Animal models of PTSD

Both of the papers this week researched post traumatic stress disorder (PTSD) and how it’s seen in the animal model. First, Herry et al’s paper, published in 2008, looked at some of the circuitry involved in both the processes of fear and of extinction. One of the most interesting results of the paper, in my opinion, was that there was no apparent physical connection between the “extinction neurons” and the ventral hippocampus. Even though only a small number of neurons were examined, I still would have thought that some of the ones involved in extinction (which must be related to memory in some capacity) would have some sort of pathway through the hippocampus. This paper has some very good insinuations about the circuitry in other ways as well. Finally understanding these pathways could be vital to understanding not only PTSD, but numerous other anxiety disorders as well.

Next, Reznikov et al’s paper, published in 2015, looked at baseline blood corticosterone levels and baseline anxiety levels as potential predictive measures for weak fear conditioning extinction. It may be due to the varying requirements in structure for both journals, but I thought the Reznikov paper was a lot easier to follow and the figures were a lot more straightforward. I found it improbable that no other papers have been published in which these blood chemistry levels were taken before behavioral testing, but it appears to be the truth and that’s surprising to me.

Some problems that I had with both papers were the techniques used for modeling PTSD in the animals. Both studies used shocks associated with a specific tone as the models for conditioning the animals, however I question the effectiveness of severity of this technique. The tone clearly induces fear and anxiety in the animals after a significant amount of time, yet there is more to the diagnosis of PTSD than just heightened anxiety. These studies only looked at anxiety and could be improved upon significantly by including tests to measure levels of insomnia, anhedonia, or avoidance as well.