessment mechanisms of the human mind, Joseph LeDoux, a professor of neuroscience at New York University and the author of The Emotional Brain, studies fear pathways in laboratory animals. He explains that the jumpiest part of the brain--of mouse and man--is the amygdala, a primitive, almond-shaped clump of tissue that sits just above the brainstem. When you spot potential danger--a stick in the grass that may be a snake, a shadow around a corner that could be a mugger--it's the amygdala that reacts the most dramatically, triggering the fight-or-flight...
...danger is real. But that fraction of a second causes us to experience the fear far more vividly than we do the rational response--an advantage that doesn't disappear with time. The brain is wired in such a way that nerve signals travel more readily from the amygdala to the upper regions than from the upper regions back down. Setting off your internal alarm is quite easy, but shutting it down takes some doing...
...fact entirely human. A study by psychologist Alex Todorov shows that we form opinions about a person with a 100-millisecond glance at the face alone. What's more, you can't even blame your higher brain for such bias. The impulse seems to arise in the primitive amygdala. If your prefrontal cortex is your summa cum laude lobe, the amygdala is Barney Rubble. Says Todorov: "This is a case of a high-level judgment being made by a low-level brain structure...
...have brains the size of a normal 13-year-old. This aberrant growth is even more pronounced in girls, he says, although for reasons that remain mysterious, only 1 out of 5 children with autism is female. More recent studies by Amaral and others have found that the amygdala, an area associated with social behavior, is also oversize, a finding Amaral believes is related to the high levels of anxiety seen in as many as 80% of people with autism...