NEURAL CORRELATES OF PERCEPTUAL SIMILARITY MASKING IN PRIMATE V1

Area of Science:

• Neuroscience
• Computational Neuroscience
• Vision Science

Background:

• Visual detection is fundamental, but challenged by "similarity masking" where target-background similarity hinders detection.
• The role of the primary visual cortex (V1) in similarity masking remains unclear.

Approach:

• Used voltage-sensitive dye imaging (VSDI) to record V1 population activity in macaques performing a visual detection task.
• Manipulated target-background similarity to observe its effect on V1 responses.
• Developed a computational model with delayed divisive normalization to interpret findings.

Key Points:

• Paradoxically, V1 responses to targets were enhanced by similarity during an initial transient phase.
• This enhancement reversed in a later phase, where V1 signals correlated with behavioral similarity masking.
• A model incorporating delayed divisive normalization qualitatively reproduced these V1 response dynamics.

Conclusions:

• V1 exhibits complex, time-varying responses to target-background similarity.
• Findings support the hypothesis that V1's nonlinear gain control contributes to perceptual similarity masking.
• This research offers insights into the neural mechanisms underlying visual perception and challenges.