When Fear Floods Back

Since the time of Pavlov and his dogs, scientists have known that frightening memories we thought we had put behind us can sometimes pop up at inconvenient times. UT neuroscientists recently found that a very specific group of cells in the brain are to blame. Michael Drew, a University of Texas at Austin associate professor, identified the neurons that, when activated, suppress scary memories and when inactivated cause those negative memories to resurface. His finding explains both how this process works in the brain and where (not in the amygdala, which dictates other fear memories, but in the hippocampus, the part of the brain involved with other types of recall).

The discovery may prove helpful for health professionals working to make more effective decisions about treating anxiety, phobias and post-traumatic stress disorder. For example, exposure therapy is one of the leading ways to treat these disorders — but it sometimes stops working. To override past fears, the therapy promotes formation of new memories of safety; for example, a person who had a frightening incident with spiders might practice letting a harmless spider crawl on him. But since the same part of the brain is involved, whether creating the new safe memories or bringing up the older, fear-inducing ones, some competition for resources may come into play.

“The new memory does not erase the original fear memory but instead creates a new memory that inhibits or competes with the original fear,” Drew said. 

Given the new discovery, mental health professionals may need to rethink the duration and timing of exposure therapy, and pharmaceutical makers now have a new pathway for exploring ways to treat fear-based conditions.