In theory, if a single mutation popped up
that caused immature neurons to undergo just one extra cycle of cell division, that could double the final size of the cortex.
It is not yet known whether the dramatic and selective effects of the NGF antibodies are due to a direct toxic action of the antibodies on
immature sympathetic
neurons or to an inactivation by the antibodies of circulating molecules of NGF, thereby indirectly
causing the death of the sympathetic
neurons by depriving them of the NGF they need in order to survive.