MYSTERIES OF THE MIND

Researcher looks to extinguish fear triggered by memories of traumatic events



But recollecting is not forgetting,

It's vivid rehearsal of pain.

It reminds me of that day.

It keeps fear in my brain.

Those lyrics are from the song "Fearing," and the man who wrote them, neuroscientist Joseph LeDoux, is leading the way on research that may permanently extinguish some of the fears that are triggered by the memory of traumatic events.

Mr. LeDoux is a researcher based at New York University, and he has spent much of his career investigating the function of the amygdala, the "fear center" in our brains. He may also be one of the few brain researchers with his own rock group. He and his fellow scientist-musicians call themselves the Amygdaloids, and their songs often describe the mechanisms of the mind.

The song "Fearing" is based in part on the poetry of Emily Dickinson, who once wrote of fear that " 'Tis harder knowing it is due, than knowing it is here."

Her words evoke the familiar Pavlovian story of how we associate certain signals with pain or trauma, so that the sight or sound of them -- or the memory of them -- dries our mouths, sets our hearts racing and makes our hands sweaty. The same process has also been linked to the cravings addicts experience, whether it's the sight of a bar sparking desire for a drink or the click of a roulette wheel triggering the urge to gamble.

The standard treatment for phobias -- unusually intense fears that people have to certain objects or situations -- is called exposure therapy, where the person encounters the thing that he fears, and if nothing bad happens after several exposures, the fear subsides.

The problem with that, Mr. LeDoux explained at an interview in his office, is that the deep-rooted fear never really goes away, and a future trauma or intense stress can cause the phobia to reappear.

Now, however, there is a therapy that holds out the hope of eliminating the fear altogether.

It relies on recent findings that when animals or people recall something, there is a short period of time, perhaps 10 minutes to four hours, when that memory is "labile," meaning it can be reshaped before it solidifies again in the brain.

He and other scientists have used that insight to tweak a classic exposure procedure in such a way that mice "forget" to respond to a signal that once petrified them.

Rats can be taught to associate a certain auditory tone with an electric shock to their feet. They will then freeze as soon as they hear the sound.

Exposure training eliminates that response by playing the tone several times with no resulting shock. However, if the shock is introduced again later after they hear the tone, they will start freezing again every time they hear the tone.

Scientists have now shown that if they get the animals to recall the fear by playing a tone, and then wait about 10 minutes before starting the repeated tones with no shocks, they can eliminate the fear response permanently.

And in new work, other groups are showing the same technique works in humans.

Two of Mr. LeDoux's colleagues, Daniela Schiller of Mt. Sinai Hospital and Elizabeth Phelps of NYU, recently published work showing that in students who volunteered to get a shock on the wrist after seeing certain colored squares, the technique of showing them one of the colored squares two days later -- so they remembered the experience -- and then waiting 10 minutes before showing them more of the colored squares with no following shocks, seemed to eliminate their fear completely, as measured by a lack of sweating on the skin.

In a more real-world setting, scientists in China used the same technique with heroin addicts who were in recovery. They showed them videos of heroin use to trigger memories of their past drug abuse, then waited about 10 minutes to show them repeated images of drug use or give them drug paraphernalia to touch.

The addicts who got that exposure therapy after 10 minutes showed reduced cravings for heroin up to half a year later. But addicts who were given the exposure therapy six hours after the memory retrieval didn't show less desire for drugs, suggesting the shorter window of time after a memory is recalled is critical for permanently changing its association with drug cravings.

The theory for why this works, Mr. LeDoux said, is that classical exposure training is teaching the brain's prefrontal cortex to put a lid on the responses seated deeper in the brain, but that the new carefully timed exposure method is directly lessening the intensity of the response from those deep-brain areas.

If further work shows that stubborn fears or cravings can be permanently erased, it would offer hope to thousands who suffer from various phobias, addictions or post-traumatic stress disorder.

And it's already generated a couple of new songs for the Amygdaloids.


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