To achieve our objectives, we manipulated the activity of neurons connecting the RSC and the LD at the long-term recall of contextual fear memory. Briefly, we trained mice to associate a context with a negative experience, and then they are subjected to the same context without the negative stimulus 28 days later. During this period, we implanted optic fibers into their brains to manipulate the activity of their neurons with light, using a technique called “optogenetics”. We found that mice do retrieve this memory by assessing their “freezing” behavior, a well-established behavioral parameter associated to fear. Using a combination of free available and custom software we scored this behavior in an automatic and unbiased manner.
To study the kind of information the LD – RSC is processing, we also visualized and recorded the activity of neurons from both nuclei in mice performing contextual fear conditioning. We managed to extract data from hundreds of individual neurons and we implemented in-house analysis pipelines to find head direction cells. For this objective we also introduced a variation in the behavioral paradigm: we train mice in one context as mentioned above and assess the memory at recent (1 day after training) and remote (21 days) in the same context (A), but also in a different one (B). By doing this we found that, at recent recall, mice do freeze much more in context A, in which they were trained, and significantly less in the context B; Conversely, at a remote time point, mice do freeze to the same level in both contexts. This suggests there is a strong generalization effect over time. Furthermore, preliminary analysis show there is a portion of mice able to distinguish between contexts (“discriminators”), while other cannot (“generalizers”). The latter opens the opportunity to compare neuronal activity also between these two populations.
Preliminary results of these tasks as well as proofs of progress had been presented at internal seminars and scientific meetings. A more complete set of results is expected to be presented in a poster at Neuroscience Annual Meeting in November this year.
