Increases in size and myelination of the rat corpus callosum during adulthood are maintained into old age.

Although there are indications of growth in the size and myelination of the rat corpus callosum during adulthood, it is not known how long this growth continues. In addition, the potential for age-related changes in these measures to affect the sex differences seen in adulthood has not been examined. Here the size of callosal subregions and area occupied by myelin were examined in the genu and splenium of male and female rats in adulthood, middle age and old age. Our findings revealed increases both in size and in the area composed of myelin between adulthood and middle age that were maintained into old age, with no indications of age-related loss in either the genu or splenium of the rat.