Yih-Shiuan Lin¹ (), Serena Castellotti^2,3, Maria Del Viva³, Chien-Chung Chen^4,5, Mark Greenlee¹; ¹Institute of Psychology, University of Regensburg, ²Department of Translational Research on New Technologies in Medicine and Surgery, University of Pisa, ³Department of Neurosciences, Psychology, Drug Research and Child Health (NEUROFARBA), University of Florence, ⁴Department of Psychology, National Taiwan University, ⁵Neurobiology and Cognitive Science Center, National Taiwan University

Perceptual filling-in describes how the visual system compensates for missing information by interpolating from surrounding features. Two examples are artificial scotoma (AS) filling-in, perceived within blank regions embedded in dynamic noise after prolonged fixation, and contour erasure (CE), where brief adaptation to a flickering outline renders an object instantaneously invisible. Our study examines the interaction between AS and CE filling-in effects to reveal the underlying mechanisms. AS was induced using a high-contrast (-1dB) dynamic noise background (10 Hz) with two 7°-eccentric blank disks (3° diameter) in the left and right upper quadrants. With steady fixation, AS filling-in could be induced within these blank regions. CE was induced by counterphase flickering high-contrast (-1dB) contours (6 Hz) that outlined these blank regions. After 8 seconds of adaptation to mean luminance, CE, AS, or both, two stimuli (random noise disks, duration 100ms) were shown at the filling-in locations: participants had to discriminate the target, superimposed randomly on either side of the pedestal locations. Pedestal contrasts ranged from -∞ to -10 dB. Target thresholds showed a dipper shape, decreasing at low pedestal contrasts and increasing at high contrasts. Both AS and CE adaptation increased target thresholds when presented alone. However, superimposing CE on AS resulted in minimal threshold increase, and participants reported less AS filling-in, when CE was present. When CE preceded AS adaptation by 2 seconds, the percentage of subjective filling-in reports increased (from 58% to 73%), and the time to perceived filling-in was reduced (from 6.09s to 5.11s). These findings suggest that CE can facilitate AS filling-in when presented sequentially, but not simultaneously. Our results can be explained by a divisive inhibition model in which an inhibitory sensitivity parameter and a normalizing constant capture the adaptation effects. Our findings highlight the interplay between these two filling-in effects.

Acknowledgements: This study is supported by the Deutsche Forschungsgemeinschaft (DFG, GR 988/27-1) and the National Science and Technology Council (NSTC, 110-2923-H-002-004-MY3).