Ramirez: Now and Then

      One of the things that I found the most interesting between the 2013 and 2015 Ramirez et. al papers is that in the first paper, the "false memory" is created with negative stimuli, where as in the second paper, the dentate gyrus is activated with a positive stimuli. The fact that this subset of engram neurons can code for both positive and negative memories show how widespread their control of memory formation must be. I find it interesting that it seems that these neurons and their pathways are responsible for any kind of memory- not fear specifically. This is especially important to note because the two papers use very different kinds of tests in order to explore the behavioral outcomes of planting "false memories". The 2013 paper measures differences in freezing levels, where as the 2015 paper measured open field tests, elevated plus maze tests, tail suspension tests, and sucrose preference tests. Measuring freezing levels is generally regarded as a test of fear, but poor performance on the other tests from the 2015 paper are indicators of anxiety.

      Another piece of information I found interesting was that the 2015 paper examined the relationship between the dentate gyrus and the nucleus accumbens. They measured the effects of optically reactivating DG cells that were previously labeled by a positive experience in mice that were given a dopamine blockade or a glutamate blockade drug. This is similar to the previous papers which examined the effects of this blockade in the Nacc when the VTA dopamine neurons were manipulated. From that previous paper, we learned that dopamine receptor blockades in the Nacc can be very detrimental on the motor functions of a mouse. I am curious as to why the Ramirez group chose to pursue this route anyways, even when it had the potential to throw off results as a result of decreased motor functioning.