Central Processing of Electrosensory Information in MormyridFish

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Several fish species, besides the famous electric eel, are now known to have electric organs, and use weak electric organ discharges (EOD) for three main functions. Electrolocation is used both "actively" and "passively" much as a dolphin can use hearing for both echolocation and for passive listening, and variations in EOD are used for communication between individuals. The continual discharge produces an electric field of a particular shape around the fish, and the "mormyromast" class of receptors for "active" electrolocation detect deformations in this field. These signals are sent by afferent nerves to the mormyromast region of the electrosensory lateral-line lobe (ELL), in the midbrain. This project concentrates on characterizing the physiology and morphology of the different cell classes in this important area, where very little is now known. The ease of using external artificial electric stimuli means that many generalizable aspects of neural timing relations can be studied in this brain circuitry. Precise morphology in this region will be needed to understand how the anatomical local circuits contribute to the processing. The ELL has some similarity to the cerebellum, and may well reveal equally interesting mechanisms of timing and plasticity control. Results will be fundamental for understanding electrosensory mechanisms, and also will have important implications for general understanding of sensorimotor integration and neuronal processing.