SPATIAL AND TEMPORAL PROPERTIES OF X-CELLS AND Y-CELLS IN THE CAT LATERAL GENICULATE-NUCLEUS

Extracellular recordings were obtained from units in the dorsal lateral geniculate nucleus of anesthetized cats. Of 69 units, 63 could be unambiguously identified as either X (n = 33) or Y (n = 30) by testing the presence of a null response to stationary sine wave gratings presented in different spatial phases. In response to stationary gratings flashed on the off, Y cells exhibited bigger, more transient responses than X cells. All Y cells but few X cells exhibited a shift effect (modulated periphery effect). In response to drifting sine wave gratings of different spatial frequencies, X cells preferred higher spatial frequencies and showed smaller peak contrast sensitivities and somewhat narrower tuning curves than Y cells. In response to a sine wave grating of optimal spatial frequency drifting at different velocities, X and Y cells had similar temporal tuning curves. Y cells, largely because they preferred lower spatial frequencies, preferred higher drift velocities than X cells. X and Y cells perhaps can be differentiated objectively on the basis of a number of discharge parameters. These parameters are compared with similar data collected by others from neurons in the visual cortex.