GABA-inactivation attenuates colinear facilitation in cat primary visual cortex.

Area of Science:

• Neuroscience
• Visual Processing
• Computational Neuroscience

Background:

• Neurons in the primary visual cortex (V1) have receptive fields (RFs) that respond to specific stimulus orientations.
• Contextual effects, like collinear facilitation, enhance neuronal responses to stimuli within the RF when aligned with stimuli outside the RF.
• Collinear facilitation is thought to integrate contour elements and enhance perceptual saliency.

Purpose of the Study:

• To investigate the role of horizontal connections in collinear facilitation in cat area V1.
• To determine if laterally remote V1 cells contribute to collinear facilitation.

Main Methods:

• Single-cell recordings in cat area V1.
• Focal inactivation of specific V1 neuronal populations.
• Presentation of optimally oriented stimuli within RFs and co-oriented flank stimuli outside RFs.

Main Results:

• Focal inactivation of laterally remote V1 cells significantly reduced or abolished collinear facilitation.
• Cells responding to flank stimuli were identified as targets for inactivation.
• This demonstrates the contribution of horizontal connections to collinear facilitation.

Conclusions:

• Horizontal intrinsic connections between V1 cells with co-oriented and co-linearly aligned RFs significantly contribute to collinear facilitation.
• The neuronal circuitry for contour integration and saliency is present at the earliest stage of visual cortical processing (V1).
• These findings provide physiological evidence for the role of local horizontal connections in early visual processing and contour perception.