Easing the pain of difficult memories sounds like a dream come true, perhaps even for people who don’t suffer from anxiety disorders. But the idea also raises concerns. Such memories, after all, are an integral part of a person: frightening, sad, perhaps life-changing moments make up important chapters in the stories of our lives. We might not be the same if remembering these events felt no more emotional than recalling a trip to the grocery store.
But Brunet points out that he is trying to bring PTSD patients’ memories into a normal emotional range, not blunt their power altogether. “Months after a breakup, when the pain is beginning to fade away, do you feel that you have lost something?” he asks. “Of course not. That’s the fate of normal emotional memory.” In PTSD, on the other hand, the memory is as painful and crippling as if the events had occurred yesterday, making it difficult to lead a normal life. He doesn’t think that using propranolol to render these memories bearable would create any unique potential for abuse as a way to dull the regrets, fears, and embarrassments of everyday life; people already use alcohol and other drugs for such purposes.
The ethical worries may stem in part from a misunderstanding about the level of control that scientists have over memory. Researchers can manipulate memories only in very subtle ways. It’s not possible to erase a web of interconnected memories, or to program people with substantial new memories. (Research into false memories and eyewitness testimony suggests that a memory can be subtly influenced: someone who has witnessed a car accident, for example, may estimate different speeds for the car depending on whether they are asked how fast they saw it “smash” or “bump” into a tree. But these changes are minor tweaks to existing memories.)
It’s still too early to predict the ultimate impact that drugs and other treatments targeting reconsolidation will have on human memory. But for now, the power to block reconsolidation is giving scientists a new tool to probe the brain’s storage system. Nader’s next step is to use his research on reconsolidation to study how the brain files memories. If rats are taught two different associations–say, pairing a light with a shock and a sound with a shock–does blocking the reconsolidation of one memory affect the other? Experiments like this will begin to shed light on whether memories are stored according to when they were formed, the context in which they were formed, or other variables. Bit by bit, the answers to such questions should help unravel one of the most enticing mysteries of the mind.
Emily Singer is Technology Review’s senior editor for biomedicine.