How Our Brains Make Memories

Surprising new research about the act of remembering may help people with post-traumatic stress disorder

Memories are stored in a region of the brain called the hippocampus, shown in red in this computer illustration. (Photo Researchers, Inc.)
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Even now, Brunet says, the drugs and psychotherapy conventionally used to treat PTSD do not provide lasting relief for many patients. “There’s still plenty of room for the discovery of better treatments,” he says.

In Brunet’s first study, PTSD patients took a drug intended to interfere with the reconsolidation of fearful memories. The drug, propranolol, has long been used to treat high blood pressure, and some performers take it to combat stage fright. The drug inhibits a neurotransmitter called norepinephrine. One possible side effect of the drug is memory loss. (In a study similar to Nader’s original experiment with rats, researchers in LeDoux’s lab have found that the drug can weaken fearful memories of a high-pitched tone.)

The patients in Brunet’s study, published in 2008, had each experienced a traumatic event, such as a car accident, assault or sexual abuse, about a decade earlier. They began a therapy session sitting alone in a nondescript room with a well-worn armchair and a television. Nine patients took a propranolol pill and read or watched TV for an hour as the drug took effect. Ten were given a placebo pill.

Brunet came into the room and made small talk before telling the patient he had a request: he wanted the patient to read a script, based on earlier interviews with the person, describing his or her traumatic experience. The patients, all volunteers, knew that the reading would be part of the experiment. “Some are fine, some start to cry, some need to take a break,” Brunet says.

A week later, the PTSD patients listened to the script, this time without taking the drug or a placebo. Compared with the patients who had taken a placebo, those who had taken the propranolol a week earlier were now calmer; they had a smaller uptick in their heart rate and they perspired less.

Brunet has just completed a larger study with nearly 70 PTSD patients. Those who took propranolol once a week for six weeks while reading the script of their traumatic event showed an average 50 percent reduction in standard PTSD symptoms. They had fewer nightmares and flashbacks in their daily lives long after the effects of the drug had worn off. The treatment didn’t erase the patients’ memory of what had happened to them; rather, it seems to have changed the quality of that memory. “Week after week the emotional tone of the memory seems weaker,” Brunet says. “They start to care less about that memory.”

Nader says the traumatic memories of PTSD patients may be stored in the brain in much the same way that a memory of a shock-predicting tone is stored in a rat’s brain. In both cases, recalling the memory opens it to manipulation. Nader says he’s encouraged by the work so far with PTSD patients. “If it’s got any chance of helping people, we have to give it a shot,” he says.

Among the many questions that Nader is now pursuing is whether all memories become vulnerable when recalled, or only certain memories under certain circumstances.


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