An Analog VLSI Model of the Fly Elementary Motion Detector

Part of Advances in Neural Information Processing Systems 10 (NIPS 1997)

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Reid Harrison, Christof Koch


Flies are capable of rapidly detecting and integrating visual motion in(cid:173) formation in behaviorly-relevant ways. The first stage of visual motion processing in flies is a retinotopic array of functional units known as el(cid:173) ementary motion detectors (EMDs). Several decades ago, Reichardt and colleagues developed a correlation-based model of motion detection that described the behavior of these neural circuits. We have implemented a variant of this model in a 2.0-JLm analog CMOS VLSI process. The re(cid:173) sult is a low-power, continuous-time analog circuit with integrated pho(cid:173) toreceptors that responds to motion in real time. The responses of the circuit to drifting sinusoidal gratings qualitatively resemble the temporal frequency response, spatial frequency response, and direction selectivity of motion-sensitive neurons observed in insects. In addition to its pos(cid:173) sible engineering applications, the circuit could potentially be used as a building block for constructing hardware models of higher-level insect motion integration.