Cardinal orientation selectivity is represented by two distinct ganglion cell types in mouse retina

Orientation selectivity (OS) is a prominent and well studied feature of early visual processing in mammals, but recent work has highlighted the possibility that parallel OS circuits might exist in multiple brain locations. Although both classic and modern work has identified an OS mechanism in selective wiring from lateral geniculate nucleus (LGN) to primary visual cortex, OS responses have now been found upstream of cortex in mouse LGN and superior colliculus, suggesting a possible origin in the retina. Indeed, retinal OS responses have been reported for decades in rabbit and more recently in mouse. However, we still know very little about the properties and mechanisms of retinal OS in the mouse, including whether there is a distinct OS ganglion cell type, which orientations are represented, and what are the synaptic mechanisms of retinal OS. We have identified two novel types of OS ganglion cells in the mouse retina that are highly selective for horizontal and vertical cardinal orientations. Reconstructions of the dendritic trees of these OS ganglion cells and measurements of their synaptic conductances offer insights into the mechanism of the OS computation at the earliest stage of the visual system.