Cite as:
Smith S, Wenderoth P, van der Zwan R, 1999, "Transient and sustained components of orientation illusions" Perception 28 ECVP Abstract Supplement

Transient and sustained components of orientation illusions

S Smith, P Wenderoth, R van der Zwan

Orientation illusions which occur whenever a vertical (or horizontal) 1-D test grating is surrounded by another 1-D inducing grating can be shown to have opposing effects contingent on a number of stimulus parameters. These opposing effects have been claimed to result from different orientation-processing mechanisms. In particular, orientation-repulsion effects are thought to arise in V1 and are sensitive to spatial and temporal parameters, whereas orientation-attraction effects are held to arise in extrastriate cortex and are generally insensitive to such manipulations. When it was reported (Wolfe, 1984 Vision Research 24 1959 - 1964) that orientation-repulsion aftereffects occurred with short test flashes, Wolfe postulated that either there are distinct mechanisms which process brief and longer-duration stimuli; or that there are distinct mechanisms which do not primarily process duration but are differentially responsive to temporal parameters, amongst several others. We present data to suggest that large orientation-repulsion effects can be induced with stimulus parameters other than duration, including contrast and spatial frequency. The effect of these stimulus manipulations, however, are attenuated if the transient components of stimulus presentation are removed by means of a ramped increase in luminance contrast.

*Second address incomplete.

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