  The goal of the present investigation was to identify reliable markers of
conscious visual perception and to characterize their onset latency and its
variability. To that end many visual stimuli from different categories were
presented at near-threshold contrast and contrastive analyses were carried out
on 100 balanced subsets of the data. N200 and P300 were the two reliable
markers of conscious perception common to all perceived stimuli and absent for
all nonperceived stimuli. The estimated mean onset latency for both markers was
shortly after 200 ms. However, the onset latency of both of these markers of
conscious perception showed considerable variability depending on which subsets
of the data were considered. Some of this variability could be attributed to
noise, but it was first and foremost the amplitude fluctuation in the condition
without conscious perception that explained the variability in onset latencies
of the markers of conscious perception. The present results help to understand
why different studies have observed different onset times for the neural
correlates of conscious perception. Moreover, the consciousness markers
explored here have more generality as stimulus specificity was reduced.
