Receptive-field properties of cells in the dorsal part of the albino rat's lateral geniculate nucleus.

Receptive-field properties of 273 relay (principal, P-) cells of the dorsal lateral geniculate nucleus (LGd) were studied in urethane-anesthetized albino rats, in an attempt to see if there is some relation between the visual property and the conduction velocity of afferent optic nerve fibers. According to properties of the receptive-field center, P-cells were classified into two types, common (89%) and uncommon (11%). The common type consists of OFF-phasic, ON-phasic, ON-tonic and ON-OFF-phasic cells, while the uncommon type includes ON-inhibited, moving-sensitive, ON-OFF-inhibited, simple-cell-like and complex-cell-like cells. The mean response latency to single optic chiasm shocks increases in the order of OFF-phasic (1.94 msec), ON-phasic (2.35 msec), ON-tonic (2.87 msec), ON-OFF-phasic cells (3.04 msec) and uncommon type (3.18 msec). The mean size of the receptive-field center in each of the four common types was smaller than that in the uncommon type; 6 degrees--7 degrees vs. 11 degrees. From responsiveness to moving light spots with speeds faster than 25 degrees--30 degrees/sec, P-cells of the common type were divided into the fast- and slow-movement-sensitive cells. The ratio of occurrences of fast- to slow-movement-sensitive cells decreases in the order of the OFF-phasic (2.7), ON-phasic (2.4), ON-tonic (1.1) and ON-OFF-phasic types (0.06). The optic chiasm latencies were shorter than 2.5 msec in most of the fast-movement-sensitive cells while the reverse was true for most of the slow-movement-sensitive cells. From these findings discussions were made to point out that the rat LGd mainly consists of Y- and W-like P-cells and that the Y/W dichotomy of P-cells approximately corresponds to the previously established fast/slow classification.