Part I: Memory Formation and Drug Research on PTSD
An article entitled Erasing Painful Memories in the May 2012 issue of Scientific American reviews some of the current research on the treatment of post-traumatic stress disorder (PTSD).
Memory is no longer seen as a passive process of recording impressions. Rather, it is ongoing activity at the cellular and neurochemical level. It is this ongoing activity that allows some new openings for medical intervention.
We tend to think of a memory as a kind of object or a file that can be recalled when needed. But that’s not the case. We are finding out that memory is stored in at different sites in the brain. For example, the auditory part of a particular memory is stored in the auditory cortex in the temporal lobe, and the visual part of the same memory is stored in the visual cortex. When that memory occurs, those various memories are “reassembled” into a single, unified experience. That’s why we now think that memory is not so much “recalled” as it is “recreated”. If so, it is might be possible to “un-create” memories too. That could be hugely helpful in treating PTSD.
The basic animal used in research of memory is the lab rat. When a caged rat is given a single mild shock to its foot, the rat turns around and heads in the opposite direction. It never returns to the spot where it received the shock. A rat will play out this avoidance over and over. Without an intervention, the rat will never learn that the shock will not be repeated. In other words, the rat is stuck with the original traumatic memory.
In 2006 a scientist injected a compound directly into the memory center of a rat’s brain that had been exposed to a foot shock. The compound interfered with new memory formation. Afterward the rat exhibited no fear behavior—the fear was no longer there. The original fear memory had been blocked from “re-creating” itself. The only problem with this approach is that it’s not specific for traumatic memories; it affects non-traumatic memories as well. It’s too non-specific to be practical.
Another neurochemical approach involves not removing particular memories but in removing the “charge” associated with a traumatic memory. The emotional “charge” provokes physical symptoms of fear such as increased heart rate and faster breathing.
A drug that reduces the body’s fear reaction is propanolol. It slows down the pulse and heart rate, thereby limiting the “fight or flight” response. While it was hoped that injecting propanolol within a few hours of exposure to trauma might prevent PTSD from becoming established, current studies have been mixed.
› Part II of this blog will cover some of the newer non-drug approaches to treating PTSD.