title: Semantic processing in subliminal face stimuli: an EEG and tDCS study.
abstract: Whether visual subliminal processing involves semantic processing is still being debated. To examine this, we combined a passive electroencephalogram (EEG) study with an application of transcranial direct current stimulation (tDCS). In the masked-face priming paradigm, we presented a subliminal prime preceding the target stimulus. Participants were asked to determine whether the target face was a famous face, indicated by a button press. The prime and target pair were either the same person's face (congruent) or different person's faces (incongruent), and were always both famous or both non-famous faces. Experiments were performed over 2 days: 1 day for a real tDCS session and another for a sham session as a control condition. In the sham session, a priming effect, reflected in the difference in amplitude of the late positive component (250-500 ms to target onset), was observed only in the famous prime condition. According to a previous study, this effect might indicate a subliminal semantic process [10]. Alternatively, a priming effect toward famous primes disappeared after tDCS stimulation. Our results suggested that a subliminal process might not be limited to processes in the occipital and temporal areas, but may proceed to the semantic level processed in prefrontal cortex.
authors.affiliation: Department of Computer Science and Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka Tempaku, Toyohashi, Aichi 441-8580, Japan.
authors.forename: Nutchakan
authors.initials: N
authors.lastname: Kongthong
authors.forename: Tetsuto
authors.initials: T
authors.lastname: Minami
authors.forename: Shigeki
authors.initials: S
authors.lastname: Nakauchi
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D003463:Cues; D004569:Electroencephalography / Q000379:methods; D005145:Face; D005260:Female; D006801:Humans; D008297:Male; D010470:Perceptual Masking / Q000502:physiology*; D060865:Repetition Priming / Q000502:physiology*; D012660:Semantics; D013360:Subliminal Stimulation; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult