Abstract
The functional role of subcortical structures in binocular rivalry remains poorly understood. The superior colliculus (SC) is one of the key structures in subcortical visual pathways. To address the question whether the SC participates in binocular rivalry, we used high-resolution functional magnetic resonance imaging to measure the activity of the SC during binocular rivalry. Two orthogonal gratings with different colors (red/green) and contrasts (100% / 15%) were dichoptically presented. While in the scanner, subjects viewed the stimulus through anaglyphic glasses and tracked the relative dominance of these two gratings by pressing one of two buttons. The BOLD signal level of the SC correlated well with subjects' perception, increasing when the high contrast grating became dominant and decreasing when the low contrast one was perceived. This BOLD signal modulation was similar to that observed in the replay condition, during which the two monocular stimuli were physically alternating between the two eyes. BOLD signals consistent with perceptual rivalry alternations were found in the LGN and V1. The subcortical pathway through the SC is considered an alternative pathway to the geniculate-striate pathway, and is often considered to be a pathway supporting unconscious visual information processing. However, our results suggest that binocular rivalry also occurs in the SC, which has significant implications on our understanding of the neural mechanisms supporting unconscious visual information processing.
Research supported by grants EY015261 and NSF/BCS-0818588.