A collaborative study between University of California, Berkeley and the Allen Institute has identified a subset of neurons in the primary visual cortex that specifically encode illusory contours—shapes perceived despite absence in the stimulus. Using advanced tools such as two-photon holographic optogenetics in mice, researchers pinpointed and stimulated these neurons, demonstrating their causal role in pattern completion and visual inference. These findings elucidate how top-down signals from higher visual areas integrate with primary sensory cortex to generate perception beyond raw inputs.