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Post 5: Observational fear learning and its underlying neural circuitry

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Animals can learn and experience fear by observation in their environments. Especially in humans, not all situations of trauma have to do with a direct physical stress but also an emotional component, which might stem from observation. Sial et al. aims to establish a model that untangles direct physical fear experience from emotional fear by placing mice in an observational position to fear. It is seen that even in this emotional stress model that corticosterone levels and anxiety-related behaviors are upregulated even in re-exposure after one month. It is interesting to consider the reason for this observational fear to have such a profound effect on the mice as it might be an evolutionary mechanism in which either is a feeling of helplessness in being able to help out a fellow specie or an interoceptive pain response or conditioning that happens through observation. If the true underpinnings of such response could be further parsed out, this could have far-reaching implications in formulating studies to assist those with human PTSD by understanding the mechanisms behind the root of their trauma. Both situations are very real scenarios in which can cause significant trauma. 
            Allsop et al., examines the neural circuitry underlying observational fear learning to find that ACC neurons that project to the baso-lateral amygdala preferentially encode these situations and are necessary to respond only to observed fear but not direct physical fear. Interestingly, when these ACC->BLA neurons were inhibited only during the observational conditioning did the freezing response decrease when cued. Therefore, this truly reinforces that this circuit is responsible and could definitely become a therapeutic target for subtypes of trauma-related conditions. A very interesting observation made was that prior experience with the stressor was needed in this study in order for the observational learning to be affective. It would be good to study other types of stressors such as restraint or forced swimming in order to see if prior experience is still needed. If so, this is intriguing as then observational learning does require a mechanism including memory feedback to recognize another mouse’s fear or pain.

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