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The Contribution of human brain areas to visual illusory effects: an fMRI-study on the illusory motion effect in the Pinna - Brelstaff figure

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  • M-Psi/01 Psicologia Generale
  • Design


In the Pinna - Brelstaff figure (PBF) an illusion of counter-rotating motion in two circles occurs when static patterns with specific luminance gradients are moved across the peripheral visual field during observer's self-movement towards or away from the figure. To create an illusion suitable for the MR scanner, computerised animation generated contraction and expansion of concentric circles of the PBF patterns on a screen. The visual illusory effect was quantified in each participant by nulling the illusory rotation effect in the PBF with counter-rotating motion. From these motion parameters correctly perceived rotating figures and a subjectively non-rotating PBF were created as a control individually for each subject. Sixteen volunteers with normal vision were tested at 3 T. A block design with randomised presentation order and full brain coverage EPI (1.7 mm × 1.7 mm × 3 mm resolution) was used. Both the illusory and the true rotation evoked increased activation within the motion-specific complex hMT+. The frontal eye fields and the Brocca homologue were found to be related to illusory rotation perception. When the real-stimulus-driven correct perception was compared with the illusory effect perception activations were found in the early visual areas, V1/V2.

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