Week 3

The Ramirez et al papers were incredibly interesting because of the unique cell labeling method and the fact that the false memory phenotype is so strong. While reading the first paper, I was wondering if this effect was specific to fear memories, and was super excited to see that they followed it up with a depression-related paper that showed this phenomenon extended to positive memories as well. The main question I’m now left with is what are these DG cells representing?

Are these place neurons that are specific to the place? Is it the memory of the image of the place? Is it a feeling associated with the place that can be experienced in combination with the fear that is associated with it later? I’m really fascinated by what these mice are experiencing when the A condition neurons are activated, and what that means for the depression-related rescue. If the mice could talk, would they be convinced that they had been in room A? Or would they say it felt like this was room A even though they could clearly see that it was another, distinct room? Maybe when they are in the room they can see that it is a different room but when they think back on the room they remember it as room A, and therefore the experience itself and the memory of it are completely separable.

Additionally, when the A-room neurons are being activated, are they themselves now encoding a positive sensation after going through the ‘positive experience,’ are new “positive feeling” neurons made in response, or are the A neurons activating some downstream neurons that are newly coded as “positive feeling.” Alternatively, are there neurons that are designated “positive feeling” neurons that already exist and that these place neurons form new connections with? I would think that positive memories as a whole would be stored in the hippocampus, but perhaps the positive  and memory part of positive memories are completely separable. The “positive” aspect of the positive memories could actually be stored somewhere else, like the NAc, such that the memory of the place and the positive feeling associated with it are actually stored in completely distinct palaces in the brain. In this case, many memories can be utilizing the same “positive feeling” cells which would be kind of strange, in a way, to think that we don't actually have any truly positive memories.

Maybe we only have memories, and positivity is overlaid on top of it almost artificially/superficially such that we could potentially overwrite many memories with positivity (or negativity based on the first paper). At first this seems possible, intuitive, and not that shocking, but this idea almost cheapens the memories knowing that there is nothing real about the happiness you remember feeling; positive feelings only exist in the moment those neurons are activated. In that sense, happiness really is fleeting.