Psychophysical Evidence for Spatial Channels

More than a decade of research spawned by the work of CAMPBELL and ROBSON [1] and GRAHAM and NACHMIAS [2] has led to a general consensus that the human visual system contains several different classes of spatial mechanisms or channels that process the retinal image in parallel. Thus, elucidation of the spatiotemporal filtering characteristics of these mechanisms has become one of the major tasks of psychophysics. In general, of course, it is to be expected that complex interactions will occur between mechanisms responding to neighboring portions of the retinal image; and we know this to be true for the processing of movement and depth information. Fortunately, experimental paradigms have been developed which have enabled us to estimate mechanism characteristics at a lower level than that at which these interactions occur. This article will focus on two of these techniques and the resulting characterization of human spatiotemporal mechanisms.

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