Contribution of different lateral geniculate cell types to visual behavior

Abstract

The responses of primate lateral geniculate cells were studied in several experiments in which the stimulus situation was similar to that in various classical psychophysical discrimination experiments. Of interest were the role played by various cell type, and the extent to which the sub-cortical interactions can quantitatively account for various aspects of vision. 1. Different cell types. Evidence was presented for the existence of six different cell types, two spectrally non-opponent and four spectrally opponent. Evidence for the way in which the three cone types feed into the six LGN cell types was presented. 2. Presence of color discrimination. The non-opponent cells were shown to be “colorblind”, showing to change in firing with a shift from an achromatic to an equal-luminance monochromatic light. Opponent cells all make such discriminations, and in each case are dichromatic. 3. Brightness discrimination. All six cell types respond to increments and decrements of achromatic light, but the non-opponent cells are the most responsive. 4. Wavelength discrimination. The RG opponent cells discriminate wavelengths best around 600 nm, and the YB cells best around 500 nm, thus accounting for the double-minimum behavioral wavelength discrimination curve. 5. Saturation discrimination. Each opponent cell discriminates purity difference in certain spectral regions. The + R − G and + B − y cells are the most sensitive and the + Y− B least, thus accounting for the desaturation of the spectrum around 570 nm. 6. Simultaneous contrast and contours. Border enhancement is seen to luminance but not to pure color borders. The simultaneous contrast found in LGN cells extends only over very short distances, and thus cannot account for all perceptual contrast effects.