Characterizing Human Disparity Tuning Properties Using Population Receptive Field Mapping

Area of Science:

• Neuroscience
• Visual Perception
• Computational Neuroscience

Background:

• Binocular stereopsis is crucial for depth perception, utilizing horizontal retinal image offsets.
• The organization of binocular disparity tuning across the human visual cortex remains largely unknown.
• Previous research implicates multiple cortical areas in stereoscopic processing.

Purpose of the Study:

• To characterize neural tuning to binocular disparity across the human visual cortex.
• To investigate the relationship between disparity tuning and stereoacuity thresholds.
• To explore how different visual areas process varying degrees of binocular disparity.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to generate population receptive fields (pRFs) in response to modulated binocular disparity.
• Psychophysics measured stereoacuity thresholds using different pedestal disparities.
• Participants viewed correlated and anticorrelated random-dot stereograms with varying disparities.

Main Results:

• Lateral and dorsal visual areas exhibited the highest proportion of vertices selective for binocular disparity.
• A polynomial relationship was observed between preferred disparity and tuning curve width for correlated stimuli, with sharper tuning near zero disparity.
• This tuning relationship was absent for anticorrelated stimuli, and stereoacuity thresholds in V1 correlated with pRF tuning width.

Conclusions:

• Disparity processing shows heterogeneity across human visual areas, similar to nonhuman primates.
• The findings suggest that early visual processing in V1 may limit fine stereopsis.
• The study provides insights into the neural mechanisms underlying depth perception and disparity tuning.