Abstract
The perceived direction of motion of a brief moving fine scale pattern reverses when a static coarse scale pattern is added to it (Henning & Derrington, VR, 1988). This impairment in motion direction discrimination has been explained by the inhibitory interaction between motion sensors tuned to fine and coarse scales. This interaction depends on the particular spatial frequencies mixed, the size of the stimulus, and the relative contrast of the components (Serrano-Pedraza et al., JoV, 2007, 2010, 2013). In this research we wanted to study the effect of speed on the interaction between motion sensors. We measured duration thresholds in a motion direction discrimination task using Bayesian staircases. The stimuli used in the experiment were horizontally drifting vertical-Gabor patches of 4 degrees diameter (2Sxy). Five stimulus configurations were used: 1 c/deg moving, 3 c/deg moving, 1 c/deg moving + 3 c/deg moving, 1 c/deg moving + 3 c/deg static, and 1c/deg static + 3 c/deg moving. We tested five speeds: 0.5, 1, 2, 4, and 8 deg/sec. Results show that for all conditions but 1c/deg static + 3 c/deg moving, duration thresholds decrease with increasing speed. However, in the condition 1 c/deg static + 3 c/deg moving, duration thresholds increase from 0.5 to 2 deg/sec and then reduce with increasing speed. When representing duration thresholds as a function of speed, our results show for the first time that the inhibitory interaction between motion sensors tuned to coarse and fine scales is tuned to speed showing a band-pass tuning function with a maximum between 1-2 deg/sec.
Meeting abstract presented at VSS 2017