Sensory processing involves how nerve cells handle a sequence of signals with particular timing features. Often there are populations of neurons that act as filters, selectively responding only to signal trains with particular frequencies. The brain of weakly electric fish provides a model system for studying these temporal filters. Some weakly electric fish emit a small electric discharge at a highly regular frequency, and they have an electrosensory system that shows high sensitivity to any changes in the electrical pattern in the water. When a neighboring fish comes near, using a slightly different discharge frequency, both fish show a 'jamming-avoidance response' in which each fish shifts its own discharge frequency away from that of the neighbor, to avoid signal 'jamming' and allow easier reception of its own signal. This project uses a novel technique of recording single cell activity in a part of the midbrain called the torus, while giving precise signal frequencies to the electrosensory system. Physiological measures such as the variable conductances of the cell membrane will be analyzed to see how temporal filtering can be enhanced by a frequency-dependent mechanism of gain control for the incoming signals. Results will have a major impact because they will clarify one of the few cases where cellular membrane properties produce selectivity for temporally varying behaviorally relevant stimuli. The impact will extend across all sensory neuroscience, and also to a better understanding of central brain mechanisms.
