Labeling memory neurons in Ramirez et al

The experiments carried out by Ramirez et al were very impressive. They were able to not only label but also activate small populations of neurons in the dentrate gyrus. To do this the group used c-fos mice expressing Channelrhodopsin-2 like we have seen in past experiments. The cool thing in this experiment was the use of doxycycline to control when and where the channelrhodopsin-2 was expressed. If animals were given doxycycline they were not able to express channelrhodopsin. Providing Dox in a novel environment could easily turn on this labeling. This was a very cool addition to the previous optogenetic studies. This allowed the group to look at small groups of neurons that were activated in different contexts. The level of detail and precision with which this protocol allows specific small populations of neurons to be labeled is very neat. Being able to look at which neurons are utilized for different contextual memories was pretty cool.

It was interesting that the false memories and genuine memories interacted with each other as shown in Figure 3. The artificially stimulated memories either competed with the genuine memories during acquisition, or they were additive. This also showed that the light activated memories were similar to the genuine memories. The way that the false memories and genuine memories interact is pretty neat because it touches on how distorted memories can arise in humans by adding misinformation on top of other memories. This ties in with human PTSD symptoms and memory modification. Past memories may be able to acquire new queues through the constructive or competitive interactions of different contextually derived memories.