Synaptic inputs onto small bistratified (blue‐ON/yellow‐OFF) ganglion cells in marmoset retina

Abstract

The inner plexiform layer of the retina contains functional subdivisions, which segregate ON and OFF type light responses. Here, we studied quantitatively the ON and OFF synaptic input to small bistratified (blue-ON/yellow-OFF) ganglion cells in marmosets (Callithrix jacchus). Small bistratified cells display an extensive inner dendritic tier that receives blue-ON input from short-wavelength-sensitive (S) cones via blue cone bipolar cells. The outer dendritic tier is sparse and is thought to receive yellow-OFF input from medium (M)- and long (L)-wavelength-sensitive cones via OFF diffuse bipolar cells. In total, 14 small bistratified cells from different eccentricities were analyzed. The cells were retrogradely labeled from the koniocellular layers of the lateral geniculate nucleus and subsequently photofilled. Retinal preparations were processed with antibodies against the C-terminal binding protein 2, the AMPA receptor subunit GluR4, and/or gephyrin to identify bipolar and/or amacrine input. The results show that the synaptic input is evenly distributed across the dendritic tree, with a density similar to that reported previously for other ganglion cell types. The population of cells showed a consistent pattern, where bipolar input to the inner tier is about fourfold greater than bipolar input to the outer tier. This structural asymmetry of bipolar input may help to balance the weight of cone signals from the sparse S cone array against inputs from the much denser M/L cone array.

Color signals through dorsal and ventral visual pathways

“…Whether this difference is relevant is unclear, but the conflicting results cast some doubt on whether S-cone signals actually penetrate MT. Anatomical evidence suggests they do: S cones may enter MT by way of diffuse bipolar cells (Dacey & Lee, 1994; Dacey, 1996; Calkins et al , 1998; Klug et al , 2003; Percival et al , 2009), which provide the excitatory input to parasol ganglion cells and LGN magnocellular cells. This evidence implies that diffuse bipolar cells and magnocellular cells should respond to S-cone-isolating stimuli, but physiological studies have not been able to confirm this prediction conclusively (Derrington et al , 1984; Chatterjee & Callaway, 2002; Reid & Shapley, 2002; Sun et al , 2006; Dacey et al , 2013).…”

Functional architecture of the retina: Development and disease

“…About half of the amacrine cells in the mammalian retina are wide-field GABAergic amacrine cells (Pourcho and Goebel, 1983; Wässle and Boycott, 1991) whereas the other half are small-field glycinergic amacrine cells (Pourcho and Goebel, 1985, 1987; Pow et al, 1995; Wässle et al, 1986). A recent study, however, revealed that there are amacrine cells that are neither GABAergic nor glycinergic (Kay et al, 2011).…”

“…Moreover, this I/E ratio remained comparable across different eccentricities (Abbott et al, 2012). Interestingly, the bistratified (blue-ON, yellow-OFF) ganglion cell in marmoset retina displays a characteristic pattern in arranging its excitatory synapses: bipolar cell input to the ON-arbor is about 4 times greater than input to the OFF arbor, but the ratio of the densities of bipolar cell input to both ON and OFF arbors remains the same across retinal eccentricities (Percival et al, 2009). Bipolar cell and amacrine cell inputs onto the dendrites of these bistratified cells were revealed by immunolabeling for a presynaptic ribbon marker or for GluA4 and for gephyrin, respectively (Percival et al, 2009).…”

A simpler primate brain: the visual system of the marmoset monkey

“…These in turn provide input to at least 15 morphological classes of retinal ganglion cell (Percival et al, 2009, 2011, 2013; Moritoh et al, 2013). In the marmoset, the peak ganglion cell density is ∼550,000 ganglion cells/mm 2 , so each foveal cone is sampled by at least two ganglion cells (Wilder et al, 1996).…”