Reznikov et al

Out of everything we have read so far, I think that Reznikov et al have impressed me the most with their animal model. As we have discussed at length, human mental illness is complex, and creating a model that accurately depicts a disorder is a huge challenge. As we know, PTSD affects only a certain portion of the population; even if two people are exposed to exactly the same trauma, one may develop PTSD while the other does not. Knowing this, it seems foolish to try to develop effective treatments or determine risk factors for PTSD simply by traumatizing a group of rats. Almost by definition, some of the rats you would end up studying don’t have PTSD.  By studying how well animals could extinguish a conditioned fear, I think Reznikov et al identified a very important tool that could be used in future research. By studying only the rats that are outliers, and have atypical trouble un-learning a fear, we will probably make much more progress in helping humans with the same problem.

            I thought that their identification of a cortisol threshold was also very interesting (Figure 5B). This shows that all rats that were “weak extinguishers” had low cortisol, but some “strong extinguishers” had low cortisol as well. This suggests that while having low cortisol levels makes an animal more likely to develop PTSD-like symptoms, there are still many animals that will behave normally even with low cortisol. I think this points to the need to look for differences between low cortisol rats that do and do not develop systems, as it could shed light on additional information. I did think that their categorization of the weak/strong extinguishers based on the top or bottom 30% scoring animals was a bit arbitrary. It was unclear to me why 30% was the best cutoff number, and I would have liked to see some data from the “intermediate” rats. For example, I think that seeing a full chart of all the cortisol levels across the population would have been very interesting.