A central red fixation cross 0.63° in diameter was continuously present on the screen. Mean luminance of the background pattern was 10.76 cd/m 2. For all phases of the experiment, the background consisted of a spatially modulated, random white noise pattern. Head position was stabilized using a chin rest. Cathode ray tube (CRT) monitor (Samsung Syncmaster, Suwong, Korea) with 1280 × 1024 pixel resolution and a refresh rate of 100 Hz, located 56 cm from the participants' eyes. Stimuli were presented on a gamma-linearized 19-in. Participants were seated in a dark, sound-attenuated chamber. The experiment was programmed in Matlab (Mathworks, Inc., Natick, MA) using the Psychophysics Toolbox (Brainard, 1997). In line with previous reports, we propose that the function underlying this effect is the inhibition of spurious noise by the visual system. This finding indicates that subliminal, low-intensity stimuli induce a similar inhibitory effect in the visual system as has been observed in the somatosensory system. We demonstrate that target detection was impaired by the subliminal stimuli, but only when they were presented at the same location as the target.
Subliminal stimuli were invisible due to their low contrast, not due to a masking procedure. We tested the detection of peripheral visual target stimuli under three different conditions: Target stimuli were presented alone or embedded in a concurrent train of subliminal stimuli either at the same location as the target or in the opposite hemifield. In the current study, we investigated whether a behavioral inhibitory mechanism also exists within the visual system. In a recent study, we showed that subliminal visual stimuli lead to similar responses, indicated by an increase in alpha-band power as measured with electroencephalography (EEG). Abstract What is the perceptual fate of invisible stimuli-are they processed at all and does their processing have consequences for the perception of other stimuli? As has been shown previously in the somatosensory system, even stimuli that are too weak to be consciously detected can influence our perception: Subliminal stimulation impairs perception of near-threshold stimuli and causes a functional deactivation in the somatosensory cortex.