The earliest electrophysiological correlate of visual awareness?
To examine the neural correlates and timing of human visual awareness, we recorded event-related potentials (ERPs) in two experiments while the observers were detecting a grey dot that was presented near subjective threshold. ERPs were averaged for conscious detections of the stimulus (hits) and nondetections (misses) separately. Our results revealed that hits, as compared to misses, showed a negativity around 180-350 ms at occipital and posterior temporal sites. It was followed by a positive wave after 400-500 ms, peaking at parietal sites. These correlates were not affected by a manipulation of attention. The early negativity, called 'visual awareness negativity' (VAN), may be a general, primary electrophysiological correlate of visual awareness. The present data show that it can be observed in response to appearance of a stimulus in visual awareness and that it generalizes across different manipulations of stimulus visibility.
Centre for Cognitive Neuroscience, University of Turku, 20014 Turku, Finland. mika.koivisto@utu.fi
Mika
M
Koivisto
Mikko
M
Lähteenmäki
Thomas Alrik
TA
Sørensen
Signe
S
Vangkilde
Morten
M
Overgaard
Antti
A
Revonsuo
D000328:Adult; D000704:Analysis of Variance; D001364:Awareness / Q000502:physiology*; D003265:Contingent Negative Variation / Q000502:physiology; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D012684:Sensory Thresholds / Q000502:physiology*; D013702:Temporal Lobe / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*