Can Fear Be Forgotten?
If fear really is all in our heads, Joseph LeDoux thinks he can eliminate it. The first step is to block out our memories.

After a two-decade-long pursuit into the depths of the brain neuroscientist Joseph LeDoux has shown that it's possible to eliminate deep-seated fears. All you have to do is remove the memory that created it.
Last year, in a landmark experiment in rats, LeDoux opened a path to doing just that. He showed that it's possible to obstruct the memory of a specific traumatic event without affecting other memories. He also demonstrated that when the memory was stifled, the fear it roused vanished as well.
This sudden ability to produce selective amnesia stunned the scientific community. It also offers unimaginable promise. It could relieve soldiers suffering from post-traumatic stress disorder (PTSD) or rid sexual abuse and rape victims of haunting memories.
Other researchers have been quick to adapt LeDoux's findings. One has already begun experimenting on human subjects, and a startup company has emerged that plans to eliminate fears in the comfort of your own home. All you need is a mail-order box of pills and the accompanying DVD.
To understand why rats—and other animals, including humans—get scared, you have to start at the amygdala, the place where sensation and memory join forces to spawn the venerable beast we call fear. The amygdala is buried in the forebrain directly behind the eyes. LeDoux first started researching the amygdala in the late 1970s with early experiments that investigated how rats adapt to danger.
The study revealed that when it comes to fear, the "thinking" part of your brain is instinctively subordinate to the amygdala. Your fears forestall your thoughts, and the amygdala is the reason why. It takes a new input, checks it against your fear memories and, if there's a match, initiates a response.
Without the fear memory, though, the chain falls apart: If my brain can't remember why I'm afraid of spiders, then I won't be afraid of spiders. Yet selectively eliminating a memory would seem to be impossible. LeDoux suspected it was not.
What Fear Does to the Brain Say you're afraid of mice. When the eye sees one skitter, it transmits the data to the thalamus [A], which sends the information straight to the the amygdala [B] and the visual cortex [C]. The amygdala rapidly associates the image with a fear memory and tells the hypothalamus [D] to prime the body for action. Meanwhile, the visual cortex goes through the higher-level processing of the image, but rationalization (it's just a mouse!) is too late [E] to overcome the amygdala's immediate repsponse.
It's certainly possible that eventually we'll have enough skills to manipulate our own fears, memories and emotions. But according to Ledoux, we won't reach that point until "we stop thinking of the brain as a bunch of systems and start thinking of it as a system itself." This conviction betrays a hope for the future of his field—that someday, instead of treating the brain as a collection of dissimilar mechanisms, scientists will approach it (and understand it) holistically.
"As individuals we are not the mere sum of our perceptions, fear memories, thoughts and emotions, but synergistically something more," says Ledoux. "This is the big problem brain research needs to solve—how our brains make us who we are."
Kemo D. (a.k.a. no.7)  
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