title: GABAA agonist reduces visual awareness: a masking-EEG experiment.
abstract: Consciousness can be manipulated in many ways. Here, we seek to understand whether two such ways, visual masking and pharmacological intervention, share a common pathway in manipulating visual consciousness. We recorded EEG from human participants who performed a backward-masking task in which they had to detect a masked figure form its background (masking strength was varied across trials). In a within-subject design, participants received dextromethorphan (a N-methyl-d-aspartate receptor antagonist), lorazepam (LZP; a GABA(A) receptor agonist), scopolamine (a muscarine receptor antagonist), or placebo. The behavioral results show that detection rate decreased with increasing masking strength and that of all the drugs, only LZP induced a further decrease in detection rate. Figure-related ERP signals showed three neural events of interest: (1) an early posterior occipital and temporal generator (94-121 msec) that was not influenced by any pharmacological manipulation nor by masking, (2) a later bilateral perioccipital generator (156-211 msec) that was reduced by masking as well as LZP (but not by any other drugs), and (3) a late bilateral occipital temporal generator (293-387 msec) that was mainly affected by masking. Crucially, only the intermediate neural event correlated with detection performance. In combination with previous findings, these results suggest that LZP and masking both reduce visual awareness by means of modulating late activity in the visual cortex but leave early activation intact. These findings provide the first evidence for a common mechanism for these two distinct ways of manipulating consciousness.
authors.affiliation: Department of Psychology, University of Amsterdam, Weesperplein 4, 1018 XA, Amsterdam, The Netherlands. anouk.vanloon@gmail.com
authors.forename: Anouk M
authors.initials: AM
authors.lastname: van Loon
authors.forename: H Steven
authors.initials: HS
authors.lastname: Scholte
authors.forename: Simon
authors.initials: S
authors.lastname: van Gaal
authors.forename: Björn J J
authors.initials: BJ
authors.lastname: van der Hoort
authors.forename: Victor A F
authors.initials: VA
authors.lastname: Lamme
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001364:Awareness / Q000187:drug effects*; D003915:Dextromethorphan / Q000494:pharmacology; D004569:Electroencephalography; D005074:Evoked Potentials, Visual / Q000187:drug effects*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D018755:GABA Agonists / Q000494:pharmacology*; D006801:Humans; D008140:Lorazepam / Q000494:pharmacology*; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009949:Orientation / Q000187:drug effects; D010470:Perceptual Masking / Q000502:physiology*; D010775:Photic Stimulation; D011930:Reaction Time / Q000187:drug effects; D012601:Scopolamine / Q000494:pharmacology; D013997:Time Factors; D014793:Visual Cortex / Q000187:drug effects / Q000502:physiology; D014796:Visual Perception / Q000187:drug effects*; D055815:Young Adult
chemical_list: D018691:Excitatory Amino Acid Antagonists; D018755:GABA Agonists; D018727:Muscarinic Antagonists; D003915:Dextromethorphan; D012601:Scopolamine; D008140:Lorazepam