Memory traces critical for auditory fear - Vasco Diogo


The two articles this week investigated the function and characteristics of memory neural traces in the amygdala of rodent brains. In the first article (Han et. al, 2009), targeted overexpression of CREB in the lateral amygdala was shown to strengthen a weak auditory fear memory. Furthermore, ablation of that memory trace in the LA resulted in loss of that fear memory, demonstrating the critical role of that neural trace for the memory to be recalled. The authors effectively demonstrated the trace is created specifically for that memory and that long term, specific amnesia can be induced for that memory by ablating the trace.

In the second study (Yiu et. al, 2014) the mechanism by which the neurons in the LA are selected for a memory trace was further investigated. From the previous evidence, it was known that increased CREB expression is an important factor in selection. Here, the authors looking to a specific CREB effect, higher excitability, to see if preferential selection to the neural trace could be attributed to that. Using 3 methods – dominant negative K+ channels, DREAAD, and optogenetics. The data show that neural excitability increases likelihood of allocation of a neuron to a memory trace. Importantly, exciting the neural trace was sufficient to induce partial recall of the memory, showing once again the central, critical role of the trace.

Some missing details in this article would present interesting lines of research for the future. Although the authors looked at the anatomical specificity of the effects of CREB, they did not do the same for the other three methods, which would have been important, as CREB is not responsible for neural excitability only – looking at the specific effects of neural excitability on neural trace neuron selection in the other amygdalar nuclei would be of primary interest. Furthermore, it would have been interesting to see the effects of Kir2.1 on the anxiety paradigms to probe for potentially anxiolytic effects of this channel in the LA.

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