Abstract

The ratio of inhibition to excitation in visual re­sponse changes as a function of spatial frequency. The ratio varies from ~1.0 at low spatial frequencies to 0 by ~10 cycles/deg. Therefore, the effect of lateral inhibition on the shape of the contrast transducer function can be investigated by varying spatial frequency and masking contrast. We examined this hypothesis by presenting brief contrast increments in 0° phase to a steady back­ground grating having the same spatial frequency as the test grating. We explored the effects of spatial frequency across a 6-octave range, masking contrasts across a 7-octave range, and short and long stimulus durations on the contrast masking function. A 2 AFC procedure was used to measure the contrast threshold. The shape of the contrast transducer function derived from these data changed significantly as the spatial frequency of the test and background gratings varied from O. 25 to 20 cycles/deg. The results can be interpreted to imply that the contrast transducer pre­cedes the site of lateral inhibition.

© 1986 Optical Society of America