Spatial attention, feature-based attention, and biased competition in visual cortex
Spatial attention acts as a "spotlight" (Posner, 1980): neural responses in retinotopic areas (V1, V4, MT) are enhanced for stimuli at the attended location and suppressed elsewhere. The biased competition model (Desimone & Duncan, 1995) explains this as competitive filtering: multiple stimuli compete for neural representation, and top-down attention biases this competition in favor of the attended item via feedback from prefrontal and parietal cortex. Feature-based attention (e.g., attending to color or orientation) modulates responses globally across the visual field, while spatial attention is retinotopically specific. Click anywhere on the canvas to move the attention spotlight.