Abstract
Continuous flash suppression (CFS), a potent form of binocular rivalry introduced by Tsuchiya and Koch (2005), has become a popular tool for rendering stimuli perceptually invisible. But why is CFS so effective at producing interocular suppression? We sought to identify visual properties that empower CFS and, thereby, to infer something about the neural representation of the stimulus being suppressed. In Experiment 1 we measured contrast thresholds for detecting a gabor patch (embedded in 1D, broadband noise) that was dichoptically paired either with a CFS display (dynamic 10Hz noise patterns) or with a gray screen. Compared to contrast thresholds measured without CFS, thresholds under CFS were strongly elevated when the gabor was low spatial frequency (0.5-4cpd) but less so when it was high spatial frequency (8-16cpd). In Experiment 2, we manipulated spatial frequency content of the CFS and found that a low-pass filtered CFS (0.5-4cpd) produced elevated thresholds similar to those measured when the CFS was unfiltered. High-pass filtered CFS (8-16cpd), however, produced no elevation in thresholds. In Experiment 3 we varied the temporal frequency of unfiltered CFS displays. 5Hz CFS elevated thresholds only for a low spatial frequency gabor (1cpd), whereas 20 Hz CFS produced the same pattern of threshold elevations as did 10 Hz CFS. We conclude that transients produced by rapid, abrupt flicker, together with random changes in pattern shape and contrast over time, create a suppressor that is itself immune to adaptation and that selectively impairs low-spatial frequency components of stimuli presented to the opposing eye. This selectivity of suppression underscores the importance of considering spatial frequency content of stimuli suppressed by CFS. Indeed, the present results may shed new light on the selective effects of CFS on different object categories (e.g. tools vs faces) reported in behavioral and neuroimaging studies. We are currently examining this possibility.
NIH EY13358 & 5T32 EY007135.