title: Neuronavigated transcranial magnetic stimulation suggests that area V2 is necessary for visual awareness.
abstract: The primary visual cortex (V1) has been shown to be critical for visual awareness, but the importance of other low-level visual areas has remained unclear. To clarify the role of human cortical area V2 in visual awareness, we applied transcranial magnetic stimulation (TMS) over V2 while participants were carrying out a visual discrimination task and rating their subjective awareness. Individual retinotopic maps and modelling of the TMS-induced electric field in V1, V2 and V3d ensured that the electric field was at or under the phosphene threshold level in V1 and V3d, whereas in V2 it was at the higher suppressive level. As earlier shown for the V1, our results imply that also V2 is necessary for conscious visual experience. Visual awareness of stimulus presence was completely suppressed when the TMS pulse was delivered 44-84 ms after the onset of visual stimulus. Visual discrimination and awareness of stimulus features was impaired when the TMS pulse was delivered 44-104 ms after the visual stimulus onset. These results suggest that visual awareness cannot be generated without an intact V2.
authors.affiliation: Centre for Cognitive Neuroscience, University of Turku, FIN-20014 Turku, Finland. niisalm@utu.fi
authors.forename: Niina
authors.initials: N
authors.lastname: Salminen-Vaparanta
authors.forename: Mika
authors.initials: M
authors.lastname: Koivisto
authors.forename: Valdas
authors.initials: V
authors.lastname: Noreika
authors.forename: Simo
authors.initials: S
authors.lastname: Vanni
authors.forename: Antti
authors.initials: A
authors.lastname: Revonsuo
mesh_terms: D000328:Adult; D001364:Awareness; D001703:Biophysics; D001931:Brain Mapping; D004192:Discrimination, Psychological / Q000502:physiology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood; D010775:Photic Stimulation / Q000379:methods; D050781:Transcranial Magnetic Stimulation; D014793:Visual Cortex / Q000098:blood supply* / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
chemical_list: D010100:Oxygen