Central factors contributing to para-contrast modulation of contour and brightness perception

Abstract

Following up on a prior study of contour and brightness processing in visual masking (Breitmeyer et al., 2006), we investigated the effects of a binocular and dichoptic para-contrast masking on the visibility of the contour and brightness of a target presented to the other eye. Combined, the results support the contributions of several cortical processes to para-contrast: (1) two central sources of inhibition, one long-latency and prolonged and the other short-latency and brief; (2) binocular rivalry suppression; and (3) a facilitatory effect peaking at different SOAs for the contour and the brightness tasks, reflecting; (4) known properties of two separate cortical systems, one a fast contour-processing pathway and the other a slower brightness-processing pathway.

Combining simultaneous with temporal masking.

“…Also for the forward masking situation (SOAs< 0), we found the strongest masking at a non-zero SOAs. Although such Btype masking is regularly found in backward masking, it is much less frequently observed in forward masking (exceptions include Breitmeyer, Ziegler, & Hauske, 2007;Green, Nuechterlein, Breitmeyer, & Mintz, 2006;Ögmen, Breitmeyer, & Melvin, 2003). Two of the studies that found Type-B forward masking showed strongest masking at a value comparable to ours (Breitmeyer et al, 2007;Green et al, 2006) In the following experiments, we demonstrate that the simultaneous and temporal masks have separate effects on the target, but that the masking effects of both types of masks depends on their mutual interactions.…”

Interferences of visual masks with semantic and perceptual priming effects

“…Considering priming effects as measures of stimulus processing creates new avenues to investigate the effects of masking on stimulus processing, especially since priming effects are a hitherto rarely used measure to determine the effects of masks. In line with findings of visibility reductions by forward masks (Breitmeyer et al, , 2007Macknik & Martinez-Conde, 2007), it has been shown that the suppression effect depends on the duration and temporal delay of forward masks. On the other hand, our results reveal different effects of forward masks on priming effects and visibility.…”

“…The suppression effect wears off at larger ISIs, especially for short forward masks. However, forward masks are still efficient in masking stimuli at intermediate ISIs (Macknik & Martinez-Conde, 2007) and long ISIs (see Experiment 4.4) even with very brief forward masks (Breitmeyer et al, 2007). If forward masks reduce stimulus visibility in a time window when the suppression effect is not active anymore, forward masks may thus still be a viable tool to decrease visibility without compromising priming effects.…”

“…The stimulus energy is, amongst others, determined by the luminance and duration of the stimuli (Breitmeyer & Öǧmen, 2006, p. 48;Duangudom, Francis, & Herzog, 2007). The effects of paracontrast masking are often smaller than that of metacontrasts, but can last for a long time span between forward mask and the masked stimulus Öǧmen, Breitmeyer, & Melvin, 2003), even when presented dichoptically (Breitmeyer, Ziegler, & Hauske, 2007). The data of demonstrate that the obtained masking functions depend on the visibility task: While paracontrast masking exhibited a type-A-like function with maximal masking at an inter-stimulus-interval (ISI) of zero milliseconds in a contour discrimination task, the perceived brightness of the target varied according to a complex function and was even increased at ISIs around 50 ms.…”

“…Such simple shapes allow for a good alignment of target and mask contours. Paracontrast and metacontrast masking are not limited to monoptic stimulus presentations but can also be obtained in a dichoptic paradigm where target and masks are presented to different eyes (Breitmeyer & Ganz, 1976;Breitmeyer et al, 2007;Schiller & Smith, 1968), including with colored stimuli (Yellott & Wandell, 1976).…”