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Ryuji Takeya, Tetsuko Kasai; An early electrophysiological response associated with illusory contour processing is reduced by cognitive load. Journal of Vision 2014;14(10):801. doi: https://doi.org/10.1167/14.10.801.
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© ARVO (1962-2015); The Authors (2016-present)
It is known that figures with illusory contours (IC) evoke a specific electrophysiological response in comparison with control figures at around 110-200 ms after stimulus onset. Because previous studies have shown that this IC effect is equally observed regardless of ongoing perceptual tasks, it may reflect automatic perceptual processing of IC in visual cortical areas. However, it is still not clear whether the IC effect can be affected by cognitive task load, which is another possible factor to modulate visual processing. The present study examined this issue by using event-related potential (ERP). Method: IC and control figures were formed by using the arrangement of 4 packmen. The IC, control, and digit stimuli (1-9) were randomly presented (presentation ratio was 2:2:1). ERPs were recorded from 17 participants who were viewing the stimuli and simultaneously counting the number of digits (low-load task) or subtracting current digits from 400 (high-load task). Results: ERPs in response to the IC figure was observed to be more negative than those in response to the controls at 110-160 ms post-stimulus over the right occipital-temporal electrode sites. Importantly, this effect was found only for the low-load condition. ERPs in an earlier latency range (80-110 ms) did not differ by tasks or figures. Discussion: We identified an IC effect for the low-load condition, which was similar to that in the previous studies, while this effect was completely absent for the high-load condition. There was no difference in the earlier P1 latency, which suggests that cognitive load associated with calculations specifically affected IC processing without mediating lower-level visual processing or spatial attention. The present study shows that IC processing is not completely automatic and shares some processing resources with cognitive operations.
Meeting abstract presented at VSS 2014
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