Fig. 2.

Top, Spatial weighting functions of an off-center magnocellular neuron (23° eccentric) measured with L-cone-isolating, M-cone-isolating, and luminance-modulated stimuli. Each panel corresponds to the same region of visual space, 5.2° on a side. On responses are coded in redand off in blue; the brighter the red orblue, the stronger the response. All maps, L- and M-cone isolating and luminance, have an off-center/on-surround organization. Individual pixels (0.43°) are outlined in black. Pixels in the center (defined as in Materials and Methods) are outlined in white. Surround is a ring of four pixels around the center. Data are smoothed by a function that falls to <10% at one-half pixel. Delay between stimulus and response, 15–30 msec. Bottom, Radial weighing functions calculated from the spatial weighting function above (see Materials and Methods). For comparison with the spatial weighting function, the radial weighing function is reflected about the origin so that each value is shown twice. To facilitate comparison, we have given all responses in units of spikes/(sec · C), whereC is the cone contrast of the stimulus (see Materials and Methods).