Modular Representation of Luminance Polarity in the Superficial Layers of Primary Visual Cortex

The spatial arrangement of luminance increments (ON) and decrements (OFF) falling on the retina provides a wealth of information used by central visual pathways to construct coherent representations of visual scenes. But how the polarity of luminance change is represented in the activity of cortical circuits remains unclear. Using wide-field epifluorescence and two-photon imaging we demonstrate a robust modular representation of luminance polarity (ON or OFF) in the superficial layers of ferret primary visual cortex. Polarity-specific domains are found with both uniform changes in luminance and single light/dark edges, and include neurons selective for orientation and direction of motion. The integration of orientation and polarity preference is evident in the selectivity and discrimination capabilities of most layer 2/3 neurons. We conclude that polarity selectivity is an integral feature of layer 2/3 neurons, ensuring that the distinction between light and dark stimuli is available for further processing in downstream extrastriate areas. •A modular map of luminance polarity (ON/OFF) exists in visual cortex layer 2/3•Both edge and uniform luminance stimuli activate polarity preference domains•Orientation selectivity of layer 2/3 neurons is polarity dependent•Primary visual cortex preserves polarity signals for downstream cortical areas Smith et al. demonstrate that edge and uniform luminance stimuli activate modular maps of luminance polarity (dark versus light) in layer 2/3 of primary visual cortex. Individual neurons integrate polarity with orientation, preserving polarity specific signals for downstream cortical areas.