Norman J L, Pettigrew J D, Daniels J D
Science. 1977 Oct 14;198(4313):202-4. doi: 10.1126/science.905824.
Lateral geniculate nucleus cells of the kitten were classified as X-cells or Y-cells with a contrast reversal test and their latencies to optic chiasm shock were measured. X-cells with mature latencies were found as early as 21 days. Y-cells did not have adult latencies at 40 days. The early development of some X-cells may be due to differential rates of fiber myelination and synaptic maturation within the lateral geniculate nucleus.