Table 1.
Differences between Developing Human and Mouse Neocortex
| Quantitative Differences* | Qualitative Differences |
|---|---|
| • Number of neurons and surface area ~1000 × larger | • Introduction of new genes, gene variants, regulatory elements, and expression patterns |
| • Number or ontogenetic (radial) columns ~1000× higher | • Introduction of new neuronal types (e.g. Predecessors, VEN -Spindle cells; ISN) |
| • Length of cell cycle length (~ 3- 4 × longer) | • Distinct upper stratum of the outer subventricular zone (OSVZ) |
| • Duration of cortical neurogenesis ~ 20 × longer | |
| • Subplate Zone occupies several-fold larger portion of the embryonic cerebral wall | • Subset of GABAergic interneurons originate from the dorsal VZ/SVZ |
| • Configuration gyrencephalic rather than lissencephalic | • Neuronal migration to thalamus from the GE absent in all examined mammals (CGT) |
| • Birth occurs during later stages of cortical development | • Transient Subpial Granular Layer (SGL, absent in rodents and carnivores) |
| • Lower density of neurons, larger neuropil, higher dendritic and axonal branching | • Distinct Radial Glial Cells (early GFAP+ and differentiated and genetically distinct) |
| • Modification of common cytoarchitectonic areas (e.g. layer IV in A17) | |
| • Tempo of cortical maturation in relation to onset of reproduction very different | • Introduction of new cytoarchitectonic areas (e.g. A22, 28, 44, 45, 46) |
| • Very prolonged neoteny with cortical maturation surpassing puberty and adolescence | • Absence of neuronal turnover and resistance to regeneration |
*
The quantitative statements above are only an approximation of the level of an order of magnitude to highlight how large the differences are. The inclusion of all the references and precise numbers and measurements that may differ due to the individual variations within species as well as the methods used are not practical or appropriate in this short Perspective article.