LIFE-SPAN DENDRITIC AND SPINE CHANGES IN AREA-10 AND AREA-18 OF HUMANCORTEX - A QUANTITATIVE GOLGI-STUDY

Dendritic neuropil is a sensitive indicator of the aging process and m ay exhibit regional cortical variations. The present study examined re gional differences and age-related changes in the basilar dendrites/sp ines of supragranular pyramidal cells in human prefrontal (area 10) an d secondary occipital (area 18) cortices. Tissue was obtained from the left hemisphere of 26 neurologically normal individuals ranging in ag e from 14 to 106 years (M-age = 57 +/- 22 years; 13 males, 13 females) . In tissue prepared by a modified rapid Golgi technique, ten neurons were sampled from each cortical region (N = 520) and were evaluated ac cording to the following parameters: total dendritic length, mean segm ent length, dendritic segment count, dendritic spine number, and dendr itic spine density. The effects of age and Brodmann areas were analyze d with a nested multiple analysis of variance design. Despite consider able interindividual variation, several clear findings emerged: 1) Den dritic systems were significantly larger in area 10 than in area 18 ac ross the sampled life span, presumably because of the more integrative function of area 10 neurons. 2) There was a significant age effect, w ith a substantial decline in dendritic neuropil from the younger (less than or equal to 50 years) group to the older (>50 years) group, espe cially in spine measures, which decreased almost 50%. 3) Dendritic val ues were relatively stable after 40 years of age, suggesting that dend ritic/spine degeneration in older, relatively healthy individuals may not be an inevitable consequence of the aging process. These findings underscore the importance of life-long commitment to a cognitively inv igorating environment. (C) 1997 Wiley-Liss, Inc.