Another Blue-ON ganglion cell in the primate retina.

A classic and highly influential model of visual processing proposes that the role of the retina is to compress visual information for optimal transmission to the brain [1]. Drawing on ideas from information theory, an efficient retinal code could be defined as one that reduces redundancy to communicate as much information as possible, given the optic nerve's limited capacity. From this redundancy reduction hypothesis, a theory of retinal color coding emerged in which the three most common retinal ganglion cell (RGC) types captured much of the variance in natural spectra [2]. Within this compact code, the 'Blue-ON' small bistratified RGC was thought to be the only pathway necessary for comparing short (S) wavelength-sensitive cones to long (L) and medium (M) wavelength-sensitive cones [3,4]. Here, we discovered a new wide-field RGC type receiving the same cone-opponent input as the small bistratified RGC, indicating that there is more redundancy in the retinal color code than previously appreciated.