Closing the Window of Fear

Excessive fear is the cause of many psychopathologies. Although pharmacological interventions can help in preventing the retrieval of fear memories, they are toxic and involve a lot of side-effects. Till now, non-pharmacological interventions were only effective in suppressing the memory of fear for a short period. A new technique developed by scientists at the Center for Neural Science and New York University has generated a lot of interest in the in the field of psychological therapy.

According to a hypothesis called the reconsolidation theory, fear memories are consolidated every time they are recalled. Following an episode of fear stimuli, it’s memory becomes unstable for some time which allows it to be updated. This window period of reconsolidation has provided scientists with a tool to modify it.

Fear extinction is a well established procedure that involves unlearning of fear associated with a stimuli by repeating it in a safe or non-hazardous manner, so that the fear is dissociated with the stimuli. However, this method does not alleviate the phobia permanently as in most cases the fear comes back. Scientists have now discovered that if this extinction training is given in the window period before reconsolidation of fear memory occurs it can be more effective. For humans, this window period was identified as a period of 6 h within the reminder of the fear stimuli.

In a human experiment, 65 volunteers were shown two differently colored squares, one of which was combined with a shock to the wrist.  The volunteers were divided into three groups, based on whether they were re-exposed 6 h or 10 min before the extinction procedure or not re-exposed to the fear stimuli at all. In the group where this extinction procedure was performed without re-exposure or 6 h after the re-exposure to the stimuli, spontaneous recovery of the fear response occurred on the first re-exposure trial. However, the volunteers who were re-exposed to the stimuli 10 min before extinction procedure showed no fear response to it even a year later.

These effects were highly specific to the stimuli. When two different squares paired with a shock were used, the subjects showed a reduced fear response only to the square of which they had been reminded before the extinction procedure. Interfering with the reconsolidation of one stimulus did not affect the memory of another, similar stimulus. Moreover, this therapy does not tamper with the memory in any way. In the experiment, all subjects distinctly remembered the color of the square paired with the shock stimuli, and only the fear response associated with it was gone.

Thus, introduction of a reminder of fear stimuli before extinction therapy results in a long-lasting blockade of the fear memory compared to extinction therapy alone. The importance of this work lies in its non-invasive technique and its non-dependence on drugs in rewriting the fear memories. Since fear extinction is a critical component of nearly all cognitive and behavior therapies, this study is expected to directly translate into improved treatment procedures for post-traumatic stress disorder and other anxiety conditions. Clinical application of this more naturalistic intervention to erase fear memories should be a significant step in psychotherapy.

References

Schiller, D., Monfils, M., Raio, C., Johnson, D., LeDoux, J., & Phelps, E. (2009). Preventing the return of fear in humans using reconsolidation update mechanisms Nature, 463 (7277), 49-53 DOI: 10.1038/nature08637

Schiller, D., Monfils, M., Raio, C., Johnson, D., LeDoux, J., & Phelps, E. (2009). Preventing the return of fear in humans using reconsolidation update mechanisms Nature, 463 (7277), 49-53 DOI: 10.1038/nature08637