Unconscious attention modulates the silencing effect of top-down predictions.

The brain is considered to be proactive in that it continuously generates predictions about external environment stimuli. Recent Bayesian models of perception have demonstrated that prediction and attention operate synergistically to optimize stimulus processing. However, the relation between prediction and unconscious attention remains unclear given the relative neglect of unconscious attention in scholarly literatures. To investigate this issue, twenty participants (12 women) performed an orientation identification task in which a circular grating appeared either in the left or in the right visual field in a single 30-40min session, during which 64-channel EEG data were acquired. Behavioral results showed an unconscious-attended effect and a facilitated effect. Importantly, prediction-related P1 and N1 silencing effects were observed in the unconscious-attended condition, probably reflecting that unconscious attention improves the precision of top-down predictions at an early stage of processing, thereby increasing the synaptic gain of predictor neurons. Moreover, unlike the early ERP components, P3 revealed a reversed pattern of results, which displayed a silencing effect of prediction only in the unattended condition, suggesting that the influence of unconscious attention on the silencing effect may change over time.