Cortical depth changes in enriched and isolated mice.

The occipital cortical depth was determined in laboratory mice at both 14 and 20 days of age and after various periods of postweaning exposure to enrichment or isolation. The depth was found to be maximal at 20 days of age. It declined thereafter, irrespective of environment, but the isolate cortical depth decreased faster than the enriched. The postweaning depth of the occipital cortex appears to be determined by an inevitable age-related decrease whose rate of decline may be attenuated by sensory stimulation. The postweaning cortical depth may reflect the extent of cortical neuronal development and associated metabolic activity.