A single-transient masking paradigm

Abstract

Visual masking, as typically studied in the twotransient paradigm (Matin, 1975), involves suppression of the visibility of one brief stimulus, the target, by another (spatio-jtemporally contiguous brief stimulus, the mask. Recent neurophysiologically based theories of visual masking rely on the existence, in the higher mammalian visual system, of short-latency, fast transient channels which inhibit longer latency, slower sustained channels (for review, see Breitmeyer & Ganz, 1976). In particular, recent theoretical approachesto visual masking, namely, thoseof Breitmeyer & Ganz (1976) and Weisstein, Ozog, and Szoc (1975), make use of this two-channel, transient-sustained distinction. Both approaches share the assumption that the typical Ll-shaped or type B metacontrast function (Kolers, 1962) is a consequence of the inhibition of the slow, target-activated sustained channels by the faster mask-activated transient channels in the target-mask sequence. The two models are similar in the specification of conditions required to activate the transient channels. For Breitmeyer and Ganz's (1976) and Weisstein et aI.'s (1975) model, it is sufficient that the mask activate fast transient channels, although both models acknowledge that either target or mask can and does activate both transient and sustained channels. The activation of transient channels by the target is not regarded as a necessary condition for obtaining metacontrast masking.However, Matin (1975)proposed a model in which activationof spatiotemporalsequence detectors, termed target-mask, or T-M, neurons, are required to produce type B metacontrast functions. In other words, Matin suggests that transient neurons may be a substrate for the T-M sequence detectors and that, in addition to the activation of mask transient neurons (Breitmeyer & Ganz, 1976;Weisstein et al., 1975), activation of target transient neurons is also necessary for producing metacontrast. The present experiment demonstrates that Matin (1975) may have been misled in her theorizing by the prevailing methodological rather than physiological facts.M. E, Rudd's present address:

Perceptual Alternation Induced by Visual Transients

“…These characteristics are shared by another transient-induced phenomenon, where a transient stimulus triggers fading of an object presented in the periphery (Kanai and Kamitani 2003;Moradi and Shimojo 2004; see also Breitmeyer and Rudd 1981;Wilke et al 2003). The fading effect shows the time-locked characteristics.…”

“…Third, adaptation to the dominant perceptual interpretation is necessary, and the strength of the effect depends on the depth of adaptation. Breitmeyer & Rudd, 1981). The fading effect shows the time-locked characteristics.…”

Disappearance elicited by contrast decrements

“…Since both the Troxler effect (Clarcke, 1957(Clarcke, , 1961 and visual masking (Breitmeyer & Rudd, 1981) increase with eccentricity, we examined the effect of this variable with CD in Experiment 4.…”

“…Traditionally, this phenomenon has been investigated by the presentation of targets and masking stimuli for brief periods while relative time (interstimulus interval [ISI] or stimulus onset asynchrony [SOA] ) and order of presentation (e.g., paracontrast or metacontrast) are varied. However, one study (Breitmeyer & Rudd, 1981) also demonstrated that a continuously viewed stimulus can be abruptly removed from conscious awareness by the brief presentation of nearby masking stimuli. This implies that disappearance need not involve local adaptation.…”

Dynamics of visual masking revealed by second-order metacontrast

“…Critically, all subjects in all three experiments had obvious type A metacontrast functions.2 Clearly, our "single transient stimuli" are very different from those ofBreitmeyer and Rudd (1981), where masking effects on a very long duration target are demonstrated. Although not identical, they bear some similarity to those ofBellefeuille and Faubert (1998), in which a certain proportion of pixels reversed polarity from frame to frame.3 After completion of the four randomized conditions of Experiment 1, participants first ran one session of Experiment 3, then Experiment 2 (one session), then another session of Experiment 3, all within a week.…”