Layer-specific dendritic regression of pyramidal cells with ageing in the human prefrontal cortex.

The dendritic field of pyramidal neurons in cortical layers IIIc and V of the prefrontal cortex in ageing humans was studied. The three-dimensional branching pattern of the basilar dendrites of Golgi-Cox impregnated neurons was analysed in the middle frontal gyrus (areas 9 and 46) in eight subjects between the ages of 49 and 90 years, all without a neurological or psychiatric disorder. The results revealed a significant regression of the layer V dendritic pattern with increasing age, but the layer IIIc neurons did not show any age-related changes. Together with our earlier data on the postnatal development of the same cell types in the prefrontal cortex, we hypothesize that the layer V neurons in the prefrontal cortex start to regress from the fifth decade onwards, in contrast to the layer IIIc neurons which remain stable from puberty on. We conclude that pyramidal cells in layer IIIc and V in a similar cortical region undergo a differential ageing effect.