Laminar distribution of tectal, parabigeminal and pretectal inputs to the primate dorsal lateral geniculate nucleus: connectional studies in Galago crassicaudatus.

We have studied the distribution of 3 extraretinal, subcortical inputs to the dorsal lateral geniculate nucleus of the prosimian primate Galago. Our connectional findings reveal that axons arising from the superior colliculus and the parabigeminal nucleus influence the W-cell system via their innervation of the two small-celled geniculate laminae (internal and external koniocellular) and the interlaminar zones; parabigeminal axons also innervate each of the 4 non-tectally innervated layers. Pretectal axons, on the other hand, distribute mainly to the parvocellular laminae and thus influence primarily the X-cell system.