Central Processing of Electrosensory Information in MormyridFish

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Certain fish are known as "weakly electric fish" because they have electric organs that generate a small repetitive discharge that creates an electric field in the surrounding water. The fish has electrosensory receptors in the skin which are able to detect the timing and the spatial distribution of the electrical field, and can use this information for sensing objects in the environment, and for communication. The first stage of central processing of the electrosensory information is a part of the brain called the electrosensory lateral-line lobe (ELL); this lobe has a cortical structure with a cellular organization similar to that found in the cerebellum. Other systems also project to the ELL, including sensory input from other systems such as mechanoreceptors of the lateral-line organ, signals descending from higher levels of the electrosensory system, and a particular set of signals called "corollary discharge" which occurs every time the electric orgal discharge occurs, and is believed to provide a reference signal useful to interpreting how the electrosensory input from the environment may be changed from the "expected" input. This project uses electrophysiological cellular recording and anatomical methods to complete a study of the cell types found in the ELL; to establish the major cell classes of the next higher central station called the pre-eminential nucleus, and how they project to the ELL; and to see whether the non-electrosensory inputs to the ELL can change depending on prior association with electrosensory input. Results from this work will be important for insights into the possible functions of central inputs that modulate incoming sensory signals, and in clarifying fundamental principles of functional circuitry in structures like the cerebellum.