Effects of dark rearing on dendritic spines in layer IV of the mouse visual cortex. A quantitative electron microscopical study.

The effect of visual deprivation on dendritic spines in the visual cortex layer IV of 19 days old mice was studied with the electron microscopy. From the serial ultrathin sections of the selected dendrites bearing spines the author has calculated the volume and surface area of dendritic spines, and also the surface area of their synaptic zones. Employing statistical methods he has demonstrated that visual deprivation produced a retarded development of some dendritic spines in dark reared mice. The fact that the smallest dendritic spines cannot be seen with the light microscope while the number of such small spines is larger in the dark reared mice can well explain the apparent reduction in the number of dendritic spines in deprived animals studied in Golgi impregnated material.