Yui and Ramirez

These papers focus largely on the creation of memories. Ramirez et. al (2013) focus on the creation of a false memory in the dentate gyrus while Yiu et. al (2014) set out to prove that neurons with increased excitability are more likely to be involved in memory formation. Both papers ran extensive tests and covered a lot of information – they included a lot of different tests and anticipated a lot of other potential questions stemming from the core studies in the papers. I thought both papers were interesting also because the progression of the research involved was similar to what I would have expected.

Ramirez et. al (2013) do several tests that show that if neurons from a context A are activated during a context B when animals are both foot shocked and optogenetically triggered, the animal will express an increase in fear behavior when placed back in context A – essentially creating a false fear memory. They also placed the animals in novel contexts and were able to trigger these same levels of increased fear behavior by triggering ChR2 activation, creating an entirely false fear memory. After Ramirez et. al (2013) demonstrate that this is possible, Yiu et. al (2014) dig deeper into how these neurons are triggered, and look to prove that increasing excitability of a specific neuron increases the likelihood that the neuron will become part of the memory trace.

I particularly enjoyed the Ramirez et. al (2013) paper because they included several different combinations of contexts and showed that activation of neurons from the original context A can be triggered in other, completely different contexts. For example, in figure 3B they show that turning the light on was able to induce significantly higher levels of freezing in animals that had been fear conditioned in a light on context. I thought that this was interesting because it definitively showed that mice in the ChR2 condition with light had increased freezing behavior in the brand new context D when the neurons labeled in context A were activated.

Overall, I thought both papers were very convincing and provided ample support for their claims. However, I don’t see much application in humans for their methods – the procedures would probably be too invasive, and very difficult to test in live patients.