A comparison of pedestal effects in first- and second-order patterns

Pi Chun Huang, Chien Chung Chen

研究成果: Article同行評審

1 引文 斯高帕斯(Scopus)


The human visual system is sensitive to both luminance (first-order) and contrast (second-order) modulations in an image. A linear-nonlinear-linear model is commonly used to explain visual processing of second-order patterns. Here we used a pattern-masking paradigm to compare first-order and second-order visual mechanisms and to characterize the nonlinear properties underlying them. The carriers were either a high-frequency horizontal grating (8 c/°) or a binary random dot pattern; they were either added to a vertical low-frequency (2 c/°) sinusoidal grating (firstorder stimuli) or multiplied by it (second-order stimuli). The incremental discrimination threshold of the target was measured with pedestals whose spatial properties matched those of the target, with the exception of contrast (in the first-order pedestal) or modulation depth (in the second-order pedestal). The threshold function showed a typical dipper shape for both firstand second-order stimuli. The results for the first-order stimuli with different types of carrier and the secondorder stimuli with a grating carrier were well explained by a divisive inhibition model in which the facilitatory input was divided by the sum of broadband inhibitory inputs. The results for the second-order stimuli with a random-dot carrier were explained by a modified divisive inhibition model that operated on modulation depth. Our results suggest that divisive inhibition is required to explain visual discrimination in both firstand second-order patterns. However, the source and nonlinearity of the divisive inhibition may be different for these two types of patterns and carrier.

期刊Journal of Vision
出版狀態Published - 2014

All Science Journal Classification (ASJC) codes

  • 眼科
  • 感覺系統


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