Neural activity in a hippocampus-like region of the teleost pallium are associated with navigation and active sensing

Neural mechanisms underlying spatial navigation in fish are unknown and little is known, for any vertebrate, about the relationship between active sensing and the formation of spatial maps. The weakly electric fish, Gymnotus Carapo, uses their active electric sense for spatial navigation. The electric organ discharge rate (EODr) undergoes transient increases during navigation to enhance electrosensory sampling. Gymnotus also uses stereotyped forward/ backward swimming as a second form of active sensing that brings objects towards the electroreceptor-dense head region. We wirelessly recorded neural activity from the pallium of freely swimming Gymnotus. Spiking activity was sparse and occurred only during swimming. Notably, some units exhibited significant place specificity and/or association with both forms of active sensing. Our results provide the first characterization of neural activity in a hippocampal-like region of a teleost fish brain and connects active sensing via sensory sampling rate and directed movements to higher order encoding of spatial information.