Ending the fear
In a recent study led by Vici award recipient Merel Kindt (Full Professor of Experimental Clinical Psychology, University of Amsterdam), a team of researchers succeeded in reducing fear responses among human test subjects.
In a recent study led by Vici award recipient Merel Kindt (Full Professor of Experimental Clinical Psychology, University of Amsterdam), a team of researchers succeeded in reducing fear responses among human test subjects. Specifically, when administered the beta blocker propranolol in combination with memory retrieval, subjects were less troubled by fearful memories. Even more remarkable is that fear responses did not return after a well-established retrieval technique for fear responses. The researchers' findings were published in the 15 February issue of the leading journal Nature Neuroscience.Until recently it was commonly assumed that fear memories are impossible to eradicate. However, this study proves that intervening in human emotional memory is in fact possible.
Saving changes
Recently, it was rediscovered that fear memory in animals is not necessarily permanent, but can change when retrieved. The reactivation of a consolidated (fear) memory can return it to a labile, supposedly protein synthesis-dependent state, a process referred to as reconsolidation. Reconsolidation of fear memory can be influenced by neurobiological manipulations during or shortly after the reactivation period. The manipulations are thought to alter protein synthesis directly or by interacting with the release of neurotransmitters (e.g. norepinephrine) within the amygdala. At the behavioral level, this may lead to changes in later expressions of that fear memory.As part of the study, test subjects were shown pictures of two different spiders. One of the pictures was always folowed by a pain stimulus, while the other was not. After time the participants automatically displayed a frightened response (fear) when shown the fear conditioned spider, even when the pain stimulus was not administered. The subjects' fear of the spider was therefore a conditioned response.
Test subjects then returned the next day, when researchers reactivated their fear memories and generated a new protein synthesis. Before reactivating the memory (90 minutes), however, one group of test subjects were administered the beta blocker propranolol. When subsequently shown the picture of the spider the next day, the propranolol group displayed no fear response, unlike the control group (administered a placebo), which did display fear. Among the subjects who had received propranolol, but whose memory was not reactivated, the fear response continued to be strong. The actual fear response was measured by placing two electrodes under subjects' eyes to record blink reflexes. This technique makes it possible to measure responses initiated directly by the amygdala, the brain's emotional centre.
Search in deleted items
At present, cognitive behavioural therapy is the dominant and most effective method used to treat phobias. The treatment involves exposing patients to the object of fear without the feared consequence. Yet, in many cases, the results are short-lived, and the fear returns with the passage of time.One notable finding to come out of this study is that even after subjects had been treated with propranolol and their memories were reactivated, the fear memories could not be recalled through the well-established retrieval technique for fear responses technique of administering (reinstatement: unreinforced pain stimuli). This indicates that the fear memory was either fully eradicated, or is no longer accessible. Thus, while the test subjects could still remember the connection between the spider and the pain stimulus, this memory no longer generated an emotional response. Kindt and her team will use follow-up studies to continue investigating the effects of propranolol in humans over the longer term.
Treating phobias
According to the researchers, the study's results can contribute to developing new procedures for treating those suffering from phobias. Compared with conventional methods, the memory intervention tested here represents an entirely new approach. Traditional cognitive behavioural therapies tend to target the creation of new memories, whereas this method focuses on weakening the fear memories itself.Merel Kindt received a Vici grant from the Netherlands Organisation for Scientific Research (NWO) in 2007 to carry out her innovative study. The research team consisted of Kindt, Marieke Soeter and Bram Vervliet and was conducted at the University of Amsterdam.