THE COMBINATION OF FILTERS IN EARLY SPATIAL VISION - A RETROSPECTIVE ANALYSIS OF THE MIRAGE MODEL

Since the discovery of spatial-frequency-tuned channels in the visual system, most theories attempting to account for pattern encoding have assumed that the filters can be independently accessed and flexibly co mbined. We review here an alternative model, 'MIRAGE', in which the fi lters are inflexibly combined before pattern analysis. In the MIRAGE m odel the half-wave rectified outputs of all spatial-frequency channels are combined before locating spatial zero-bounded regions in the neur al image, which serve as the spatial primitives for pattern analysis. We describe the evidence that led to this model, and review recent evi dence on the rules of filter combination.