Preemptive gain control in primary visual cortex.

Area of Science:

• Neuroscience
• Visual Neuroscience
• Computational Neuroscience

Background:

• Neurons adapt to environmental stimuli via gain control, like contrast normalization in the visual cortex.
• Contrast normalization optimizes processing for current visual input but is suboptimal for future, unknown inputs after eye movements.

Purpose of the Study:

• To test the hypothesis that preemptive reset of the contrast response function during saccades resolves the conflict between current and future visual needs.
• To investigate the role of saccades in gain control mechanisms within the primary visual cortex.

Main Methods:

• Multi-electrode array recordings in the primary visual cortex of macaque monkeys.
• Analysis of neural responses to varying contrast levels during fixation and saccades.

Main Results:

• High contrast during fixation reduced neural gain and compressed the contrast response function.
• During saccades, gain changes were partially reversed, leading to higher gain and a broader, more linear response.
• Pre-saccadic gain decreases and post-saccadic gain increases were anticorrelated, suggesting a shared underlying mechanism.

Conclusions:

• The biphasic peri-saccadic neural response is a signature of a pause-rebound mechanism that resets the contrast response function for future visual input.
• This preemptive gain control strategy prepares the visual system for novel stimuli encountered after saccades.
• Saccadic suppression, a reduction in visual sensitivity before eye movements, is reinterpreted as a consequence of this advantageous signal-processing strategy.