Revisiting Christfried Jakob’s concept of the dual onto-phylogenetic origin and ubiquitous function of the cerebral cortex: a century of progress

This paper revisits a concept combining the evolution, ontogeny and histophysiology of the cerebral cortex, presented, in a quest to explain cognition and behavior, by the neurobiologist Christfried Jakob (1866–1956) at the Second Annual Meeting of the International Society for Medical Psychology and Psychotherapy, organized by Oskar Vogt (1870–1959) in Munich in 1911. Jakob suggested a dual onto-phylogenetic origin and a ubiquitous cortical function, claiming that most receptive pathways end up in an ‘outer fundamental layer’, which derives from the rhinencephalic apparatus, whereas the ‘inner fundamental layer’ contains effector elements and derives from the striatum. With advancing evolution, the two fundamental layers become intermingled. By attributing a functional homogeneity to the cortex, Jakob contradicted the theories of Flechsig and Cajal on ‘association’ and ‘mnemonic’ areas. The merit of Jakob’s concept rests, a century later, with the current resurgence of biological research at the evolutionary–developmental interface and the broadening anticipated from the re-integration of these two fields, especially by adding a functional dimension to the morphological traits.