Contrast, spatial frequency and test duration effects on the tilt aftereffect: implications for underlying mechanisms.

The tilt aftereffect (TAE) was measured with a forced-choice technique for gratings of different spatial frequencies, contrasts and adapting and test durations. At short test durations, a 2 c/deg grating gave a larger TAE than a 10 c/deg, while at long test durations the opposite occurred. Low contrast gratings tended to give smaller TAEs at short test durations, and larger TAEs at long durations, than high contrast. A longer adapting duration tended to produce larger TAEs at low contrast for any test duration, but larger TAEs at high contrast only at long test durations. We suggest that the spatial frequency effect reflects differential excitation by the test stimuli of transient and sustained channels, and that the contrast effects reflect both a non-linearity in the relationship between excitation and inhibition, and the adapting effects of the test grating.