The "serendipitous brain". Low expectancy and timing uncertainty of conscious events improve awareness of unconscious ones (evidence from the Attentional Blink)

To anticipate upcoming sensory events, the brain picks-up and exploits statistical regu- larities in the sensory environment. However, it is untested whether cumulated predictive knowledge about consciously seen stimuli improves the access to awareness of stimuli that usually go unseen. To explore this issue, we exploited the Attentional Blink (AB) effect, where conscious processing of a first visual target (T1) hinders detection of early following targets (T2). We report that timing uncertainty and low expectancy about the occurrence of consciously seen T2s presented outside the AB period, improve detection of early and otherwise often unseen T2s presented inside the AB. Recording of high-resolution Event Related Potentials (ERPs) and the study of their intracranial sources showed that the brain achieves this improvement by initially amplifying and extending the pre-conscious storage of T2s' traces signalled by the N2 wave originating in the extra-striate cortex. This enhancement in the N2 wave is followed by specific changes in the latency and amplitude of later components in the P3 wave (P3a and P3b), signalling access of the sensory trace to the network of parietal and frontal areas modulating conscious processing. These findings show that the interaction between conscious and unconscious processing changes adap- tively as a function of the probabilistic properties of the sensory environment and that the combination of an active attentional state with loose probabilistic and temporal expec- tancies on forthcoming conscious events favors the emergence to awareness of otherwise unnoticed visual events. This likely provides an insight on the attentional conditions that predispose an active observer to unexpected “serendipitous” findings