Transient architectonic features in the basolateral amygdala of the human fetal brain.

The architectonical differentiation in the basolateral nuclei of the human fetal amygdala - with special reference to transient structures - was studied using series of relatively thick Nissl-stained sections. These architectonic features were correlated with the process of migration. Radial glial fibers providing the scaffold of migratory routes can reliably be marked with the aid of antivimentin. In the 5th gestational month a transient feature is conspicuous in the inferior portions of the basolateral nuclei bordering upon the ganglionic eminence (proliferative zone): columnar cell clusters, separated by cell-sparse septa, extend from the poliferative zone to the nuclei. The width of the cell columns vary considerably between the different nuclei. In vimentin immunopreparations fibers are found inside these cell columns. So they most probably reflect clustered migratory streams. Two months later, instead of this merging area between the ganglionic eminence and the amygdaloid nuclei a cell-free capsule envelopes the nuclei and clearly separates them from the ganglionic eminence. Changes in cytoarchitectonics are accompanied by a distinct rearrangement of radial glial fibers. A basket-like arrangement of the vimentin-immunoreactive fibers around the cell columns inside the cell sparse septa is found. Towards the end of pregnancy radial glial fibers gradually vanish. A comparison of Nissl and vimentin preparations reveals that transient architectonic characteristics as visible in relatively thick Nissl sections may be correlated with migrational routes.