Electrosensory Processing of Plankton Capture in the Paddlefish Brain

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The proposed research will increase understanding of how the vertebrate brain processes sensory information and translates it into appropriate behaviors. A very unique animal and sensory mechanism is the subject of the project, the American paddlefish, which detects and captures its planktonic prey by sensing the weak electric signals from tiny water fleas. No other sensory modalities are necessary for successful feeding. The extremely small electric fields are detected by skin receptors and relayed to the posterior (primitive) region of the brain where they are processed and sent forward to the midbrain where motor commands are generated that govern swimming and feeding. This research will build on what is already known about how the paddlefish brain interprets electrical signals in terms of the physiological response properties of nerve cells in the hindbrain and their anatomical features in projecting to the midbrain. Dyes are microinjected into the brain that are transported along axons and dendrites of the cells, morphological features that constitute the wiring diagrams of the brain. Microelectrodes inserted into the brain allow the action potentials or spike activity of individual neurons to be recorded in response to sensory stimuli. Using these experimental procedures the current phase of the study will focus on how cells in the midbrain collect information from electrosensory and visual inputs, how individual cells come to represent complex features of the external environment, and the projection of these cells into the various processing centers (brain nuclei) of the hindbrain and spinal cord that activate the muscles triggering behavioral responses. This research has already had a significant impact on understanding the role of electrical signals, which humans do not experience, in paddlefish biology and corresponding conservation efforts. The study has also contributed to the research education and training of students in high school, college, and graduate school.