Delayed suppression shapes disparity selective responses in monkey V1.

Area of Science:

• Neuroscience
• Computational Neuroscience
• Vision Science

Background:

• The stereo correspondence problem challenges visual neurons due to localized receptive fields causing potential false positives.
• Neurons in the primary visual cortex (V1) integrate excitatory and suppressive signals to encode binocular disparity, partially resolving this issue.

Purpose of the Study:

• To investigate the temporal dynamics of excitatory and suppressive response combinations in awake, monkey V1 neurons.
• To elucidate the role of suppressive mechanisms in resolving the stereo correspondence problem and explain signal mismatches.

Main Methods:

• Utilized subspace mapping of receptive fields in awake, behaving monkey V1 neurons.
• Employed a binocular noise pattern stimulus with discrete spatial frequency components.
• Applied forward correlation to analyze V1 neuron firing in response to spatial frequency and interocular phase differences.

Main Results:

• Identified combinations of spatial frequency and interocular phase differences that elicited suppressive responses.
• Observed that suppression at lower spatial frequencies was typically delayed by approximately 7 ms relative to excitation at higher spatial frequencies.
• Demonstrated that suppressive components enhanced low spatial frequency power in disparity tuning while reducing monocular responses to low spatial frequencies.

Conclusions:

• A delayed suppressive mechanism is crucial for resolving the stereo correspondence problem in V1.
• This suppressive mechanism explains the long-observed mismatch between monocular and binocular signals.
• The findings highlight how V1 neurons refine disparity encoding by suppressing false matches, particularly at low spatial frequencies.