The responses of cells in macaque lateral geniculate nucleus to sinusoidal gratings.

Abstract

Responses of cells in the parvocellular (pcl) and magnocellular (mcl) layers of the macaque lateral geniculate nucleus to sine-wave gratings were studied. Both pcl and mcl cells responded best to a temporal frequency (drift rate) of 10-20 Hz. Pcl cells responded to temporal frequencies < 1 Hz; mcl cells did not. With colored- or white-black luminance-modulated gratings, responses of mcl cells were weaker at low than at medium spatial frequencies. With colored gratings, pcl cell responses were not attenuated at low spatial frequencies. With white gratings a few pcl cells did show such attenuation. Optimal responses from pcl cells were obtained with colored gratings; white gratings evoked weaker responses. With a grating of a color causing suppression of a pcl cell''s activity, the modulation of firing was much less than with a grating of a color excitatory for the cell. Mcl on- and off-center cells responded equally well to moving gratings. The ability of pcl cells to resolve fine gratings was dependent on cell type as well as on the color of grating used. The ability of mcl cells to resolve fine gratings was comparable to that of pcl cells. The contrast sensitivity of mcl cells was much higher than that of pcl cells. This may account for their ability to resolve fine gratings, despite their larger center size. In comparison with luminance-modulated gratings, chromatically modulated gratings could evoke larger or smaller responses, depending on pcl cell type and the colors in the grating. Mcl cells responded poorly or not at all.