CRCNS: US-German Collaboration: Auditory and Spatial Sequence Encoding in the Hippocampus

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Complex cognitive functions such as spatial cognition, language development, and episodic memory require associations between multiple sensory experiences, such as images and sound, and require that associations are remembered in sequence. The rodent hippocampus has been one of the leading models for understanding neuronal mechanisms for remembering a sequence of spatial locations. Yet, it remains unknown whether the mechanisms that are used for encoding a path through space are the same as those that are used for encoding sequences that contain multiple modalities. To address this question, the auditory modality is of particular interest since it provides a mean to present a sequence of stimuli with high temporal precision and thus a mean to investigate time constraints for sequence learning. The proposed research investigates auditory sequence learning in a rodent species that is a hearing-specialist and tests whether the hippocampus of Mongolian gerbils can encode sequences of auditory stimuli with mechanisms similar to those used for spatial sequences. It will be tested whether place fields and theta phase precession exist in Mongolian gerbils, whether complex sound stimuli are encoded in the gerbil hippocampus in a spatially-independent manner or in association with the location of the animal, and whether sound sequences are encoded with network mechanisms related to those that are used for encoding spatial sequences. These questions will be addressed with single-unit recording from hippocampal principal cell populations of behaving animals, and experiments will be conducted in a virtual reality setup that allows for the precise delivery of auditory stimuli. Performing these experiments in a rodent species with an auditory specialization might result in important advances in addressing how the hippocampus encodes multimodal sequences. This research can provide important insight into neural network mechanisms for sequence coding and can lead to a better understanding of the contribution of the hippocampus to language development in humans.This project is jointly funded by Collaborative Research in Computational Neuroscience and the Office of International Science and Engineering. A companion project is being funded by the German Ministry of Education and Research (BMBF).