Figure 3.

Selection of participants for the BOLD analysis as a function of PAS. The subjects were ranked according to the Akaike information criterion (AIC), obtained by maximum likelihood estimation of the fit of the individual Contrast-to-PAS linear function (blue dashed line) to a Contrast-to-PAS linear model function (gray line). The subsample was defined by selecting the best-ranked subjects, until AIC discontinuity from the n-ranked to the n+1-ranked subject (horizontal line in bottom inset). Subjects 14, 15, and 23 were excluded from the subsample because they presented higher than half-maximum (horizontal dashed line) PAS scores at contrast level Thrm1, indicating that a relatively high proportion of stimuli below perceptual threshold were actually visible to these subjects. This left the subsample with 12 subjects. This subsample of subjects presented a comparable modulation of behavioral subjective awareness by image contrast as the whole group (Fig. 4A), as well as comparable activation as a function of contrast both above and below perceptual threshold.