Neuronal mechanisms underlying stereopsis: how do simple cells in the visual cortex encode binocular disparity?

Area of Science:

• Neuroscience
• Visual Perception
• Computational Neuroscience

Background:

• Binocular neurons in the visual cortex are crucial for stereoscopic depth perception.
• The organization of receptive fields in these neurons encodes retinal position disparities from binocular parallax.
• Conventional models propose identical receptive field shapes spatially offset for disparity encoding.

Purpose of the Study:

• To investigate an alternative disparity-encoding scheme where receptive fields may differ in shape but are centered at corresponding retinal locations.
• To determine how receptive field organization in binocular neurons contributes to stereopsis.
• To challenge and refine the traditional understanding of the neural basis of stereopsis.

Main Methods:

• Utilized a reverse-correlation technique to generate detailed spatiotemporal receptive-field maps.
• Analyzed receptive field profiles of binocular neurons in the striate cortex.
• Compared receptive field shapes for left and right eyes in neurons tuned to horizontal versus vertical contours.

Main Results:

• Receptive field profiles were matched for neurons tuned to horizontal contours.
• For neurons tuned to vertical contours, left and right receptive fields predominantly showed dissimilar shapes.
• Demonstrated that the striate cortex has specialized mechanisms for processing vertical contours.

Conclusions:

• The findings support a model where binocular receptive fields can differ in shape (phase) while being centered at corresponding retinal locations.
• Proposed that binocular simple cells encode horizontal disparities using phase information across multiple spatial scales.
• Suggests a significant modification to the traditional view of neural mechanisms underlying stereopsis, particularly concerning vertical contour processing.