Bipolar cells in monkey retina selective for the cones likely to be blue-sensitive

Bipolar cells are a class of retinal interneurone with dendrites in the outer plexiform layer that contact photoreceptors, and axons terminating in the inner plexiform layer where they convey the centre responses of ganglion cells. In the monkey, many of whose ganglion cells respond to stimuli selective for each of the three different cones. There are five types of cone bipolar cells: flat and invaginating midget; diffuse, flat and invaginating cone; and giant, bistratified. Although many of the monkey's ganglion cells are specific for one of the three different cone mechanisms, none of the bipolar cells are known to connect to the morphologically identified counterparts of the different spectral types of cones as in teleost retina. Here, however, I describe a bipolar cell found in Golgi preparations of the rhesus monkey retina which displays an apparently selective and patterned distribution of its dendritic contacts with cone pedicles in the outer plexiform layer. The intercone spacing of dendritic contacts and their distribution match the intercone spacing and proportion of cones thought to be blue-sensitive.