Relay of receptive-field properties in dorsal lateral geniculate nucleus of the cat.

Abstract

THE DORSAL lateral geniculate nucleus (LGNd) of the cat is a principal relay nucleus on the direct pathway from the retina to the visual cortex, and several parameters of its organization as a relay are well established. First, relay cells of the LGNd have either on- or off-center receptive fields (16), because each relay cell receives direct excitatory drive from either on- or off-center retinal ganglion cells (6, 16). Second, retinal ganglion cells fall into two groups (X-cells and Y-cells) according to whether they sum the influences of the center and surround regions of their receptive fields linearly or nonlinearly (8). Most LGNd relay cells can be similarly classified because most receive direct excitatory drive from either X- or Y-type retinal ganglion cells (6). Third, each relay cell receives direct excitatory drive from either fast- or slow-conducting retinal afferents, and its own axon is correspondingly either fast or slow conducting (6, 36). The two latter parameters are closely correlated since Y-cells have been shown to have fast axons and X-cells, slow axons (6, 11). The on/off organization is independent of the other two parameters, however. Roth Y-cells and X-cells can have either on- or off-center fields. This report examines several features of the LGNd relay in the normal cat, extending previous concepts and establishing a spectrum of normal properties against which the properties of the LGNd in deprived cats (described in the following paper (3W can be compared. First, the separate relay in the LGNd of the X- and Y-cell activity of the retina is described. Second, several properties of X- and Y-cells of the LGNd were observed to vary con-Received for publication Decemljcr 27, 1971. 518 sistently with the eccentricity of their receptive fields. Specifically, variations in the relative frequency of X- and Y-cells, in their field diameter, and in the conduction velocity of their retinal afferents are described. Third, evidence is presented that the inhibitory mechanisms of the LGNd are less specifically organized than the direct cxci tatory relay.