 Some things may be as simple as black and white. The circuits in the brain that allow us to distinguish black from white, however, are not. The basic difference between bright and dark provides a well-to-visual information that is sent from the retina to the brain. But how information about bright and dark is processed in the visual cortex, a part of the brain that helps build the neural representations that are responsible for sight, was not fully clear. By using a highly sensitive imaging method, researchers recently showed that bright and dark are processed in separate channels in the superficial layers of the primary visual cortex. On cells in the retina respond selectively to bright stimuli, and off cells respond selectively to dark. From these cells, information about bright and dark enters the brain through separate channels. However, once the on and off pathways enter the visual cortex, the processing of light and dark gets murky. Neurons in the superficial layers of the cortex, which is the main pathway to the higher-order visual areas that create our perception of the visual world, seem to receive mixed information from both the on and off pathways. If this is the case, how does the brain allow us to perceive differences in bright and dark? Doctors Gordon Smith and David Whitney in David Fitzpatrick's lab at Moxplonk, Florida Institute for Neuroscience addressed this question using a highly sensitive calcium imaging method that enables the activity of hundreds of neurons in the living brain to be visualized simultaneously. They were able to quantify the responses of neurons in the ferret visual cortex to bright and dark. Surprisingly, they found that the majority of superficial layer neurons responded preferentially to bright or dark. Even more surprisingly, the neurons that responded to bright or dark were clustered together in patches, indicating that the on and off channels were preserved in the superficial layers. Because neurons in the visual cortex are so strongly selective for the orientation of edges, which define objects and help us make sense of visual scenes, the researchers also used edges to explore the relationship between the encoding of orientation and the encoding of dark and bright. They found that the responses of superficial layer neurons depended strongly on both edge orientation and whether the edge was bright or dark, indicating that both properties are jointly encoded in the superficial layers. In short, the team discovered that information about dark and bright is preserved in the responses of most neurons in the visual cortex. The robust encoding of bright and dark in the visual cortex ensures that this information remains available to higher-order perceptual regions, helping us to recognize objects and detect motion. Further studies are required to determine the precise circuit mechanisms that generate the selectivity for bright and dark in this layer.