Visual awareness of low-contrast stimuli is reflected in event-related brain potentials

Authors


Address reprint requests to: Ville Ojanen, Laboratory of Computational Engineering, Helsinki University of Technology, P.O. Box 9400, FIN-02015 HUT, Finland. E-mail: viloja@lce.hut.fi.

Abstract

Visual awareness was studied in 11 subjects by using coherent and scrambled objects as stimuli. The stimuli were presented near the subjective perceptual threshold. Explicitly recognized stimuli elicited a specific negative ERP deflection peaking at 460 ms. Our reaction time experiment suggests that this visual awareness negativity (VAN) is similar to that found previously at a shorter latency. We propose that VAN might reflect the exact moment of becoming aware of the task-relevant stimulus properties and provide an online marker of the temporal dynamics of visual awareness.

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