Pattern Masking

Pattern Masking

Our knowledge of spatial processing has benefited from the numerous studies carried out on pattern masking paradigm. Typically, pattern masking is studied by evaluating the detectability of a target in the presence of masks of different contrasts (TvC function). By measuring TvC function, one can derive the contrast response function of the target detectors with a simple mathematical transform. The “contrast” response function indicates the existence of the feature representation for contrast. It is well-known that the contrast response function of a neuron in the visual cortex is like sigmoid function: the response rate increases as the contrast increases and saturates at higher contrast. However, the visual system’s contrast response function cannot be measured directly and is needed to derive from the TvC function. If the target and mask share the same mechanism, the discrimination threshold starts to decrease with the increase of the pedestal contrast then decrease with the pedestal contrast linearly on the log-log unit. It is also called dipper function. The relationship between contrast response function and TvC function is explained below: suppose that a certain unit response is required by the system to detect a target. If the mask’s contrast is low, the response function is on its accelerating part and less contrast of the target is needed to reach unit response. However, if the mask contrast is high, the response function is in its decelerating part and more contrast of the target is needed to reach unit response (see Figure 1).

The dipper function is commonly explained as the consequence of a contrast transducer (Foley & Legge, 1981; Legge & Foley, 1980) , contrast gain control (Foley, 1994; Foley & Chen, 1999) or stimulus uncertainty (Klein & Levi, 2009; Pelli, 1985) . Although these explanations have been successful in describing the results for narrow-band stimuli, they fail when broadband stimuli are involved in pattern masking.

One of the important research lines is to develop a contarst-gain control model to explain TvC functions with broadband stimuli under monocular, binocular and dichoptic viewing configuration.

• Huang, P.C., Maehara, G., May, K. A. & Hess, R. F. (2012). Pattern masking: the importance of remote spatial frequencies and their phase alignment. [Abstract] J Vis, 12(2):14, 1-13. [full text]

• Maehara, G., Huang, P.C., & Hess, R. F. (2010). The effects of flankers on contrast detection and discrimination in binocular, monocular, and dichoptic presentation. [Abstract] J Vis, 10(4): 13, 1–15. [full text]

• Huang, P. C., & Chen, C.-C. (2009). "Pattern masking investigations of the 2nd-order visual mechanisms." Proc. SPIE, Vol. 7240, 724016.