Week 4 PTSD: Herry et al. (2008) and Reznikov et al. (2015)

Both the Herry et al. (2008) and Reznikov et al. (2015) studies yielded intriguing results. While the Herry et al. research focused on identifying the neurons and circuits involved in fear and extinction responses to fear conditioning, that of Reznikov et al. proposed a new model for examining PTSD.

With regards to the Herry et al. (2008) study, I found their data highly convincing. Their results for fear conditioning, as well as the subsequent data from the electrode recording of neuronal firing in response to the conditioned stimuli, provide very clear evidence for the distinct existence and roles of fear neurons and extinction neurons within the BA. The inclusion of the data relating to the order of the neuronal activity in relation to behavior is also incredibly significant given that it indicates that the extinction neurons increase in firing as the fear neurons decrease in firing and then the behavior change of diminished freezing occurs. Additionally, I found their conclusions relating to fear memory enlightening, specifically the importance of memory reconsolidation for fear prevention in the fear context. Given the contextual nature of fear and extinction, I am curious as to the future therapeutic applications for human PTSD. It seems that somehow simulating the traumatic event may be helpful to reactivate the fear memory in an attempt to eradicate it, but causing feared trauma to erase feared trauma memory could be potentially harmful given the complexity of traumatic events. For instance, if a soldier is diagnosed from PTSD from war, what aspect or experience from the war exactly should be targeted in trying to eliminate the fear and how could that element be reproduced safely?

In contrast, the Reznikov et al. (2015) data provided equally interesting but slightly less convincing results. Nevertheless, I respect their utilization of identifying those who develop PTSD as a minority subpopulation, and also appreciate the longevity of their study, all of which were not accounted for in previously established PTSD models. I was especially surprised by the results from the corticosterone levels examined prior to fear conditioning given that I assumed the weak extinction group would have higher corticosterone, not lower. While I am a proponent of their PTSD model, I do think they need a larger population, as well as more clearly defined groups for their correlations before it can be considered for therapeutic applications.