The 'blue-on' opponent pathway in primate retina originates from a distinct bistratified ganglion cell type

Abstract

Colour vision in humans and Old World monkeys begins with the differential activation of three types of cone photoreceptor which are maximally sensitive to short (S), medium (M) and long (L) wavelengths. Signals from the three cone types are relayed to the retinal ganglion cells via cone-specific bipolar cell types. Colour-coding ganglion cells fall into two major physiological classes: the red-green opponent cells, which receive antagonistic input from M- and L-sensitive cones, and the blue-yellow opponent cells, which receive input from S-sensitive cones, opposed by combined M- and L-cone input. The neural mechanisms producing colour opponency are not understood. It has been assumed that both kinds of opponent signals are transmitted to the lateral geniculate nucleus by one type of ganglion cell, the midget cell. We now report that a distinct non-midget ganglion cell type, the small bistratified cell, corresponds to the physiological type that receives excitatory input from S cones, the 'blue-on' cell. Our results thus demonstrate an anatomically distinct pathway that conveys S-cone signals to the brain. The morphology of the blue-on cell also suggests a novel hypothesis for the retinal circuitry underlying the blue-yellow opponent response.

Identification and Characterization of a Y-Like Primate Retinal Ganglion Cell Type

“…This fraction is measured to be 4.4 Ϯ 4.1%, based on the peak of the S-cone time filter response relative to the peak of the S-cone plus (L ϩ M)-cone response, and including an estimated cross talk of 0 Ϯ 4% between the S and (L ϩ M) cone-isolating stimuli. For comparison, the corresponding S-cone fraction measured for S-ON/(L ϩ M)-OFF cells [most likely small bistratified blue/yellow color opponent cells (Dacey and Lee, 1994)] in the same preparation is 48.4 Ϯ 16.6%, indicating that the S-cones were functioning normally (data not shown). (This insignificant S-cone input to upsilon cells, measured in the presence of simultaneously recorded S-ON/(L ϩ M)-OFF cells, was also observed in several preparations that contained only a few upsilon cells and therefore were not included in this paper.)…”

“…Although decades of work have been devoted to the study of primate retinal architecture, fewer than one-half of the 22 or more anatomically identified types of retinal ganglion cells (RGCs) (Rodieck and Watanabe, 1993;Dacey et al, , 2005Dacey, 2004;Yamada et al, 2005) have been characterized physiologically, namely the ON and OFF midget and parasol cells (Dacey, 1999;Chichilnisky and Kalmar, 2002), the small bistratified cells (Dacey and Lee, 1994;Chichilnisky and Baylor, 1999), the recently discovered giant sparse (melanopsin-expressing) cells (Dacey et al, , 2005Dacey, 2004), and, to some extent, the large bistratified cells and the cells of type "sparse" Dacey, 2004). One of the possible reasons for this discrepancy is that the morphological RGC types awaiting physiological characterization constitute only a small fraction of all the primate ganglion cells (1-4%) [see Dacey (2004), their table 20.1].…”

How long range is contour integration in human color vision?

“…It is worth noting that this effect was also accompanied by a perceptual melting of the BY elements, in which the elements appear ill-defined and "melt" into the background. We hypothesized that the larger occupancy radius, perceptual melting effect, and density bias of the BY signal point to spatial processing differences among the postreceptoral mechanisms, which may include differences in their spatial filters, the sparseness of their spatial sampling, and differences in intracortical connectivity (Curcio et al, 1991;Dacey & Lee, 1994; Calkins , 1998). When comparing with the present experiment, it is also noteworthy that the critical separation for contour integration is about 3.5 times the occupancy diameter for the Ach mechanism, and only 1.5 times for the BY mechanism (Table 1).…”

Strategies to improve early diagnosis in glaucoma

“…It was initially thought that SWAP targets parvocellular blue-yellow retinal ganglion cells projecting to the parvocellular layers of the lateral geniculate nucleus, i.e., the parvocellular (P) pathway. However, it was later shown that blue-yellow cells are in fact small bistratified ganglion cells, which project their axons to the koniocellular layers of the lateral geniculate nucleus (Dacey and Lee, 1994;Sample et al, 2006). Several studies have compared the ability of SAP, SWAP, and/or FDT to detect glaucoma but have shown divergent results Medeiros et al, 2006;Sample et al, 2006;Tafreshi et al, 2009).…”