Lesion of the PGO pathways in the kitten. II. Impairment of physiological and morphological maturation of the lateral geniculate nucleus.

Suppression of the geniculate ponto-geniculo-occipital (PGO) waves by bilateral lesions of PGO pathways at the mesencephalic level in 15-day-old kittens has been shown to induce a significant reduction of the mean discharge frequency recorded in the lateral geniculate nucleus (LGN) during paradoxical sleep. The present paper reports that one month after the bilateral lesion (i.e., 6-7 weeks of age) important deficits in the maturation of the LGN were observed: (1) electrophysiologically, the latencies of the LGN cellular responses to stimulation of the optic chiasm were significantly longer than those of age-paired controls or of unilaterally lesioned animals, and the proportion of visual cells characterized as type X by stimulation of the visual field was smaller; and (2) morphologically, the volume of the LGN and the size of its neuronal somata were smaller than those in control. These data suggest that bilateral suppression of extraretinal PGO afferents to the LGN in the kitten induces a significant delay in the development of this nucleus.