Abstract
The mammalian hippocampal formation is essential for episodic memory and spatial navigation. Here, we seek to understand how information processing performed by individual neurons in one of the major output regions of the hippocampal formation, the subiculum, contributes to this function. The subiculum conveys information to a range of downstream regions, with these projections being organized along the proximal-distal axis. Yet, the functional consequences of this cellular heterogeneity remain a mystery. I hypothesize that this difference in connectivity allows subpopulations of subicular neurons to selectively route behaviorally relevant information to the hippocampus’ downstream regions. To test this hypothesis, I used anterograde and retrograde viral expression strategies to examine subpopulations of subicular neurons projecting to different downstream brain areas. I also visualized axons of these subicular neurons in an intact mouse brain using tissue-clearing techniques. This will allow future experiments to inhibit specific subicular neurons that project to a particular downstream region to study the behavioral effect of their activation. It will also enable researchers to use two-photon calcium imaging to map the activity of these neuronal subpopulations onto the learning performance of mice engaged in a spatial memory task. Together, these experiments will reveal how basic cellular properties endow subicular neurons with the ability to direct brain-wide neural circuit dynamics involved in learning.