Responses of cat striate neurons to moving light and dark bars: changes with eccentricity

Responses of area-17 neurons to light and dark bars moving over a wide range of speeds were measured over a range of receptive-field locations in anesthetized and paralyzed cats. For both light bars and dark bars, velocity sensitivity shifted to higher speeds with increasing eccentricity, whereas response strength and direction selectivity hardly changed. The good correlation between response strength and velocity sensitivity for light and dark bars suggests that ON and OFF inputs converge upon most area-17 cells. The correlation between direction selectivities for light and dark bars was not better than that between velocity sensitivities for light and dark bars. Only cells with strong direction selectivity were equally direction selective for light bars and dark bars. Comparison with previous studies done with high-contrast stimuli shows that the shift in sensitivity to higher speeds with increasing eccentricity is contrast dependent.