Relationships among visual awareness, reaction time, and lateralized readiness potential in a simple reaction time task under the backward masking paradigm.

The goal of the present study was to examine whether a backward masking paradigm, in which a prime and a mask stimuli were consecutively presented with a short stimulus onset asynchrony, affected the time needed for either the perceptual or motor stages of processing and the simple reaction times. The times needed for the perceptual and motor stages were evaluated by measuring the stimulus-locked and response-locked lateralized readiness potentials. The results showed that the onset of the stimulus-locked lateralized readiness potentials under the backward masking paradigm took place earlier than it did under the condition of a mask stimulus presented alone, whereas the onset of the response-locked lateralized readiness potentials did not significantly differ under different stimulus conditions. These results suggested that the participants responded to the masked prime stimulus despite being unaware of the prime stimulus. This may have been mediated by facilitation of the perceptual rather than motor stages.