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Yuta Suzuki, Takahiro Shinkai, Hiroshi Higashi, Tetsuto Minami, Shigeki Nakauchi; Mismatch between perception and neural response in glare illusion. Journal of Vision 2016;16(12):819. doi: 10.1167/16.12.819.
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© 2017 Association for Research in Vision and Ophthalmology.
In the Glare illusion, brightness is boosted and even self-luminous impression is evoked, simply by surrounding luminance gradation. This study aims to investigate the underlying mechanisms by SSVEPs and psychophysics. We focused on the observation that luminance contrast of the flickering dots modulates SSVEP amplitude (Andersen et al., 2012). EEG experiment (Exp.1) was carried out to measure the SSVEPs evoked by the flickering dots displayed both on glare stimulus including luminance gradation (glare condition) and control patch surrounded by homogeneous luminance patches (control condition), with various luminance of the central region. Note that 2AFC experiment (Exp.2) confirmed the luminance enhancement in the glare condition. If the SSVEPs reflects the perceived contrast, larger amplitude is expected for the glare condition. However, obtained result was opposite: the SSVEPs was significantly lower compared with the control condition, especially for the high luminance contrasts stimuli. This suggests that the SSVEPs reflect neither physical nor perceived luminance contrast of the flickering dots. What factor can explain the reduction of the SSVEPs in the glare condition? We hypothesize that veiling reflection reduced the perceived contrast of the flickering dots and then SSVEPs decreased. To test the hypothesis, we measured the contrast threshold for detecting the flickering dots in both glare and control conditions (Exp.3). It turned out that the thresholds for both conditions showed no difference. We also measured the pupil responses to both conditions (Exp.4) and found that the pupil in the glare condition was significantly smaller than the control condition in high contrast. These results imply that the SSVEPs and the pupil responses to the glare stimuli reflects more cognitive factors, such as feeling of dazzling, rather than brightness perception. The cortical interactions between the early and the later visual areas may underlie for the modulation in the observed SSVEPs to the glare stimuli.
Meeting abstract presented at VSS 2016
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