Earlier work had hinted at such cells, but Shin and colleagues show systematically that they’re not rare oddballs—they’re a well-defined, functionally important subpopulation. “What we didn’t know is that these neurons drive local pattern completion within primary visual cortex,” says Shin. “We showed that those cells are causally involved in this pattern completion process that we speculate is likely involved in the perceptual process of illusory contours,” adds Adesnik. Behavioral tests still ...