Regional dendritic variation in neonatal human cortex: a quantitative Golgi study.

The present study quantitatively compared the basilar dendritic/spine systems of lamina V pyramidal neurons across four hierarchically arranged regions of neonatal human neocortex. Tissue blocks were removed from four Brodmann's areas (BAs) in the left hemisphere of four neurologically normal neonates (mean age=41+/- 40 days): primary (BA4 and BA3-1-2), unimodal (BA18), and supramodal cortices (BA10). Tissue was stained with a modified rapid Golgi technique. Ten cells per region (N=160) were quantified. Despite the small sample size, significant differences in dendritic/spine extent obtained across cortical regions. Most apparent were substantial differences between BA4 and BA10: total dendritic length was 52% greater in BA4 than BA10, and dendritic spine number was 67% greater in BA4 than BA10. Neonatal patterns were compared to adult patterns, revealing that the relative regional pattern of dendritic complexity in the neonate was roughly the inverse of that established in the adult, with BA10 rather than BA4 being the most complex area in the adult. Overall, regional dendritic patterns suggest that the developmental time course of basilar dendritic systems is heterochronous and is more protracted for supramodal BA10 than for primary or unimodal regions (BA4, BA3-1-2, BA18).