Decoding pattern motion information in V1 B van Kemenade1, K Seymour2, T Christophel3, M Rothkirch4, P Sterzer5 |
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1Berlin School of Mind and Brain, Humboldt Universität zu Berlin, Germany |
| Two superimposed drifting gratings can be perceived as two overlapping gratings or as a pattern. Previous studies have found pattern motion processing only from V2 onwards. Using multivariate pattern analysis we investigated whether pattern motion is processed as early as in V1. In experiment 1, we presented superimposed sinusoidal gratings with varying angles, perceived as patterns moving in two different directions. Participants performed a fixation task and a speed discrimination task. Eye tracking was performed to ensure proper fixation. Polar angle retinotopic mapping and a functional hMT+/V5 localiser were used to define regions of interest (ROIs). A classifier was trained to discriminate the two pattern directions. We could decode the two pattern directions significantly above chance in all ROIs. Cross-classification was performed between stimulus pairs with different angles. Again, decoding accuracies were significantly above chance, and did not differ between any of the cross-classifications in any of the ROIs. This suggests the classifier did not use component motion signals, but pattern motion information. This conclusion was verified by experiment 2, where we manipulated the perception of square wave gratings to yield either pattern or component motion perception. Our results indicate that pattern motion information is present already in V1. |
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