ABSTRACT
In order to investigate the interactions between first- and second-order motion perception systems, 14 adult subjects with normal or correct to normal visual acuity were recruited and divided into two groups. Then these two groups were trained, in their parafovea, to discriminate the direction of first- and second-order motion gratings respectively. The spatial frequency of the gratings used in study was fixed at 2 cycles/degree and the temporal frequency was fixed at 8 Hz during training. Contrast sensitivity of subjects in these two training groups for first- and second- order motion was measured before and after 7 days' training to estimate the effects of training. In addition, the differences between the two training groups(14 subjects) and another control group (11 subjects) were studied. The results showed that: 1) the training with first-order motion gratings can improve subjects' performance in first-order motion direction discrimination but the improvement can't be transferred to the performance in second-order motion task; 2) the training with second-order motion gratings can improve subjects' performance in both first- and second-order motion direction discrimination tasks. In conclusion, an " asymmetric transfer" occurred between the training effect of first- and second-order motion gratings. These results indicate that there are two mechanisms for perceiving first- and second-order motion respectively. However, they are not completely different from each other but only partly separated.