Prenatal and Perinatal Development of Radial Cell Columns in the Human Auditory Cortex

Abstract

The aim of this study was to analyse cytoarchitectonic development of radial cell columns in the human auditory cortex and to correlate these ‘ontogenetic’ cell columns with the ‘adult’ pattern of radial cell arrangement. For this cytoarchitectonic analysis, brains were obtained from human fetuses and infants ranging between 9 weeks of gestation and third postnatal month. Plastic and celloidin sections containing prospective auditory areas TC, TB and TA of Economo & Koskinas were stained by Nissl method. In youngest fetuses (8–13 weeks) radially oriented cell columns (1–3 cell wide ‘ontogenetic’ columns) were found in the whole thickness of the developing cortical plate. During the next developmental stage (13–26 weeks of gestation), radial cell columns were present in the superficial part of the cortical plate, while the deep part of the cortical plate showed a variable cell arrangement due to the formation of the subplate layer (13–15 weeks), The appearance of the pale bands, and development of the prospective granular layer (18–26 weeks). After 28 weeks, parallel to the intensive areal cytoarchitectonic differentiation and ingrowth of callosal afferents, there was a gradual regional rearrangement in the ontogenetic pattern of vertical cell columnation. In the area supratemporalis granulosa (TC), radial columnation was observed as increased granularity and the appearance of short cords composed of drop-like cells. In the area supratemporalis simplex (TB) there was a progressive differentiation of elongated cell columns, intervening fibrillar stripes with appearance of pyramidal cell cords in layers III (‘organ pipe’ formations). Thus there may be a direct developmental continuation between ‘ontogenetic’ radial columns and characteristic ‘adult’ cell columns known as ‘organ pipe’ formations.