The persistence of dichoptically presented grating patterns

A dichoptic viewing device was used to present sinusoidal gratings with interocular asynchrony. The persistence of various spatial frequencies was then determined psychophysically by using blank detection, for near-threshold and suprathreshold contrast conditions and across the contrast range. Greater persistence was evident for higher spatial frequencies, and across all spatial frequencies the values were higher for near-threshold contrast conditions. Contrast specificity was evident, with the low spatial frequencies showing flat contrast functions while the higher spatial frequencies showed a steeper monotonic curve. Intermediate spatial frequencies displayed biphasic properties. In view of the different neural persistence for different spatial frequencies, we investigated the degree of binocular summation for different interocular asynchronies. Binocular summation was predominant for all spatial frequencies where the dichoptic asynchrony was within 25 msec. Binocular summation decreased as a function of asynchrony. The binocular/monocular ratio decreased to a greater extent and earlier for low than for high spatial frequencies.