Ehud Kaplan on Receptive fields

[jinglescode]

Paper

Link: https://scholar.google.com/citations?user=gyugy60AAAAJ&hl=en&oi=sra
Year:

• There are approximately 1 million retinal ganglion cells (RGCs) in the human retina but their number tends to decrease with aging
• three main RGC types, the Magnocellular projecting cells (M-cells), Parvocellular projecting cells (P-cells) and Koniocellular (K-) cells
• two main classes of primate RGCs, the M-cells and the P-cells

M-cells

• M-cells, also called parasol cells, have larger receptive fields, respond better to large, coarse objects than the P-cells
• M-cells are about two to three times larger in diameter than the P-cells at any given retinal eccentricity
• make up of approximately 10% of the total RGCs
• M-cells are shown to be 8-10 times more sensitive to low achromatic contrast than the small P-cells
• respond somewhat better to high temporal frequencies (motion) and low spatial frequencies
• M-cells are also more sensitive than P-cells to achromatic stimuli
• Since M-cells are relatively fewer in numbers and more sparsely distributed than P-cells, they have less redundancy - there is limited overlapping coverage of the visual field, therefore if for example there is a loss of function just a few of these cells, there will be a location of the VF where there are no cells available to sense the target
• magnocellular pathway cannot provide finely detailed or colored information, but still provides useful static, depth, and motion information (wiki)
• M pathway has high light/dark contrast detection, and is more sensitive at low spatial frequencies than high spatial frequencies (wiki)

P-cells

• or midget cells, project to the four Parvocellular layers of the LGN
• have relatively smaller cell bodies and dendritic trees
• make up of approximately 80% of the total RGCs
• P-cells are relatively more sensitive to low temporal and high spatial frequencies than the M-cells
• respond quite linearly from low to high grating contrasts
• respond best to chromatic especially red or green colours
• parvocellular neurons are sensitive to colour, and are more capable of discriminating fine details than their magnocellular counterparts (wiki)
• Parvocellular cells have greater spatial resolution, but lower temporal resolution, than the magnocellular cells (wiki)

Parvocellular (P-cells)	Magnocellular (M-cells)
Low temporal frequency	High temporal frequency
High spatial frequency	Low spatial frequency
High contrast threshold	Low contrast threshold (Lee, Wehrhahn et al. 1995)
Low contrast gain (low contrast sensitivity); Linear response to 100% (Kaplan and Shapley 1986)	High contrast gain (up to 10 times more than P-cells; Response saturates at 15-20 % contrast (Kaplan and Shapley 1986)
Responds more strongly to chromatic than achromatic stimuli especially red/green	Responds best to achromatic stimuli (luminance contrast)