Single-Neuron Feature Detectors Area V1 contains neurons that respond to specific orientations of edges. Here a single neuron’s responses are recorded (below left) as the monkey views bars at different orientations (below right). This neuron fires continuously when the bar is pointing to the right at 45°, less often when it is vertical, and not at all when it is pointing to the left at 45°.

FRITZ GORO/TIME & LIFE PICTURES/GETTY IMAGES