Messing with Memory Engrams - Emily Jones

Both papers this week focused on memory engrams. Whether it was creating a false memory or activating neurons associated with memories, the two papers showed that there are specific neurons associated with specific memories. By finding and targeting these physical representations of a memory, researchers were able to induce a conditioned fear stimulus (Ramirez et al., 2013) and correct maladaptive behavior (Ramirez et al., 2015). Interestingly, it is even found in the latter paper than activating positive memories over a longer period of time produces longer lasting reversal of the maladaptive behaviors.
In the 2015 article, Ramirez and colleagues also investigated the effect of activating positive memory engrams on anxiety-like behaviors via open-field test and elevated plus maze test. They did not find changes in anxiety-like behavior. This negative finding makes sense especially in the context of our week 2 articles (Bessa et al., 2009, and Santarelli et al., 2003) on neurogenesis and neuronal remodeling in the hippocampal. In addition to the explanation provided by Ramirez’s team that anxiety-related behavior may rely more heavily on neurons involved in connecting the amygdala and hippocampus, the experiments done in this paper did not involve any physical alterations of the neurons themselves. As suggested by articles in week 2, physical changes in the neurons play a large role in rescuing stress-induced anxiety-like behaviors. This was not done in Ramirez et al. (2015), making an even stronger case for neurogenesis and neuronal remodeling.

It is no doubt that the techniques and findings in these two papers are amazing and exceptionally clever, but there is still a question to answer: how can this help humans? We currently cannot (ethically and technically) use this paradigm, or anything like it, on humans so what can we do next with these findings? In speculation, this is all a testament to the potential of Deep-Brain Stimulation (DBS) on alleviating depression symptoms. We could target specific neuron associated with positive memories in hopes of drowning out negative ones. We could relieve our happiest memories. This could help patients struggling with recurring negative thoughts and memories. However with current technology, it is unfortunately that DBS is not nearly specific enough for this is be a reality.

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