Bottom-up saliency and top-down learning in the primary visual cortex of monkeys

Area of Science:

• Neuroscience
• Visual Perception
• Cognitive Science

Background:

• The role of early sensory cortex, particularly primary visual cortex (V1), in behavioral responses is less understood than its role in sensory input representation.
• Visual search tasks, like detecting an orientation singleton, involve processing visual stimuli and executing behavioral actions.

Purpose of the Study:

• To investigate the behavioral correlates of neuronal responses in V1 during a visual search task.
• To understand how learning and practice affect V1 activity and its relationship with behavior.

Main Methods:

• Monkeys were trained to detect an orientation singleton in a background of uniformly oriented bars.
• Neuronal activity in V1 was recorded using implanted microelectrodes during the singleton detection task.
• Behavioral performance (accuracy and speed) and V1 neuronal responses (early and late components) were analyzed in relation to orientation contrast and training.

Main Results:

• V1 neuronal responses to the singleton had early and late components that increased with orientation contrast.
• The early V1 response component was present before and after training, while the late component emerged and evolved with practice.
• Training improved detection performance and increased the information in the late V1 response about singleton presence; faster detection correlated with higher early V1 responses, a correlation strengthened by training.

Conclusions:

• Early V1 responses are directly linked to behavior, representing bottom-up saliency signals.
• Learning strengthens the link between early V1 responses and behavior, potentially making detection more reflexive.
• Late V1 responses are influenced by learning and contribute to improved task performance.