Abstract
This study investigated how different types of eyeblinks, i.e., spontaneous (unintentional) and voluntary (intentional) eyeblinks, affect target detection during continuous flash suppression (CFS). CFS refers to a strong interocular suppression that can be produced by presenting a high-contrast dynamic pattern (suppressor) to one eye. In this study, we used breaking CFS paradigm in which after exclusive dominance of the suppressor had been established, luminance contrast of a target, which was presented to the other eye, was ramped up to its maximum (0.8) over 3.0 sec. The time required for target detection was measured. The suppressor was a color Mondrian pattern refreshed at 10 Hz, and the target was a Gabor patch (1.06 cpd, clockwise or counter-clockwise orientation, σ = 1°). Results showed that the detection time was longer when a spontaneous eyeblink occurred before target detection than when no blink occurred. However, time interval between an eyeblink and target detection was very variable, suggesting that spontaneous eyeblinks themselves did not affect target detection. By contrast, the detection time was shorter when a voluntary eyeblink was generated in response to a visual cue. Moreover, a close temporal relationship was found between a voluntary eyeblink and target detection; the detection time was peaked 0.5 sec after eyeblinks. Differential effects of spontaneous and voluntary eyeblinks on target detection suggested that a transient change in a retinal image caused by eyeblinks did not play a critical role in modulating target detection. Consistently, a physical blackout, which was produced by darkening the stimulus display and had timing and duration comparable to eyeblinks, did not affect target detection. Furthermore, we also found that the detection time was shorter when voluntary eyelid opening was generated. Collectively, the present findings suggested that extra-retinal processing associated with voluntary eyelid movements facilitates target detection during CFS.