Regressive Events in Brain Development and Scenarios for Vertebrate Brain Evolution (Part 2 of 2)

The problems of the evolution of varying brain size, the specialization of particular functional systems and overall differences in the relative complexity of brain organization are discussed in terms of alterations of regressive events in neurogenesis (cell death and axon retraction). Three scenarios for evolution, cascade reorganization, parcellation and heterochrony, are considered in light of regressive mechanisms during development.