Search

Preceding contexts strongly influence current decision-making. To elucidate the neural mechanism that underlies this phenomenon, magnetoencephalographic signals were recorded while participants performed a binary categorization task on a sequence of facial expressions. The behavioral data indicated that the categorization of current facial expressions differed between the contexts shaped by the immediately preceding expression. We found that the effects of the preceding context were linked to prestimulus power activities in the low-frequency band. However, these context-dependent neural markers did not reflect behavioral decisions. Rather, the beta power observed primarily after stimulus onset and located at distinct sensors was predictive of the trial-by-trial decisions. Despite these results, the coupling strength between context-dependent and decision-related power differed between preceding contexts, suggesting that the context-dependent power interacted with decision-related power in a systemic manner and in turn biased behavioral decisions. Taken together, these findings suggest that categorization decisions are mediated by a series of power activities that coordinate the influence of preceding contexts on current categorization.

Although the nature of the relationship between attention and awareness is actively debated, the possibility that different forms of attention might interact differently with awareness has never been directly tested. We examine here whether voluntary and involuntary spatial attentions, two forms of attention that were distinguished by manipulating the predictability of central arrow cues, interact in the same way with visual awareness. Conscious perception was enhanced by both voluntary and involuntary attentions, and to a similar extent, suggesting volition may not be an essential feature for awareness. However, the influence of attention was dependent on the awareness of the target stimulus: Voluntary attention shortened reaction times and improved discrimination accuracy of cued relative to uncued stimuli, but only when the stimuli were consciously perceived. Involuntary attention shortened reaction times for cued relative to uncued target stimuli, but only when the stimuli were not consciously perceived. Our results imply that the nature of the relationship between attention and awareness is not a simple one but depends on the type of attention involved. More specifically, our results suggest that the aware or unaware status of the stimulus could determine whether attentional facilitation is driven by voluntary or involuntary mechanisms, a proposal that goes in the opposite direction of the classical view that attention controls awareness. Because voluntary attentional benefits were observed in aware trials but involuntary attentional benefits were observed in unaware trials only, our results also argue against the idea that attentional effects on conscious and unconscious processing are fundamentally of the same nature.