Do Y geniculate neurons have greater contrast sensitivity than X geniculate neurons at all visual field locations?

Contrast sensitivities for gratings of different spatial frequencies drifting at 5.2 Hz were measured for X- and Y-type neurons of the cat's dorsal lateral geniculate nucleus. It was found that, for cells with neighboring receptive fields, the peak contrast sensitivities of Y-type cells were always greater than those of X-type cells. This greater contrast sensitivity of Y geniculate cells was found not to depend on the area of visual field in which the cells' receptive fields were located.