The laminar organization of the prospective auditory cortex in the human fetus (11--13.5 weeks of gestation).

The prospective auditory cortex was analysed in human fetuses at 11--13,5 post-ovulatory weeks with Nissl, Golgi and E.M. techniques. At 11--12 weeks, marginal, cortical plate, intermediate, subventricular and ventricular layers were recognized. Post-migratory neurons with developing dendrites were seen in marginal layer, cortical plate and superficial part of the intermediate zone only. At 12--13,5 weeks the superficial part of the intermediate zone is transformed into the true cortical layer--"subplate layer"--characterized by maturing neurons with growing dendrites, fine axonal arborization and low cell density. The neuronal circuitry elements are thus present very early in the prospective auditory cortex and distributed throughout the deep cortical plate of the "subplate layer" corresponding to the synaptic territory of other areas of the human fetal cortex.