When an animal moves around in its environment, the movement itself generates stimuli that can affect all the sensory systems. It is important for an animal to have some kind of adaptive mechanism to minimize this self-generated noise that can interfere with detecting important sensory signals in the external environment. This project uses the electrosensory system of an elasmobranch fish, the skate, to analyze the neural circuits in the brain that provide such mechanisms. Intracellular electrophysiological recording with dye labeling allows identification of relevant nerve cell responses during self-generated versus external stimuli. The mechanism for producing a differential cancellation of common input is explored by testing the role of known inhibitory transmitters on the cells involved. A novel approach here uses a weak external electrical signal in the water that is directly coupled to the timing of fin movement, which itself creates a signal detected by the electrosensory system. This paradigm allows direct tests for whether the adaptive filter mechanism works by an active process. Results will add an important comparative dimension to our understanding of electrosensory systems, and will have implications for issues of brain control of movement and sensation, which are fundamental for all neuroscience, with added relevance to robotics and artificial neural systems.
