[Quantitative studies in lamina V-pyramidal neurons of the frontal brain after infantile brain damage]

Cortical pyramidal neurons (lamina V, Area 10) were investigated in brain autopsy material obtained from 8 patients with serious bodily and mental retardation, aged between 3 and 24 years. Quantitative neuromorphological estimations of the ramification degree, length and spine density of apical or basal single dendritic fields (SDF) of these neurons were carried out using the impregnation technique of GOLGI and a computer-assisted quantification method. The results were compared with related data found in the prefrontal cortex (Area 10 according to Brodmann) of patients in the same age without neuropathological or psychiatric disturbances. During the normal maturation period the development of dendritic length and spine density reflects the diminution of the relative excess of growth during the early postnatal phase. When comparing the dendritic length or spine density of a SDF in children with that of juvenile adolescents or young adults, the length is reduced by 40%, the spine density by 15%. In the brains of mentally retarded children we found the dendritic length reduced by 30% (apical) or 40% (basal), and a further elongation and ramification of the dendritic tree (especially nonramified terminal dendrites) in juvenile adolescents. However, the spine density showed a significant deficit of about 30% in children as well as in juvenile adolescents. This spine loss may be morphologically related to the symptoms of mental retardation. In these cases, the genetically controlled spine distribution pattern along the dendritic orders was not changed. The results obtained are discussed by taking into consideration data from animal experiments as well in view of the normal or disturbed neuronal development.