其他摘要 | The images of an object projected to left and right retina have a slight horizontal difference in viewing angle due to the horizontal separation of positions between two eyes. This difference is called binocular disparity. Binocular disparity is the most important clue source for stereopsis, which is crucial for creatures living in a three- dimensional world. Previous behavioral-based studies found that perceptual learning can significantly improve stereoscopic function. However, previous studies have debated the plasticity of binocular disparity perception learning, and its mechanism is unclear. Focusing on the plasticity mechanism of binocular disparity, this study combined psychophysics, ERP, and fMRI techniques to first systematically investigate the similarities and differences in characteristics of stereoscopic perceptual learning under different types of binocular disparity.
Study 1 investigated the incidence of stereoanomaly / stereoblindness in domestic adults with normal visual function under different disparity conditions. A total of 121 subjects were recruited, and random-dot stereograms (RDS) of different disparity conditions were used as stimuli to examine their stereopsis under different disparity conditions, and standard tests were also used. It was found that 1.27% of the subjects failed to demonstrate stereoscopic function in any of the tests, and may have stereoblindness.
Study 2 used RDS with different disparity conditions as stimuli, and conducted stereoscopic perceptual training on the subjects respectively, and investigated the characteristics of binocular disparity perceptual learning. In the second experiment, 40 subjects were randomly divided into four groups, one of which was the control group, and the other three groups received stereoscopic training under the conditions of zero- order, first-order and second-order disparity respectively. The results showed that the disparity thresholds were significantly decreased under the three training conditions. The transfer of learning effect has a certain asymmetry, which is, the training effect of the higher-order disparity condition can be completely transferred to the lower-order disparity conditions. Still, the learning effect of lower-order disparity conditions is only partially transferable to higher-order disparity conditions. It is suggested that the learning sites of different types of disparity processing may be different.
Study 3 used ERP and fMRI to explore the neural mechanism behind binocular disparity perceptual learning. Experiment 3 used ERP to investigate the neural mechanism behind binocular disparity perceptual learning and explore the ERP waveform changes to different disparity stimuli before and after the zero-order and second-order disparity training. A total of 20 subjects were recruited and randomly divided into two groups to receive stereoscopic training under zero-order and second- order disparity conditions, respectively. Their EEG signals were recorded before and after training. Under the zero-order training condition, the training only brought about changes in the peak value of the N1 component at the position of the parieto-occipital and occipital electrodes, and the peak value was significantly increased only under the zero-order disparity condition. Under the second-order disparity training condition, the peak value of the N1 component increased at the parietal, parieto-occipital, and occipital electrode positions under two disparity conditions; at the parietal electrode positions, the second-order disparity training also brought about changes in the P2 component.
In experiment 4, fMRI technology was used to investigate the changes in cerebral cortex activation before and after binocular disparity training. A total of 18 subjects were recruited and randomly divided into two groups to receive stereoscopic perceptual training under zero-order and second-order disparity conditions, respectively, and MRI scans before and after training. The results showed that under the zero-order disparity training condition, perceptual learning did not significantly change the activation state of stereopsis-related brain regions, and only the activation of the cingulate cortex and some prefrontal regions decreased. The second-order disparity training significantly improved the activation strength of some temporal and parietal areas and at the same time, increased the activation strength of some secondary visual cortex under the zero-order disparity condition. |
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