Week 4

These two papers present an interesting way to explain how memories are formed. The papers conclude that the neurons in the lateral amygdala (LA) with the highest excitability get preferentially recruited to become part of the memory trace for a fear memory. The authors show that this can be manipulated using viral and Optogenetic constructs to increase excitability. Interestingly, the reactivation of these LA neurons alone can cause behavioral effects associated with the memory. This leads me to believe that memories in the amygdala could be targeted and activated at will. Maybe this could be a way to treat depression, by activating positive memory engrams within the LA (as was suggested in last week’s paper). Alternatively, perhaps this will help us prevent the formation of traumatic memories. I read something about a drug that, when given to rape victims during a certain time frame after the rape, can help prevent the strength of the traumatic memory, in an effort to prevent the memories from affecting the victim’s life later on. Maybe the information learned about neuronal excitability could be used to decrease excitability in order to prevent a strong memory. Although, the authors show that the excitability needs to occur directly before training, so one could only potentially prevent a memory directly before it happened. Maybe this could be useful for soldiers going into battle to help prevent PTSD? Just some thoughts…

            I also found Yiu et al’s discussion of intrinsic excitability very interesting. One of the big questions I had after reading these papers was how neurons in vivo have different excitabilities and how this is dictated based on the memory being formed. I wonder whether different neurons will be primed to have increased excitability when a happy vs. a sad memory is taking place. Yiu et al mention that intrinsic excitability is regulated by learning, and that learning can increase excitability. This leads me to wonder whether different life experiences cause some people to “learn” to activate different neurons, which can lead to different formations of memories or perhaps a predisposition to see things in a positive or negative context when looking back at a memory. The authors also mention “preplay”, a theory that states that neuronal activity patterns occurring shortly before being exposed to a novel context can predict which hippocampal place cells fire. I’m not quite sure if I really understand what this means, but it sounds like the neuronal activity we have in our amygdala influences how we remember a new spatial context. That really makes sense to me if that can be generalized to mean that our emotions can influence how we remember a certain place, especially if we get exposed to something new in a bad or good mood. I would be really interested to read more about this theory.