engleski

Postnatal development of apical oblique dendrites on pyramidal neurons in the human prefrontal cortex

Our previous study (Petanjek et al. 2008, Cereb Cortex 18:915-929) of large layer IIIC associative cortico-cortical pyramidal neurons (L3N) in the human prefrontal cortex showed that after almost a year-long "dormant" period, these neurons display a unique biphasic developmental pattern of dendritic growth. The second phase of significant elongation appears during the third postnatal year. Analysis of the large layer V cortico-subcortical projecting pyramidal neurons (L5N) showed continuous dendritic elongation during first two postnatal years. This is a typical developmental pattern described in the literature. Since basal and apical dendrites have different source of afferent fibers, we have been interested to see if the side branches of apical dendrites (oblique dendrites) display a similar pattern of dendritic growth. Quantitative analyses of reconstructed neurons impregnated by rapid-Golgi method showed a similar pattern of growth between oblique and basal dendrites. Oblique dendrites of L3N have intensive perinatal dendritic differentiation (up to 3m). After a "dormant" period during infancy, a second large dendritic elongation occurred around the age of 2y. In contrast, dendritic development for L5N appears in a linear pattern within infancy and do not elongate later on. The total length of oblique dendrites was around 3 times lower than the total length of basal dendrites, but the mean length of individual terminal and intermediate segments was roughly the same. We concluded that L3N have a unique pattern of dendritic elongation affecting all parts of dendritic tree, and this elongation takes place during the period of rapid cognitive development in preschool children.

associative cortex; cortico-cortical connections neurons; dendritic spines; working memory

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