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Bianca van Kemenade, Kiley Seymour, Marcus Rothkirch, Philipp Sterzer; Decoding pattern motion information in V1. Journal of Vision 2013;13(9):361. doi: 10.1167/13.9.361.
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© ARVO (1962-2015); The Authors (2016-present)
Two superimposed gratings moving in different directions can be perceived bound together in a pattern, moving in the average direction of the two gratings. This is referred to as pattern motion. It has been proposed that V1 processes the motion of the components, whereas pattern motion would be processed at higher levels of the visual hierarchy, especially in hMT+/V5. Using multivariate pattern analysis we investigated whether pattern motion is processed as early as in V1. We used stimuli composed of sinusoidal gratings, perceived as patterns, of which the angle between the gratings ranged from 30° to 120°. Two different pattern directions were used. Participants were presented with these stimuli in a pseudo-randomised block design, during which they had to perform a fixation task and a speed discrimination task. Eye tracking was performed to ensure proper fixation. Polar angle retinotopic mapping and a standard functional hMT+/V5 localiser were used to define ROIs. A classifier was trained to discriminate the two pattern directions. The classifier was able to decode the two pattern directions significantly above chance in all ROIs. Cross-classification was performed by training the classifier on a stimulus pair with a certain angle between the gratings, and testing the classifier on another stimulus pair with a different angle. Again, decoding accuracies were significantly above chance, and no significant differences between any of the performed cross-classifications were found in any of the ROIs including V1. This suggests the classifier did not use component motion signals, but more likely pattern motion information. Our results indicate that V1 contains pattern motion information. Whether this information is due to genuine pattern motion processing in V1 or to feedback from higher areas remains to be investigated.
Meeting abstract presented at VSS 2013
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