Sial et al examines the paradigm of emotional stress (ES) by have mice observe another mouse undergo physical stress (PS) through the abuse of an aggressor in the vicarious social defeat stress (VSDS) model. While Sial’s research is intuitive on larger scale, big picture objective with many examples of PTSD evolving from witnessing a traumatic even in humans, I am not sure if mice have as complex networks as humans that make this as clear cut. In humans, PTSD from witnessing a traumatic event is common as the complexity of human emotion and subsequent networks, but in mice defining “emotion” is more complicated because we cannot ask a mouse how it is feeling. Nonetheless, Sial’s study captured that witnessing a traumatic event can induce a depressive like phenotype similar to the mouse undergoing the PS. Conceptually, I wonder how much of the induced phenotype is from emotional stress so much as fear of being attacked itself. To capture a glimpse into a more empathetic response, I think it would have been interesting to explore how mice with social bonds reacted to one another being hurt, if it would have increased the loss of weight and corticosterone levels. Additionally, I wish that the study had utilized more measures of depression and stress than weight change, corticosterone levels, elevated plus maze, and social interaction test. It would have been interesting to visualize the brains of these mice as well to see if there were any observable differences in activation patterns of control, ES, and PS mice. Lastly, I would have liked to see potential measures of recovery time and how emotional and physical stress mice differed in this.
Allsop et al answered many of the questions that Sial’s paper spurred, specifically they included the neural response observed in the observational fear paradigm. The researchers examined many many aspects of the observational fear learning that were able to capture an interesting story of the observational fear learning pathway. Again, the paper solidified that observational, or the correlate of emotional in Sial’s paper, fear learning can have just as detrimental effects as physical stress. They took it a step further and examined neuronal activation and observed that the ACC à BLA pathway was necessary for observational fear conditioning but not classical fear conditioning. This detail specifically stood out to me; it makes sense that the BLA would be involved in fear conditioning and emotion, but the ACC must play a crucial role in being able to recognize that traumatic event is taking place. Lastly, Allsop also touched on the fact that observational learning was more robust with prior experience – this too makes sense conceptually given prior experience could more easily recall that traumatic event. I think it would have been interesting to look at the hippocampus as this is technically still learning and how robust the projections from the BLA to hippocampus are in each context and group.
Overall, as we have discussed in class, while this may not lead to any treatments any time soon, any form of understanding we can gain from these papers helps us understand neuropsychological disorders. Especially in the context of PTSD, where the inciting incident for many victims has been questioned and criticized, I think these papers lend support to the fact that an individual does not need to undergo physical stress for PTSD to develop.
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