Microsaccades counteract perceptual filling-in

• Published in: Journal of vision (Charlottesville, Va.) Va.), 2008-11, Vol.8 (14), p.15.1-15
• Main Authors: Troncoso, Xoana G, Macknik, Stephen L, Martinez-Conde, Susana
• Format: Article
• Language: English
• Subjects: Adaptation, Physiological; Female; Fixation, Ocular; Humans; Male; Saccades; Scotoma - physiopathology; Vision, Ocular
• ISSN: 1534-7362; 1534-7362
• DOI: 10.1167/8.14.15

Artificial scotomas positioned within peripheral dynamic noise fade perceptually during visual fixation (that is, the surrounding dynamic noise appears to fill-in the scotoma). Because the scotomas' edges are continuously refreshed by the dynamic noise background, this filling-in effect cannot be explained by low-level adaptation mechanisms (such as those that may underlie classical Troxler fading). We recently showed that microsaccades counteract Troxler fading and drive first-order visibility during fixation (S. Martinez-Conde, S. L. Macknik, X. G. Troncoso, & T. A. Dyar, 2006). Here we set out to determine whether microsaccades may counteract the perceptual filling-in of artificial scotomas and thus drive second-order visibility. If so, microsaccades may not only counteract low-level adaptation but also play a role in higher perceptual processes. We asked subjects to indicate, via button press/release, whether an artificial scotoma presented on a dynamic noise background was visible or invisible at any given time. The subjects' eye movements were simultaneously measured with a high precision video system. We found that increases in microsaccade production counteracted the perception of filling-in, driving the visibility of the artificial scotoma. Conversely, decreased microsaccades allowed perceptual filling-in to take place. Our results show that microsaccades do not solely overcome low-level adaptation mechanisms but they also contribute to maintaining second-order visibility during fixation.