Interocular Grouping in Perceptual Rivalry Localized with fMRI.

Area of Science:

• Neuroscience
• Cognitive Science
• Visual Perception

Background:

• Bistable perception and visual illusions like binocular rivalry offer insights into visual input integration.
• Previous fMRI studies identified cortical networks involved in binocular rivalry using replay control conditions.
• Interocular grouping, where elements from different eyes are perceptually linked, is a less understood aspect of rivalry.

Purpose of the Study:

• To investigate the neural correlates of interocular grouping during binocular and stimulus rivalry.
• To identify novel cortical areas activated by interocular grouping compared to rivalry without grouping.
• To compare the neural networks involved in interocular grouping with those previously identified for rivalry.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to study brain activity.
• Participants viewed ambiguous images inducing binocular rivalry, with and without interocular grouping.
• Stimulus rivalry (eye-swap) was used as a control, with similar analyses performed.

Main Results:

• Interocular grouping led to increased activation in cortical areas, with a right hemisphere lateralization shift.
• Direct comparison revealed focused activity in the intraparietal sulcus and lateral occipital areas (LO1, IP2, IP0-IP2) during grouping.
• Stimulus rivalry yielded similar results, with greater right superior parietal cortex recruitment for binocular rivalry.

Conclusions:

• Spatial integration, facilitated by interocular grouping, involves distinct but overlapping networks with rivalry mechanisms.
• The lateral occipital/intraparietal cortex plays a crucial role in spatial integration of competing binocular representations.
• These findings suggest that image grouping mechanisms operate similarly on competing visual stimuli regardless of the rivalry type.