Once dismissive of reconsolidation, LeDoux now researches the phenomenon in rats and is attempting a clinical study that will have people with long-standing PTSD take propranolol immediately after they have an unprompted flashback. But recruiting subjects has been difficult because he needs people who aren’t taking antidepressants or anti-anxiety medications. That rules out a lot of those with PTSD.
LeDoux was discouraged by the results of an earlier experiment in which he gave propranolol to people conditioned to have an adverse reaction to a blue square after receiving a mild shock. Although 24 hours later, those who’d received the beta-blocker reacted less strongly to the sight of the square, their fear ultimately returned. “It’s much easier to study reconsolidation in animals,” says LeDoux. “People can willfully regulate their amygdalas to counteract fear by thinking of other things, so maybe this isn’t a good way to gauge reconsolidation.”
Of course, the problem with reconsolidation experiments could be more fundamental. “Maybe reconsolidation is more complicated than it first seemed,” says LeDoux, and for now, at least, that’s what memory pioneer McGaugh has concluded. Although other laboratories have confirmed the basic findings of reconsolidation, his laboratory and others have been unable to replicate the results of Nader’s experiments, and some who’ve had partial success have found that the fear memory is only temporarily extinguished. “Reconsolidation is a controversial theory right now,” says McGaugh. “It will take at least a few years before we know whether it really happens.”
Pitman, who has spent his career studying PTSD, acknowledges that it’s possible that reconsolidation of traumatic memories doesn’t occur. “That turns out to be the case for many things we try in medicine,” he says. “But based on how patients in the Montreal study have responded to propranolol, we are off to a good start. Sooner or later we may well find a drug that can prevent PTSD or at least reduce the intensity of the memories to a level that a person can more easily live with them.”
 Dossier
1. “Memory Traces Unbound,” by Karim Nader, Trends in Neurosciences, February 2003. Nader lays out the hypothesis that consolidated memories can be modified, strengthened or erased, and eloquently argues that this reconsolidation theory will finally reconcile a 70-year-old dichotomy that memory is both fixed and dynamic.
2. Memory and Emotion: The Making of Lasting Memories, by James L. McGaugh, Columbia University Press, 2003. After having studied memory for half a century, the renowned behavioral neuroscientist explains its mysteries: how memories are made, why some disappear while others are indelible, and the role of stress hormones on our ability to remember and learn.
3. “Pilot Study of Secondary Prevention of Posttraumatic Stress Disorder with Propranolol,” by Roger K. Pitman et al., Biological Psychiatry, Jan. 15, 2002. Preliminary findings that support the hypothesis that propranolol holds promise as a treatment of PTSD.
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