DISTINCTIVE CHARACTERISTICS OF SUBCLASSES OF RED-GREEN P-CELLS IN LGNOF MACAQUE

We characterized the chromatic and temporal properties of a sample of 177 red-green parvocellular neurons in the LGN of Macaca nemestrina, u sing large-field stimuli modulated along different directions through a white point in color space. We examined differences among the proper ties of the four subclasses of red-green P-cells (on-and off-center, r ed and green center). The responses of off-center cells lag the stimul us more than do those of on-center cells. At low temporal frequencies, this causes the phase difference between responses of the two kinds o f cells to be considerably less than 180 deg. For isoluminant modulati ons the phases of on-and off-responses were more nearly 180 deg apart. A cell's temporal characteristics did not depend on the class of cone driving its center. Red center and green center cells have characteri stically different chromatic properties, expressed either as preferred elevations in color space, or as weights with which cells combine inp uts from L-and M-cones. Red center cells are relatively more responsiv e to achromatic modulation, and attach relatively more weight to input from the cones driving the center. Off-center cells also attach relat ively more weight than do on-center cells to input from the class of c one driving the center.