Abstract
The direction discrimination of a moving high spatial frequency pattern is impaired when a static low frequency pattern is added to it. This impairment has been explained by a motion sensing model that included an inhibitory interaction between motion sensors tuned to high and low spatial frequencies (Serrano-Pedraza et al., 2007). The strength of the impairment (i.e. strength of the interaction) is higher at short durations and is unaffected by dichoptic, monocular and binocular presentations (Derrington et al., 1993). Obtaining this impairment at short durations under dichoptic presentation suggests that the interaction is happening after binocular combination. However, this viewing condition has not been tested at long durations. Here, we conducted two motion cancellation experiments to measure the strength of the interaction under binocular, monocular and dichoptic presentations. In the first experiment, we determined the contrast needed to cancel the direction discrimination of a low frequency flickering Gabor patch (1 c/deg at 4 Hz) added to a drifting high frequency patch (3 c/deg at 4 deg/sec) at two durations (200 and 400 msec). Binocular and monocular presentations showed a strong interaction, while dichoptic presentations only produced a weak effect. The second experiment consisted of estimating the speed of a low frequency Gabor patch (1 c/deg) needed to cancel its perceived motion when added to a moving high frequency grating (3 c/deg at 4 deg/sec). We used two durations (140 and 280 msec) and results showed that there was no interaction for dichoptic presentations, independently of the tested stimulus duration. These results suggest that, for dichoptic presentations, there must be a critical duration in order to get an interaction between motion sensors tuned to coarse and fine features.