Which statement correctly describes contrast sensitivity and center-surround receptive fields in the primary visual cortex?

Which statement correctly describes contrast sensitivity and center-surround receptive fields in the primary visual cortex?

• A. False; center-surround organization is not involved in edge detection.
• B. Contrast sensitivity relates to detecting luminance differences; V1 uses center-surround receptive fields and orientation-selective cells for edge detection.
• C. Contrast sensitivity relies solely on color channels.
• D. Receptive fields in V1 are non-orientation selective.

Answer: (B)

Edge detection in the visual system hinges on detecting luminance differences, not just color. In the primary visual cortex, neurons often have center-surround receptive fields that respond to local contrasts: the center region excites while the surrounding region inhibits (or vice versa). When a luminance edge falls across such a receptive field, the balance between center and surround changes, producing a stronger signal that highlights the border between light and dark. Adding to this, many V1 neurons are orientation-selective. Their receptive fields are elongated and tuned to specific angles, so edges at the neuron’s preferred orientation elicit a robust response. This combination—center-surround contrast sensitivity plus orientation-selective responses—enables precise edge detection. The statement that contrast sensitivity relies solely on color channels is not accurate, and the idea that V1 receptive fields are non-orientation selective is incorrect.

Edge detection in the visual system hinges on detecting luminance differences, not just color. In the primary visual cortex, neurons often have center-surround receptive fields that respond to local contrasts: the center region excites while the surrounding region inhibits (or vice versa). When a luminance edge falls across such a receptive field, the balance between center and surround changes, producing a stronger signal that highlights the border between light and dark.

Adding to this, many V1 neurons are orientation-selective. Their receptive fields are elongated and tuned to specific angles, so edges at the neuron’s preferred orientation elicit a robust response. This combination—center-surround contrast sensitivity plus orientation-selective responses—enables precise edge detection. The statement that contrast sensitivity relies solely on color channels is not accurate, and the idea that V1 receptive fields are non-orientation selective is incorrect.