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Chia-huei Tseng, Yating Huang; Eye-dependent attentional modulation on motion sensitization from speed discrimination. Journal of Vision 2008;8(6):1127. doi: 10.1167/8.6.1127.
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Tseng et al (2006) found that (1) human motion sensitivity improved after one-week speed discrimination training and (2) attention modulated this improvement. Here we investigated if the learning effect and attentional modulation are eye-specific. Our experiments contain three parts: pre-test, training, and post-test. During pre-test and post-test stages, observers view monocularly white dots containing 5%–50% moving coherence, and we obtained observers' 75% coherence threshold in eight directions for each eye. Exp. 1 During learning stage, we presented (to the right eye only) a display with uni-direction moving dots containing a speed change event, and observers learned to discriminate speed increase from decrease hourly for 7 days on average. We found moderate sensitivity improvements towards all eight directions in the right eye, and a smaller improvement (60% of what observed in the right eye) in the left eye. Further analysis shows the improvement is not due to behavioral criterion shift. This interocular learning effect lasted for at least two weeks, indicating a long-persistent change in neural plasticity. Exp. 2 To manipulate attention, we presented the same uni-direction motion stimuli (0 deg) to observers' right eye while to the left eye we presented similar dots moving at 90 deg. Perceptually, observers perceive a bivectorial transparent dot motion, and selective attention to the component motion with speed change is required to successfully detect the speed change. Attention generated a direction-selective sensitivity enhancement, and this modulation is restricted to the right eye only. In left eye, an overall sensitivity increase across all directions from interocular transfer is observed. Conclusion: We demonstrated a long-term motion sensitization induced by a motion speed task. This sensitization transfers between eyes in all directions, and persists for weeks. Direction-specific modulation on sensitization from attention is found to be eye-dependent.
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