A Pixel-Encoder Retinal Ganglion Cell with Spatially Offset Excitatory and Inhibitory Receptive Fields

SUMMARY

The spike trains of retinal ganglion cells (RGCs) are the only source of visual information to the brain. Here, we genetically identify an RGC type in mice that functions as a pixel encoder and increases firing to light increments (Pix _ON-RGC). Pix _ON-RGCs have medium-sized dendritic arbors and non-canonical center-surround receptive fields. From their receptive field center, Pix _ON-RGCs receive only excitatory input, which encodes contrast and spatial information linearly. From their receptive field surround, Pix _ON-RGCs receive only inhibitory input, which is temporally matched to the excitatory center input. As a result, the firing rate of Pix _ON-RGCs linearly encodes local image contrast. Spatially offset (i.e., truly lateral) inhibition of Pix _ON-RGCs arises from spiking GABAergic amacrine cells. The receptive field organization of Pix _ON-RGCs is independent of stimulus wavelength (i.e., achromatic). Pix _ON-RGCs project predominantly to the dorsal lateral geniculate nucleus (dLGN) of the thalamus and likely contribute to visual perception.

In Brief

Johnson et al. genetically identify a pixel-encoder retinal ganglion cell type in mice (Pix _ON-RGCs). Pix _ON-RGCs have spatially offset excitatory and inhibitory receptive fields and encode local image contrast approximately linearly. Their axons project to the dorsolateral geniculate nucleus of the thalamus indicating that Pix _ON-RGCs likely contribute to visual perception.