week 4: han and yiu

This week’s two papers both effectively proved that a fear memory could be created and then deleted successfully. My first question when reading only the title of the Han et. Al article was how is it possible to just delete a memory? Could they simply be extinguishing the memory through fear extinction by a declining response to the conditioned stimulus? But fear extinction takes time whereas this article was able to delete a memory directly after it was formed. To me that is simply incredible! What I appreciated most about Han et. Al’s paper was that they covered all their bases for proving that higher levels of CREB were recruited in the fear memory trace and that the ablation of these neurons therefore deleted the fear memory trace. First they tested that neurons with high levels of CREB were more likely to be activated than neighboring neurons without CREB after fear memory training. After, they wanted to make sure they were able to successfully kill these neurons by using diphtheria toxin (DT) in cre recombinase infected neurons, which induce did induce cell death. Then, they tested if killing the neurons expressing high levels of CREB that previously enhanced fear memory would then reverse this enhanced expression, and it did. To me this article had a great experimental design covering all of their bases and testing for things that would disprove their results. I was wondering at the end of the paper why they didn’t test for this CREB enhancement in other parts of the brain that are known for fear memory like the hippocampus that we saw in the last week’s papers. They even state that fear learning can encompass a broader region then that what was tested and affected by their treatment. All in all, I think Han et. Al’s paper set up a great foundation for Yiu et. Al’s paper. The second article had a very similar overall experimental design that also covered what else could be affecting their results and ruled it out. The one thing that I appreciated the most out of Yiu et. Al’s paper was that they tested the use of optogenetics on enhancing memory formation and neural activity. I thought this was very interesting to test for especially since we saw what great use it was in last weeks paper for creating a fake memory. If optogenetics could create a fake memory why couldn’t it be used to enhance the formation of a fear memory.