[Studies on the spine density in lamina V pyramidal cells of the visual cortex in young and subadult rats after dark-rearing and destruction of the dorsal nucleus in the lateral geniculate body].

1. Dark reared 50 days old rats have a significantly diminuished number of spines at the apical dendrite of the lamina-V-pyramidal cells in the visual cortex. 2. Likewise we could ascertain a significant diminution of spines after destroying the upsilateral Cgld. The topistical distribution of spine density differs in both investigated series. 3. The spine diminution at the apical dendrites of lamina-V-pyramidal cells differs in this way: pyramidal cells with thick apical dendrites show a weaker spine diminution than the pyramidal cells with thin apical dendrites. 4. Some topistical problems concerning specific afferents in the visual cortex are discussed.