Abstract
The present study quantitatively examines age-related dendritic/spine changes in human prefrontal (area 10) and occipital (area 18) cortices. Tissue was removed from the left hemisphere of 10 neurologically normal subjects, ranging in age from 23 to 81 years. These individuals were grouped into a younger (<50 years) and older (>50 years) age group for subsequent analyses. After staining with a modified rapid Golgi technique, the basilar dendritic systems of 10 supragranular pyramidal cells per tissue block (N=200) were quantified on a Neurolucida system (Microbrightfield, Inc.). Dependent measures were total dendritic length (TDL), mean dendritic length (MDL), dendritic segment count (DSC), dendritic spine number (DSN), and dendritic spine density (DSD).
With the exception of DSC, all dependent measures tended to decrease with age. Most pronounced were significant declines of approximately 50% in DSN (F (1,2) = 118.15, p < 0.0001) and DSD (F (1,2) = 210.12, p < 0.0001) from the younger to the older age group. Dendritic differences in Brodmann's areas tended to be greater in the younger group than in the older group, with area 10 exhibiting higher dependent values than area 18, especially for DSN (F (2,36) = 11.11, p < 0.0001) and DSC (F (2,36) = 6.81, p < 0.0015). Across the represented adult lifespan, dendritic declines were slightly more pronounced in area 10 than in area 18. The present results quantitatively document the ongoing, dynamic refinement of dendritic neuropil across the human life span, and suggest that higher order cortical areas (e.g., area 10) may be more susceptible to age-related changes than lower order cortical areas (e.g., area 18). (Tissue generously provided by Dr. D. Bowerman, El Paso County Coroner, and Dr. R. Sherwin, Penrose Hospital)