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Post 4- Understanding the Memory Trace or Engram

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The two papers Han et al (2009) and Yiu et al (2014) both portray the importance of localization of memory trace within the brain. Han et al include an activated fear response and detect whether killing activated neurons removes memory of the experience. Death in neurons that overexpress CREB resulted in suppression of auditory fear memory. The neurons that overexpress CREB rather than the number of LA neurons affect this suppression. Furthermore, Yiu et al expands the model with multiple control experiments to add additional support to Han et al’s findings. In addition to the lateral amygdala (LA), they also test different regions (such as the central and basal amygdala). There were no significant differences nor memory enhancements with CREB overexpression in the other parts of the amygdala. Thereby, the findings appear to be specific to the LA in mice. 

The papers have provided further understanding to that neurons are a predominant factor to memory storage in our brains. It provides insight into a new way of understanding memory contrary to general psychological beliefs of how memory localization (engrams rather than large regions). Prior to reading these papers, I mainly thought of memory as relatively permanent in our brains, but with advanced techniques it appears to be possible to remove specific memories, especially in rodents. 

However, I believe that it would be beneficial if the researchers expanded their investigation to more brain areas that are known to encode memory. The amygdala is responsible for fear memories, but the hippocampus, cerebellum and prefrontal cortex are also responsible for memory functions of different forms. It would be interesting to see an extension of the investigation in response to memory engrams within the dentate gyrus or the cerebellum to gain further insight into the procedural or motor memories that mice may exhibit. Findings of memory engrams erased in these additional areas would be helpful in providing a greater comprehension of the initial process presented in the studies. Thus, it may be certain that fear conditioning would not deliver any significant findings in other parts of the brain, so these regions would therefore need a different conditioning/stimulus. What kinds of stimuli, similar to fear memory could instead be used when investigating other brain regions (apart from the amygdala), and their response to memory engrams? How likely is it that these findings will align with the ones of the two studies?

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