10/17: Fear Memories

This week’s papers were both related to the effects of neuronal excitability on fear memory expression. Han et al., 2009 showed that increased CREB levels during fear learning are critical to the stability of that memory by deleting neurons showing overexpressed CREB levels, which blocked expression of fear memories by decreasing transgenic mice’s freezing levels. I thought the researchers did a very impressive job in finding the neurons in the LA that are actually involved in the fear learning process because instead of being in a small cluster they are widely spread out. There could have been more experiments in disrupting CREB, however, to further show that it is indeed involved.

Yiu et al., 2014 used the knowledge from the first paper to show that increasing neuronal excitability biases recruitment into the memory trace, enhancing memory formation. I thought this experiment was more comprehensive than the first one because they not only showed the involvement of CREB, but also numerous other molecules such as dnKCNQ2, hM3Dq + CNO, and ChR2 in neuronal excitability and memory formation enhancement. Furthermore, I like how they used Kir2.1 to show opposite effects in mice. They also used a wide-ranging set of control experiments, including the anxiety test and the anatomical specificity test.

From a clinical aspect, these experiments can be very valuable for the treatment of fear disorders such as PTSD. Clearly, these experiments are not exactly feasible in humans, but knowing that you can manipulate neurons in your lateral amygdala during fear memory expression is very important. These papers show that you need to excite neurons prior to training the fear memory, but perhaps researchers can next dive into ways you can manipulate fear memories after it has been encoded.