NEURONAL SUBTYPES AND ANATOMIC ASYMMETRY - CHANGES IN NEURONAL NUMBERAND CELL-PACKING DENSITY

The combined volume of an asymmetric cytoarchitectonic area is smaller than that of symmetric homologs. Asymmetry reflects fewer numbers of neurons in the smaller of the two sides. In this study we examined two types of neurons to check whether lateral differences in neuronal num bers affect different types of neurons comparably in the neocortex of the rat. As with overall neuronal numbers, both parvalbumin-immunoreac tive (mostly long projection) neurons, and vasoactive intestinal pepti de-immunoreactive interneurons increase in number in the larger of the two sides. Moreover, the concentration of parvalbumin- but not vasoac tive intestinal peptide-immunoreactive neurons also increases on the l arger side. Thus, there may be qualitative as well as quantitative dif ferences in the connectivity of the larger side of an asymmetric archi tectonic region.