Change in detection threshold caused by peripheral gratings: dependence on contrast and separation

The detection threshold for a sinusoidal grating in the presence of peripheral gratings was determined as a function of peripheral-grating contrast and separation between the two gratings, with phase relation as a parameter. The result showed that the peripheral gratings, in the range of low contrast, yielded a facilitatory or an inhibitory effect dependent on the phase relation, but in the range of high contrast, yielded an inhibitory effect irrespective of the phase relation. This suggests that two separate mechanisms may underlie the grating induction effect of the detection threshold.