Hippocampal-dependent spatial memory encoding during attentive processing from place

Project Summary / Abstract Spatial memory is a core competency necessary for healthy independent living and for animal survival. While the hippocampus is well-established to be necessary for spatial memory, it remains poorly understood when and what the hippocampus does to support spatial memory. Studies of hippocampal function in rodents have focused predominantly on epochs of locomotion and quiet rest. Minimal attention has been given to the ubiquitously observed non-locomotor exploratory behavior of rearing onto the hind legs (rearing for short). Rearing occurs most frequently in novel environments, correlates with environmental learning, and engages rhythmic processing in the hippocampus. Yet, it remains untested whether epochs of rearing are necessary for spatial memory performance and what updates to the neuronal population code result from rearing. This project will address these gaps with new empirical experiments. Our focus on rearing is motivated by our new preliminary data showing that inhibiting the dorsal hippocampus selectively during rearing impairs spatial memory. Aim 1 will establish the importance of rearing as an epoch of hippocampal dependent spatial memory encoding in relation to other well-studied behavioral epochs. We will accomplish this through closed-loop optogenetic modulation of hippocampal activity and behavioral analysis in rats. Aim 2 will test the hypothesis that rearing supports error correction of spatial coding in the hippocampus. This will be accomplished through chronically implanted arrays of independently movable tetrodes in freely behaving rats. By the completion of these aims, this project will advance our mechanistic understanding of spatial memory and for our understanding of rearing as an epoch of mnemonic encoding. If successful, these results will lay the foundation for an R01-level program of research investigating the mechanistic basis of the rearing-mediated learning effect and the relevance of rearing-mediated learning for memory disorders and mental health.