[Structural change in neocortical pyramidal neurons in man in the 5th to 9th decade].

The structural changes of cortical pyramids during ageing are consisting in the reversion of the evolution (increasing spine-loss, dendritic atrophy). The spine-loss relates to all ranges of the apical dendrites in like manner. The spine density (number of spines/microm) is an useful parameter for quantitative description of ageing changes in neurons. The structural change of layer V-pyramids begins in several cortical areas in different dates, on an average in the middle of the 7th decade. The process of loss of dendrite spines is not specifically for ageing in sensu strictu, but the result of different damages (transneuronal degeneration according to sensory deprivation, poisons, circulatory disturbances, etc.).