driven network should become disorganized (because it is being driven by noise), and the chromatic networkshould desynchronize from it. Segmentation mistakes inthe unreinforced chromatic network should now occur. Combining Equiluminance and Stabilization— Effects and Predictions Many of the binding failures discussed above seem connected. Equiluminant border melting has obvioussimilarities to border fading in image stabilization. Sim-ilarly, the ''jazziness'' of equiluminant borders may be afast time-scale analog to the fragmentation and dis/reappearance of some stabilized images. The comple-tion of gaps in reappearances of stabilized imagesresembles filling-in phenomena seen for some equilumi-nous images. In general, nulling the signal to a reinforc-ing channel should be detrimental to the channel itreinforced: The reinforcement is lost and lost informa-tion is replaced with mere noise. Significantly, for sub-jects who have one of the color, motion, and achromaticform systems disrupted, interrupting another systemresults in a more dramatic effect. For example, Sacksand Wasserman (1987) find that for an achromatopsic observer, boundaries between areas dissolved during periods of steady fixation (see below for analogousfindings in color normals). Similarly, stimuli that stimu-late only the b-y pathway (tritanopic stimuli) are partic-ularly susceptible to dissolution of contours (Cavanagh,1991). If the visual system requires two cooperatingsystems to achieve segmentation, then we would predictthat combining equiluminance and stabilization should be especially devastating. In fact, steadily fixated colored stimuli do fade more readily when equiluminant to theirsurroundings (Livingstone & Hubel, 1987; Buck et al.,1977; Krauskopf, 1967). Still more dramatic effects areobtained by combining retinal stabilization and equilu-minance. Billock et al. (2001) and Crane and Piantanida(1983) report that if a stabilized red/green or blue/yellowbipartite field is viewed through an unstabilized aper-ture, the colors flow and mix across the faded border. Some observers perceive uniform reddish greens oryellowish blues, in violation of color opponency. Otherobservers report formation of fine color textures orunstable islands of one color continuously forming anddissolving in a sea of the other color. Billock et al. foundthis spurious segmentation occurs only when there is aluminance difference between the two stabilized colored fields. Moreover, while melting together of adjacent equiluminant fields is normally seen only for tritanopicpairs, Billock et al. found that the phenomenon occursfor any stabilized color pair. (Related and extreme casesof binding failures are found in some neurologicaldisorders; Friedman-Hill, Robertson, & Treisman, 1995;Sacks, 1995; Zeki, 1993; Critchley, 1965). Given our reasoning and these preliminary results, a test of our reinforcement hypothesis would be tomeasure both perceptual segmentation and electro-physiological measures of binding while equiluminanceand stabilization are manipulated. The psychophysics isstraightforward. For experiments on equiluminance, animage is made of at least two colors, and radianceratios of the colors are varied through the range inwhich the equiluminance ratio must lie. Whether lossof neural binding signatures occurred at equiluminance can be determined by measuring figure and back-ground luminosities using standard psychophysicaltechniques (Cavanagh, 1991; Wyszecki & Stiles, 1982). Specific information should be gathered with respect toperceptual state (e. g., border instability, border melting,surface delinking). Similarly, image stabilization isstraightforward, albeit technically challenging and ex-pensive (Crane, 1994); useful results can often be had with afterimages or steady fixation (Ditchburn, 1973). Electrophysiological states should be correlated withthe specific perceptual state elicited (e. g., fragmenta-tion, fading, etc. ). If a stabilization system is available,t h ed e g r e eo fs t a b i l i z a t i o nc a nb em a n i p u l a t e db ymoving the image independently of eye movementsor by manipulating the gain of the eye-movement $ image-movement feedback loop (Crane, 1994). Finding what neural signatures to use (and how to test for them noninvasively in responding humans) is more challeng-ing. Since g-band activity is implicated in binding, the loss of higher-frequency EEG power during perceptuallosses in image stabilization is suggestive (Keesey &Nichols, 1967; Lehmann et al., 1965). There are twolimitations with this approach: Some sources of g-band power may be unrelated to binding and some binding failures may represent incorrect bindings and therefore not be identifiable by EEG. Recent experiments offerhelp on both counts, by studying gestalt perception(pop-out) of fragmented images hidden in camouflage. This fragmentation-to-order shift is complementary tothe order-to-fragmentation effects we wish to study. Subjects had g-band activity whether they saw a coher-ent image pop-out or not, but for coherent percepts the outputs of widely spaced electrodes became more correlated (as would be expected for synchronization;Gruber et al., 2002) and a different kind of g-band activity ''the induced gamma response'' was recorded. On every physically identical trial, there was a g-band response phase-locked to the stimulus, but only ontrials where the gestalt percept was obtained was thereanother EEG signature, consisting of g-band bursts in variable phase to the stimulus (Gruber et al., 2002; Tallon-Baudry & Bertrand, 1999; Tallon-Baudry, Ber-trand, Delpuech, & Pernier, 1996). We therefore predictthat EEG signatures like ''induced gamma'' will bereduced during binding failures induced by retinalstabilization (especially fragmentation) and equilumi-nance (e. g., loss of Gestalt symmetry in Glass patterns;Cavanagh, 1991). Moreover, we posit that these signa-tures should be further reduced by combining equilumi-Billock and Tsou 1045