Frequency-tagging visual background information enables multi-target perceptual filling-in to be distinguished from phenomenally matched replay

• Published in: bioRxiv
• Main Authors: Davidson, Matthew James, Graafsma, Irene, Tsuchiya, Naotsugu, Van Boxtel, Jeroen Ja
• Format: Paper
• Language: English
• Published: Cold Spring Harbor Cold Spring Harbor Laboratory Press 18.12.2018
• Subjects: Consciousness; EEG; Visual perception
• DOI: 10.1101/499517

Perceptual filling-in (PFI) occurs when a physically-present visual target disappears from conscious perception, with its location filled-in by the surrounding visual background. Compared to other visual illusions, these perceptual changes are crisp and simple, and can occur for multiple spatially-separated targets simultaneously. Contrasting neural activity during the presence or absence of PFI may complement other multistable phenomena to reveal the neural correlates of consciousness (NCC). We presented four peripheral targets over a background dynamically flickering at 20 Hz, to entrain neural populations responding to the background. While participants reported on target disappearances/reappearances via button press/release, we tracked neural activity associated with PFI using steady-state visually evoked potentials (SSVEPs) recorded in the electroencephalogram. Behaviorally, we found that as the number of filled-in targets increased, the duration of target disappearances also increased, suggesting faciliatory interactions among targets located in separate visual quadrants. We found background SSVEPs closely correlated with subjective report, and increased with an increasing amount of PFI. Unexpectedly, we found distinct spatiotemporal correlates for the SSVEP harmonics. Prior to PFI, the response at 40 Hz preceded the response at 20 Hz, which we tentatively link to an attentional effect. There was no difference between harmonics for physically removed stimuli. These results demonstrate that PFI can be used to study multi-object faciliatory interactions, and because there are distinct neural correlates for endogenously and exogenously induced changes in consciousness, it is ideally suited to study the NCC.