Task Context Modulates Feature-Selective Responses in Area V4.

Area of Science:

• Neuroscience
• Visual Cortex Research
• Primate Neurophysiology

Background:

• Neuronal selectivity in the visual cortex is typically measured during passive fixation.
• This passive measurement may not fully capture how cognitive factors, like task engagement, influence neuronal responses.
• Understanding these influences is crucial for a complete picture of visual processing.

Purpose of the Study:

• To investigate how neuronal tuning in primate area V4 is modulated by task engagement.
• To determine if responses to colored shapes during active discrimination are simple scaled versions of passive responses or if they exhibit stimulus-specific scaling.
• To explore changes in shape and color selectivity during active behavior.

Main Methods:

• Recorded responses from 83 well-isolated neurons in area V4 of two male macaques.
• Compared neuronal responses during passive fixation to responses during an active shape discrimination task.
• Analyzed stimulus-agnostic versus stimulus-specific scaling of neuronal responses based on shape and color features.

Main Results:

• A minority of V4 neurons (16/83) showed stimulus-agnostic scaling between passive fixation and active discrimination.
• The majority of neurons (67/83), particularly those strongly tuned to shape or color, exhibited stimulus-dependent response changes.
• For strongly tuned neurons, task engagement amplified selectivity for the dominant feature, altering the balance of shape and color tuning without shifting tuning peaks.

Conclusions:

• Neuronal responses in area V4 are significantly modulated by task engagement in a stimulus-dependent manner.
• Strongly tuned V4 neurons demonstrate flexibility, with selectivity dynamically adjusted based on task demands.
• This flexibility in feature selectivity may enhance performance in active visual judgment tasks.