Fang Fang’s group used the psychophysical adaptation paradigm to explore the predictive coding mechanism for human visual cortex by measuring the moderating effect of perceptual grouping for high-level and low-level visual aftereffect. The study not only reveals a new function of primary visual cortex, providing the first psychophysical evidence for the predictive coding model, but also challenges the dominant view of perceptual grouping that perceptual grouping enhances the neural responses throughout the visual processing hierarchy.

He D., Kersten D., and Fang F. (2012). Opposite modulation of high- andlow-level visual aftereffects by perceptual grouping. Curr  Biol  22: 104 0-1045.