Week 3 Papers

The Ramirez laboratory put out interesting works involving memory in the hippocampus and the ability to manipulate said memory. Their first paper back in 2013 describes a neural process of creating false memories that could impact the behavioral outcomes of rodents well removed from the memory event. The experimental design implemented was ideal in setting up a paradigm that allowed for the testing of multiple memory conditions and the additive or competitive interactions memories may have upon each other. The only fault that I found with the design was the Fig 3 B paradigm that included the novel D context. It seemed that the novel C context that the rodents were subjected to could have been utilized in place of the other D context since both contexts were novel and without any memory association. The experimenters could have easily just kept the design similar to that in Fig 2 A and had light on and off conditions for the C context. Besides this fact, I found the interference of memory was demonstrated particularly well with the light on and light off conditions in ChR2-mCherry light and no light mice. This paradigm showed that mice that had labeled cells from context A that were light activated during context B and again activated in context B' had an increase in freezing activity, showing the additive nature of their fear memories. While the mice that had labeled cells from context A that were not light activated during context B but were light activated in context B' showed a decrease in freezing activity, showing the competitive nature of memory. It was interesting that both subject groups overlapped during the light on condition in context B', suggesting that the activation of labeled cells from context A in the no light group may have mitigated the fear response of context B during the light activated phase. On the other hand this affect seemed to have been mirrored in the opposite manner in the light on group.
     The later paper from the Ramirez laboratory studied memory in a whole different way than the previous paper. Their usage of "positive experiences" in order to alleviate depressive behaviors was impressive. Although the alleviation of the depressive behaviors had no effect on the alleviate of the stress behaviors that the rodents were experiences, this chronic activation of "positive experience" memories seems like it could be an applicable way for human treatment of depressive states. The main outcome being that the VTA firing rates returned to normal after chronic stimulation and as seen from previous papers those firing rates may be the very reason that there are depressive behaviors in the first place. This knowledge could be utilized in a number of ways to create new targets for TMS that would hopefully activate these same engram cells and assist with depression relief.