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Shinichi Koyama, Alex Harner, Takeo Watanabe; Task-dependency of tuning characteristics change in the course of perceptual learning. Journal of Vision 2002;2(7):72. doi: 10.1167/2.7.72.
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© ARVO (1962-2015); The Authors (2016-present)
[Purpose] Last year in VSS, we reported that detection and discrimination learning might involve different mechanisms (Koyama et al. 2001). This year, using more sophisticated methods, we examined how attention changes tuning characteristics in each type of learning. [Methods] The subjects were divided into two groups. They participated in either coherent motion detection training or coherent motion direction discrimination training. In the detection training (n=5), subjects viewed two Newsome-type dynamic random dot displays successively and judged which of the two displays contained coherent motion (18% coherence). In the discrimination training (n=5), the subjects judged whether the directions of the coherent motion in two successively presented displays matched (difference of the two directions=20deg). Importantly, the same set of stimuli were used for both types of training with equal frequency. Before and after the training, the coherent motion detection thresholds were measured for nine directions including the trained directions. [Results] Surprisingly, the two groups showed opposite patterns of learning. The detection group showed more increase in sensitivity at the trained directions than untrained directions. In contrast, the discrimination group showed less increase in sensitivity at the trained directions than untrained directions. However, the pattern of learning became similar between the two groups when the two trained directions were separated by 90deg: in both groups sensitivity increase was greater at the trained directions than untrained directions. [Conclusions] Although both groups viewed the same stimuli equally often, they showed opposite patterns of improvement. These patterns of tuning characteristics changes may be explained by strong lateral inhibition of neighboring directions in the discrimination task but not in the detection task. The recent controversy as to the tuning pattern changes by attention may be explained by task demands.
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