Journal of Vision ;5 12 Psychophysical evidence suggests that humans are similar 2,3. Thus, there are 2 S-cone ON bipolar cells for each S cone 5. Due to the uneven distribution of synapses in this pathway, one of these two BY ganglion cells is likely to be narrow field, dominated by just one S cone, and one is likely to be wide field, driven strongly by several S cones 6. Relation to color vision: It has been suggested 8 that efficient coding of color signals from three spectrally overlapping and thus correlated cone signals requires three postreceptoral pathways, a spectrally unimodal one achromatic , a spectrally bimodal one blue-yellow , and a spectrally trimodal one red-green-red 9.
Bipolar Cell Pathways in the Vertebrate Retina by Ralph Nelson and Victoria Connaughton
Complexity of retinal cone bipolar cells
To date, 12 macaque bipolar cell types have been described. This list includes all morphology types first outlined by Polyak using the Golgi method in the primate retina and subsequently identified by other researchers using electron microscopy EM combined with the Golgi method, serial section transmission EM SSTEM , and immunohistochemical imaging. Retinal circuits formed by GB and DB3b cells are thought to substantiate the psychophysical finding of fast rod signals in mesopic vision. Vertebrate retina's bipolar cells terminate close to the photoreceptor layer with one polar neurite and to the ganglion cell layer with the other polar neurite.
Retina bipolar cell
The specialized cone pathways of the central fovea of human and monkey retinas have the least convergence and the greatest resolution capabilities of the visual system. Figure 1. The illustration is taken from Polyak, The midget pathways consist of midget bipolar cells and midget ganglion cells, the latter of which project to individual parvocellular layer cells of the lateral geniculate nucleus in the brain.
Journal of Neurocytology. The photoreceptor synapses of three representative cells of the six types of diffuse bipolar cell of the rhesus macaque monkey's retina are described at 3. Bipolar cell DB4 was postsynaptic to eight cones at 52 ribbon synapses; in addition it was found also to make an average of two or three basal non-ribbon synapses per cone total The DB5 bipolar cell type had 57 invaginating synapses with seven cones. It too had basal synapses, but only two with each of three cones.