Genesis of neurons in the dorsal lateral geniculate nucleus of the cat.

Neurons that will ultimately form the dorsal and ventral lateral geniculate nuclei, the medial interlaminar nucleus, the perigeniculate nucleus, and the nucleus reticularis of the cat undergo their final cell division beginning on, or slightly before, embryonic day 22 (E22) and ending on, or before, E32. Early in this period, neurogenesis proceeds for all of these geniculate nuclei, whereas only in the dorsal lateral geniculate nucleus does cell birth continue until E32. Distinct spatiotemporal gradients of cell birth are not obvious within any of the individual geniculate nuclei. For the dorsal lateral geniculate nucleus in particular, and for the other geniculate nuclei in general, neurons born early in this period exhibit a full range of adult soma sizes, including large and small neurons. Neurons born late in this period exhibit only small adult somas. The location and size of a neuron within the dorsal lateral geniculate nucleus provide clues to that cell's functional properties. On the basis of presently available information regarding the relationship between structure and function of neurons in the cat's dorsal lateral geniculate nucleus, the findings described here suggest that all functional classes of neurons in the dorsal lateral geniculate nucleus are born at the same time throughout most of this period.