To describe the wide-field ganglion cells, they were injected
intracellularly with Neurobiotin using an in vitro preparation of
macaque retina and labeled with streptavidin-Cy3. The retinas were then
labeled with antibodies to choline acetyltransferase and other markers to
indicate the depth of the dendrites within the inner plexiform layer (IPL)
and analyzed by confocal microscopy. There were eight different subtypes
of narrowly unistratified cells that ramified in each of the 5 strata,
S1–5, including narrow thorny, large sparse, large moderate, large
dense, large radiate, narrow wavy, large very sparse, and fine very
sparse. There were four types of broadly stratified cells with dendritic
trees extending from S4 to S2. One type resembled the parvocellular giant
cell and another the broad thorny type described previously in primates.
Another broadly stratified cell was called multi-tufted based on its
distinctive dendritic branching pattern. The fourth type had been
described previously, but not named; we called it broad wavy. There was a
bistratified type with its major arbor in S5, the same level as the blue
cone bipolar cell; it resembled the large, bistratified cell with blue
ON-yellow OFF responses described recently. Two wide-field ganglion cell
types were classified as diffuse because they had dendrites throughout the
IPL. One had many small branches and was named thorny diffuse. The second
was named smooth diffuse because it had straighter dendrites that lacked
these processes. Dendrites of the large moderate and multi-tufted cells
cofasciculated with ON-starburst cell dendrites and were, therefore,
candidates to be ON- and ON–OFF direction-selective ganglion cells,
respectively. We concluded that there are at least 15 morphoplogical types
of wide-field ganglion cells in macaque retinas.