PURPOSE: Increasing evidences are found that amblyopia is also associated with abnormal function of area relative to motion. We used bi-stable stimuli to explore if there is any different bi-stable perception between anisometropic amblyopia and nerotypical subjects. We considered that it should be a particularly useful probe to study the mechanisms of motion integration and segmentation, and help us to find unravel in more detail any deficit in the amblyopic visual motion system.
METHODS: The stimulus comprised two same rectangular-wave gratings presented through a circular aperture 7.7° in diameter on a middle-gray background, moved in directions 90° apart with the same speed. Contrast was defined in RGB units ( 30% and 5% ), with both gratings having the same parameters. The coherent motion direction were horizontal and vertical. Subjects were instructed to fixate the fixation point throughout the stimulus presentation (120 seconds), and report the percepts with two keyboard keys passively.
RESULTS: We found that there were no substantial differences in their perception of motion rivalry grating stimuli. With the contrast decreasing, these two groups performed different in details, such as the change in percept duration times, frequency of perceptual swithes. For the two percepts (coherent and transparent), the tendency of amblyopes and normal was totally oppositely. To horizontal and vertical motion direction, both amblyopes and normal have different perceptual switching frequency.
CONCLUSIONS: Althougth the global performance was normal in amblopes, their perceptual switching frequency, percepts duration time were both different from normal person, indicating their abnormal visual motion system. Due to the clearly contrast related effects, the higher SNR in amblopes might be a reasonable excuse. We also use the model simulation to fit our behavioral results, indicating the neuron adaptation, input strength and the reciprocal inhibition between coherent and transparent neuron populations were all differ from normal subjects.