Neural correlates of local and global characteristics in the Fraser illusion X Yun1, S Hazenberg1, R van Lier1, J Qiu2 |
|---|
1Donders Institute, Radboud University Nijmegen, Netherlands |
| Event-related brain potentials (ERPs) were used to examine the neural correlates of the Fraser illusion [Fraser, 1908; British Journal of Psychology, 1904-1920 (2), 307–320]. The studied Fraser illusion consists of black and white twisted cords on a chromatic patchwork background, where the concentric circles appear as a single spiral. Since the twisted cords (local orientations) and concentric circles (global configuration) contribute differently to the spiral illusion, we designed three additional variants by changing the local orientations, from twisted to parallel cords, and by changing the global configuration, from concentric to spiral circles, separately. Results of behavioral ‘concentric’ versus ‘spiral’ judgments in the four conditions showed that the local orientations dominated the illusory appearance. That is, for the displays with twisted cords an illusory appearance was most evident. We compared the ERP grand average waveforms of illusion and non-illusion responses over all conditions. When an illusory percept was reported we found a more positive component between 225-275 ms at the posterior scalp. We discuss the potential influence of local and global features on the neural mechanism of this illusion. |
| Up Home |
|---|