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Although much progress has been made in describing the biophysical characteristics of single neurons, how they account for stimulus selectivity in higher order visual neurons remains poorly understood. The lobula giant movement detector, or LGMD, in the locust brain provides a favorable model system to investigate such questions. The LGMD is selectively activated by objects approaching on a collision course with the animal, or their two dimensional projections on a screen, called looming stimuli. Several biophysical mechanisms underlying this looming stimulus selectivity will be presented. In particular, spike frequency adaptation plays an important role by allowing the neuron to ''filter out'' visual stimuli that might otherwise activate it. |
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