Introduction
The perception of complex visual patterns emerges from neuronal activity in a cascade of areas in the primate cerebral cortex. Neurons in the primary visual cortex (V1) represent information about basic image features like local orientation and spatial scale. Downstream areas contain neurons sensitive to more complex properties, especially those found in behaviorally-relevant, natural images. But sensitivity to these naturalistic structures requires transformations of basic visual signals, which have been difficult to characterize in computational or physiological terms.
The role of the second visual area (V2) has been particularly enigmatic. V2 is the largest extrastriate visual cortical area in primates, and its responses depend on feedforward input from V1 \citet{6288886}