Can Fear Be Forgotten?

The Core Question

Trials like Tikvah's are designed to answer the most basic questions about using DCS as a fear pill, including dosage and whether it corrupts other memories or cognitive functions. LeDoux suspects that as these move forward, however, researchers will run into some serious troubles. "Complex memories are spread across hundreds of thousands of neurons" through different regions of the brain, LeDoux explains. "The same neurons can participate in many memories." Just because you can tamper with a fear memory in the amygdala doesn't mean you're not mistakenly destroying or adversely altering a memory (or an entire collection of related memories) somewhere else in the brain.

This point is critical. Fear is fused to basic instincts embedded in systems throughout the brain-instincts that evolved over millions of years to protect life and limb. You don't want to erase a person's fear of heights only to find out later that he jumped off a bridge believing he could fly. I need to retain the knowledge that some spiders are deadly poisonous even when my fear of them has been eliminated.

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."

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Michael Behar's last story for Popular Science, "The Prophet of Garbage," appeared in March 2007.