Optical illusions and their effect on attentional processes
Final Report Abstract
Overall, the present series of experiments investigated the functional mechanisms involved in generating perceived size representations and how these affect and interact with top-down processes. Our initial experiment (Experiment 1) directly addressed the role of perceived size changes on attentional orienting. This experiment revealed some counterintuitive results regarding the interaction between attention and perceived size changes and revealed general difficulties in disentangling lower level effects induced by illusion inducing figures and their effects on perceived size. Accordingly, a different paradigm was used which (Experiment 2) then allowed testing the temporal dynamics of context integration and the formation of perceived size. The results indicate that perceived size formation is fast (40 ms) and affects levels of processing that represent early stages of attentional processing involving saliency calculation. Several experiments using functional magnetic resonance imaging (fMRI) revealed that perceived size representations emerge from bi-directional interactions within a network consisting of bilateral ventral and right lateralized dorsal stream brain regions. Furthermore, our experiments suggest that the ventral stream regions, particularly V3v, play a major role in forming perceived size representations. In particular, we could demonstrate that left V3v is involved in integrating retinal size and distance information and that this brain area plays a key role in generating the moon illusion (Experiment 4). Furthermore, in an additional fMRI experiment using size-adaptation and a temporal version of the Ebbinghaus illusion we were able to separate visual activation related to the context that alters perceived size from those that are involved in size re-scaling (Experiment 5). This experiment provides direct behavioural and functional evidence for the presence of a neural bottleneck in rescaling retinal into perceived size, a process vital for visual perception. Functionally this bottleneck is found in left lingual gyrus, right supramarginal gyrus, and right superior parietal cortex. Finally, two experiments investigated the mechanisms underlying size-adaption as used in Experiment 5. The behavioural results indicate that the levels of processing underlying size adaptation are top-down penetrable and interact with top-down attention processes. The functional experiment performed has not yet been informative with regard to the functional mechanisms involved in this interaction between visual illusions and endogenous attention. Further experiments involving an improved experimental design are still needed.
Publications
- (2014) The moon illusion and size-distance scaling--evidence for shared neural patterns. Journal of cognitive neuroscience 26 (8) 1871–1882
Weidner, Ralph; Plewan, Thorsten; Chen, Qi; Buchner, Axel; Weiss, Peter H.; Fink, Gereon R.
(See online at https://doi.org/10.1162/jocn_a_00590) - (2012). The influence of stimulus duration on visual illusions and simple reaction time. Experimental Brain Research Nov;223(3):367-375
Plewan T., Weidner R., Fink G.R.
(See online at https://doi.org/10.1007/s00221-012-3265-7) - (2012). Ventral and dorsal stream interactions during the perception of the Müller-Lyer Illusion: Evidence derived from fMRI and DCM. Journal of Cognitive Neuroscience Oct;24(10):2015-2029
Plewan T.,Weidner R., Eickhoff S., Fink G.R.
(See online at https://doi.org/10.1162/jocn_a_00258) - (2015) Attention modulates visual size adaptation Journal of Vision 15(15), 10
Kreutzer S., Fink G. R., Weidner R.
(See online at https://doi.org/10.1167/15.15.10) - (2015) Rescaling retinal size into perceived size: evidence for an occipital and parietal bottleneck Journal of Cognitive Neuroscience 27(7):1334-1343
Kreutzer S., Weidner R., Fink G. R.
(See online at https://doi.org/10.1162/jocn_a_00784)
