Movement detection: Performance of a wide-field element in the visual system of the blowfly

Abstract Action potentials evoked by stepwise or continuously moving visual patterns have been recorded extracellularly from the movement detectors in the lobula complex of the blowfly. Careful exploration of the receptive field with a spatially small stimulus shows that comparison of neural signals stemming from neighbouring visual inputs at the entrance site of the detector occurs. Further exploration with a spatially large stimulus reveals that the sampling of the visual environment is performed by a mosaic of pairs of visual inputs separated from each other by the interommatidial angle Δϕ. As a consequence of these results the applicability of the principles of the correlation model (based on behavioural optomotor experiments by Reichardt and Hassenstein) is investigated. It is shown that this model describes and predicts the performance of this neural element in a convincing way.