Center-surround antagonism based on disparity in primate area MT

Area of Science:

• Neuroscience
• Computational Neuroscience
• Visual Perception

Background:

• Neurons in primate visual area MT possess a receptive field center and a surrounding modulatory region.
• The surround typically exhibits velocity tuning antagonistic to the center, aiding in the detection of motion-based image discontinuities.
• Given MT neurons' disparity selectivity, a similar disparity-based antagonism in the surround was hypothesized but uninvestigated.

Purpose of the Study:

• To investigate the role of disparity in the modulatory surround of primate visual area MT neurons.
• To determine if surround disparity influences neuronal responses and contributes to image segmentation.

Main Methods:

• Single-neuron responses were recorded in the MT surround of primates.
• Neurons were stimulated with moving patterns at varying disparities in the surround while a central pattern was held at a fixed disparity.
• The effects of surround disparity on neuronal responses were analyzed in relation to disparity and direction selectivity.

Main Results:

• A modulatory surround was present in 84% of the 130 tested neurons.
• Disparity in the surround significantly affected responses in 52% of neurons with modulatory surrounds.
• Surround disparity effects were predominantly antagonistic to the center, with suppression decreasing as depth separation increased. Disparity and direction effects were largely additive.

Conclusions:

• The MT center-surround organization provides information about image discontinuities based on both velocity and depth differences.
• The findings support the hypothesis that MT surrounds play a crucial role in image segmentation by processing depth disparities.
• This research highlights the importance of surround mechanisms in complex visual processing within area MT.