Week 5

I had a lot of issues with the Harry et al. 2008 paper. While it is most likely a function of my lack of knowledge of fear/fear research, I still felt myself feeling as though this paper didn't really address anything novel. First and foremost, while I am convinced that different neurons are activated during a fear or extinction behavior, I thought their results did NOT address "the question of whether individual extinction neurons can function as fear neurons for another CS". I do not think that two CS's would be enough to answer the question. Of course the fear neurons activated during CS2 weren't activated during the extinct CS1, and vise versa - but there could be plausibly hundreds of fear memories in a life time and how is this evidence to suggest that an extinction neuron for CSX couldn't be a fear neuron for CSY? While later in the paper their morphological and connectivity data do lend weight to the distinction of individual neuronal populations for the two behaviors, their CS1/CS2 data was week. While perhaps out of reach then (and maybe even out of reach now, I'm not sure), to lock down this idea they could have used this paradigm to identify the extinction neurons for one CS and see if activating them during a different fear CS could program a fear response.

Additionally in regards to the first paper, I was confused as to the significance of the findings presented in the "Rapid reversal of activity during fear renewal" section. It was my understanding that extinction takes place in the same context as the fear conditioning, and in this way one can be assured that the memory is actually "extinct" and they aren't just associating the tone in a safer context. I'm not understanding how one can claim the fear is extinguished if putting them back in the fear conditioning context causes the fear response to return. I believe this issue with the paper is more due to lack of understanding of the fear/extinction paradigm however.

All in all I definitely appreciated the connectivity data presented in the Harry et. al 2008 paper. I thought that showing that these specific neurons which are activated in a distinct behavior (that is mutually exclusive with the other behavior/set of neurons) have differential connectivity strengthen every other aspect of their results, as merely showing a physiological difference made the dichotomy of two populations much more plausible.