Tuesday, December 21, 2010

Spiders 2: The Physiology of Fear

Anxious? Then, most likely, the amygdala is to blame. People with damaged amygdalas (like SM mentioned yesterday) have abnormal emotional responses. SM doesn’t feel fear, and scans of her brain show an amygdala full of lesions. Scientists (H. Kluver and P.C. Bucy in the thirties and N.H. Kalin in 2001) damaged the amygdalas in monkeys (poor things) and noted that they became completely tame—they lost their fear responses.

The amygdala is the part of the brain that remembers when something bad happens and tells us how to react. Anxiety, fear, and aggression are all controlled by it, meaning a malfunctioning one can create anxiety disorders, depression, phobias, and even autism and schizophrenia. That isn’t to say it’s all physiological; post-traumatic stress disorder is also related the amygdala, but it is an acquired condition, not a preexisting one. And since cognitive behavioral therapy also helps with the above disorders, a “broken” amygdala can sometimes be “fixed.”

Psycheducation.org has some nice pictures of the amygdala’s location. If you go back to the fear article about SM, you can see that the pictures of her brain are missing an amygdala. Growing up with no fear (or anger, if Wisegeek is correct), she can’t discern the emotion on anyone or associate danger with situations. She might remember being attacked, but she has no instinctual response, i.e. if someone grabs her, she won’t reflexively fight back. There is no “fight or flight” with her. Just “huh; this is happening.”

While not knowing fear or anxiety might sound like a good thing, in reality, it’s pretty dangerous. SM walks down a dark street and fear doesn’t make her tighten her hand on her purse or listen for following footsteps. If a bomb goes off, she won’t duck unless she actually thinks “Oh, I should duck before a piece of shrapnel hits me.” And the amount of time it takes her to think that might take one second longer than she has before a shard of metal embeds itself in her skull.

Tune in tomorrow for concluding thoughts and credits. I know. I'm really drawing this out, aren't I? I'll post some cute cat pictures on Thursday. Hey. It'll be my hundredth post. I can do what I want. Peace!


  1. Really interesting. Thanks for sharing this. I <3 science. :)

  2. That is absolutely fascinating. I had never heard of that before.

  3. I suppose this is a mixed blessing - a bit like not being able to feel pain. Fear and pain are there for a reason and we could end up damaged without them.

    I'm interested in the idea that some of the people described as 'brave' or 'heroic' may also have this condition and yet for someone with an over-active amygdala it might be the bravest thing in the world for them to get out of bed in the morning.


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