The Diversity of Ganglion Cells in a Mammalian Retina

Abstract

We report a survey of the population of ganglion cells in the rabbit retina. A random sample of 301 neurons in the ganglion cell layer was targeted for photofilling, a method in which the arbors of the chosen neurons are revealed by diffusion of a photochemically induced fluorescent product from their somas. An additional 129 cells were labeled by microinjection of Lucifer yellow. One hundred and thirty-eight cells were visualized by expression of the gene encoding a green fluorescent protein, introduced by particle-mediated gene transfer. One hundred and sixty-six cells were labeled by particle-mediated introduction of DiI. In the total population of 734 neurons, we could identify 11 types of retinal ganglion cell. An analysis based on retinal coverage shows that this number of ganglion cell types would not exceed the available total number of ganglion cells. Although some uncertainties remain, this sample appears to account for the majority of the ganglion cells present in the rabbit retina. Some known physiological types could easily be mapped onto structural types, but half of them could not; a large set of poorly known codings of the visual input is transmitted to the brain.

Stratification of alpha ganglion cells and ON/OFF directionally selective ganglion cells in the rabbit retina

“…The small details, concerning either a difference in depth of a few microns or subtle variations in branch pattern among ganglion cell types, seem to be important. Our results strongly suggest that a specific ganglion cell type is stratified at a precise depth in the IPL and this confirms the work of others who have studied different ganglion cell types (Roska & Werblin, 2001;Rockhill et al, 2002;Famiglietti, 2004).…”

“…The α ganglion cells seem identical to the type 11 ganglion cells in the survey reported by Rockhill et al (2002). However, in this survey, they are drawn as rather broadly stratified, through and beyond the ON/OFF DS or cholinergic bands.…”

“…It could be argued that stratification at a different depth, say above instead of below one of the cholinergic bands, would provide different inputs and thus such a ganglion cell would be a different type. We note that another ganglion cell, type 9, in the Rockhill et al (2002) classification is depicted as branching just above cholinergic a.…”

“…The number of cone bipolar cell types in the mammalian retina is usually given between 10 and 12, plus one for the rod bipolar cells (Haverkamp et al, 2003;Ghosh et al, 2004;MacNeil et al, 2004), and there is strong evidence that different bipolar cell types have different physiological properties, thus splitting the photoreceptor signals into different channels (DeVries, 2000). The number of ganglion cell types has been estimated as 13 or 14, but there is usually an unclassified remainder which could include a number of sparse or low-density cell types (Rockhill et al, 2002;Marc & Jones, 2002;Dacey et al, 2003;Yamada et al, 2005). This may boost the total number of types to between 15 and 20.…”

“…Morphological, physiological, and biochemical analyses of ganglion cells all suggest that there are around 12-15 different types (Caldwell & Daw, 1978;DeVries & Baylor, 1997;Marc & Jones, 2002;Rockhill et al, 2002). Each ganglion cell type is thought to carry a separate channel of visual signals but the morphological classification of ganglion cell types has been difficult.…”