光栅朝向分辨学习中存在关于45°对角线对称的镜像迁

Diagonal Mirror-Transfer in Perceptual Learning of Orientation Discrimination

采用光栅朝向分辨任务来探讨视知觉学习中是否存在关于45°对角线对称的镜像迁移现象。训练被试分辨15°或75°朝向3或5天，每天约1小时，训练前后测量15°、75°、45°朝向的分辨阈值。通过训练，训练朝向（15°或75°）的阈值下降，该学习效应没有迁移至45°朝向，但基本迁移到关于45°对称的朝向（75°或15°）上。这提示，视知觉学习可能发生在中间视皮层，该皮层同时具有一定的朝向特异性和关于45°对角线对称的镜像迁移性。

Adults’ ability to discriminate some basic features can be improved through training， which is referred to as perceptual learning. During recent years， perceptual learning has been investigated extensively in various visual tasks. In particular， studies on visual perceptual learning have reported mirror-transfer symmetrical about the vertical line. The present study aims to further investigate whether mirror-transfer symmetrical about the 45° diagonal line exists. The two-alternative forced-choice paradigm was applied to grating orientation discrimination task: two gratings of different orientations were presented successively， and subjects were required to decide whether the orientation of the second grating (test orientation) was clockwise or counterclockwise to that of the first one (reference orientation). There were three reference orientations， 15°， 45°， and 75° (15° and 75 ° are mirror orientations of each other about the 45° diagonal line). 11 subjects were trained with reference orientation of 15° or 75° for several days， and received threshold tests on all the three reference orientations both before and after the training. The two-up-one-down staircase procedure was adopted in threshold tests and training. The results showed that the threshold of trained orientation declined substantially after training. Such learning effect did not transfer to the 45° orientation which was 30° away from the trained orientation， but almost completely transferred to the mirror orientation which was 60° away. These results indicated that mirror–transfer symmetrical about the 45° diagonal line exists in visual perceptual learning of orientation discrimination. Diagonal mirror-transfer found in the present study suggests that visual perceptual learning of grating orientation discrimination might involve the intermediate visual cortex， which is characterized by both orientation selectivity and diagonal mirror transferability .