title: Invisible visual stimuli elicit increases in alpha-band power.
abstract: The cerebral cortex responds to stimuli of a wide range of intensities. Previous studies have demonstrated that undetectably weak somatosensory stimuli cause a functional deactivation or inhibition in somatosensory cortex. In the present study, we tested whether invisible visual stimuli lead to similar responses, indicated by an increase in EEG alpha-band power-an index of cortical excitability. We presented subliminal and supraliminal visual stimuli after estimating each participant's detection threshold. Stimuli consisted of peripherally presented small circular patches that differed in their contrast to a background consisting of a random white noise pattern. We demonstrate that subliminal and supraliminal stimuli each elicit specific neuronal response patterns. Supraliminal stimuli evoked an early, strongly phase-locked lower-frequency response representing the evoked potential and induced a decrease in alpha-band power from 400 ms on. By contrast, subliminal visual stimuli induced an increase of non-phase-locked power around 300 ms that was maximal within the alpha-band. This response might be due to an inhibitory mechanism, which reduces spurious visual activation that is unlikely to result from external stimuli.
authors.affiliation: Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; The MindBrain Institute, Humboldt-Universität zu Berlin, Berlin, Germany; isabelle.bareither@gmail.com.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Bareither
authors.affiliation: Berlin School of Mind and Brain, Humboldt-Universität zu Berlin, Berlin, Germany; and.
authors.forename: Maximilien
authors.initials: M
authors.lastname: Chaumon
authors.affiliation: Institute of Medical Psychology, Charité University Medicine, Berlin, Germany.
authors.forename: Fosco
authors.initials: F
authors.lastname: Bernasconi
authors.affiliation: Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; The MindBrain Institute, Humboldt-Universität zu Berlin, Berlin, Germany;
authors.forename: Arno
authors.initials: A
authors.lastname: Villringer
authors.affiliation: Berlin School of Mind and Brain, Humboldt-Universität zu Berlin, Berlin, Germany; and Institute of Medical Psychology, Charité University Medicine, Berlin, Germany.
authors.forename: Niko A
authors.initials: NA
authors.lastname: Busch
mesh_terms: D000293:Adolescent; D000328:Adult; D000513:Alpha Rhythm; D002540:Cerebral Cortex / Q000502:physiology*; D005074:Evoked Potentials, Visual; D005260:Female; D006801:Humans; D008297:Male; D013360:Subliminal Stimulation; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: EEG; alpha-band; event-related synchronization; oscillations; subthreshold stimulation