Figure 9.

The chrono-architectonic hypothesis of cortico-pontine circuit development. During development, PN neurons settle in the PN in a shell-like fashion according to their birthdate. Early born neurons form the central core of the PN, later born neurons consecutively settle around the earlier born neurons forming concentric rings (Altman and Bayer, 1987d). Similarly, it has been suggested that collaterals of the corticospinal axons innervate the PN topographically at early postnatal stages in a shell-like fashion (Leergaard et al., 1995). This suggests that the birthdate of PN neurons can be linked to both nucleogenesis and spatial organization of cortical inputs (Altman and Bayer, 1997). Consequently, intrinsic differences in PN neurons born at different stages could have an instructive role for patterning the architecture of the PN as well as their innervation. PN: pontine nuclei. (Adapted with permission from Leergaard et al., 2000, Wiley).