Abstract

The lateral geniculate nucleus (LGN) in primates comprises cells with greatly varying numbers and contrast sensitivities. Cells in the magnocellular layers are approximately eight times more sensitive to luminance contrast than are the color-sensitive cells in the parvicellular layers. Parvicellular cells, on the other hand, outnumber magnocellular cells by approximately a factor of 10.^1,2 Kaplan and Shapley¹ report that these differences in contrast sensitivity result from differences in the sensitivity of the retinal ganglion cells that provide excitatory synaptic impulses to the LGN neurons. These cells, with varying sensitivities and densities, constitute an imagecoding scheme in which dense high-rate samples of an image with relatively low contrast sensitivity are supplemented with lower-density samples with better contrast sensitivity. If the few higher-contrast samples are sufficient to compensate for the low contrast of the densely populated cells when coding the image, then considerable dynamic contrast range can be saved.

© 1990 Optical Society of America