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Paper Response #5: Sial 2016 and Allsop 2018

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WEEK 7: Feb. 24 Papers (Sial et. al, Allsop et. al)

Sial et al’s 2016 paper describes a new experimental paradigm that can be used to induce stress in mice in a laboratory setting in order to study the neurobiological intricacies of stress and stress-related disorders such as PTSD. Importantly, this new Vicarious Social Defeat Stress (VSDS) paradigm includes a witness component where one mouse witnesses another mouse go through a traumatic event (physical stress) but does not experience physical stress itself. The study found that witness mice will still become emotionally stressed and express symptoms such as social avoidance and other anxiety-like behaviors after watching another mouse be physically attacked The VSDS paradigm is used to differentiate between physical and emotional stress and is a key development in the study of PTSD, as this disorder can be developed after simply witnessing a traumatic event without the need to have been directly involved in it. I think this new paradigm is a very interesting and necessary experimental development, as many of the other papers we have read throughout the semester have not made much of an effort to differentiate between several mental illnesses such as depression, anxiety, and PTSD that are distinct from one another despite having overlapping symptoms. Increasing specificity in the study of mental illnesses can only be beneficial in furthering our understanding of them, and crucial information regarding the neurobiological mechanisms behind these disorders may be uncovered by paying greater attention to the details that differentiate their respective symptomologies. 

Allsop et al’s 2018 paper examines the neuronal connections that underlie observational learning and socially derived information. The study shows that innervation from the Anterior Cingulate Cortex (ACC) to the Basolateral Amygdala (BLA) is essential for encoding information learned from observing others, including observational fear conditioning. This paper ties really nicely into the Sial paper, as it provides more specific insight into the neurobiological mechanisms responsible for encoding fear information for the witness mice in Sial’s study. The Allsop paper compliments the Sial paper and provides some answers as to how witnessing a traumatic event leads to emotional stress on a neuronal level, or at least the very first steps in that process. It is not unreasonable to say that a gap remains to be bridged between the initial observational learning driven by ACC innervation to the BLA and this resulting in lasting emotional stress. What other brain regions and neuronal signalling pathways are involved in this process?

Furthermore, the Allsop paper discussed how prior experience leads to more robust observational learning, which was not something the Sial paper touched upon. It would be interesting to see if previous experience would also predict greater emotional stress in witness mice in the VSDS paradigm. However, this may complicate the mapping of these findings to real-life clinical cases in which a witness to a traumatic event develops PTSD despite not having any present or previous experience with the given trauma themselves. I’m unfamiliar with any research that may have been conducted into whether a person is more likely to develop PTSD after witnessing an event if they have previous experience with related trauma. 

Lastly, the results from Allsop’s study can also be more broadly applied to other psychiatric conditions beyond PTSD that involve social observation and learning, such as autism and social anxiety. Despite earlier praising the increased specificity of the VSDS paradigm in studying PTSD, there are also benefits to be reaped from uncovering basic neurobiological pathways like the one in Allsop’s study that can open many new avenues of research into a broader range of clinical disorders. 

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