A Theory for Innate Properties of Synaptic Wiring Diagrams in the Neocortex

Daniel Udvary1, Philipp Harth2, Vincent J. Dercksen2, Hans-Christian Hege2, Christiaan P.J. de Kock3, Bert Sakmann4, Marcel Oberlaender5 1 research center caesar 2 Zuse Institute Berlin 3 Vrije Universiteit Amsterdam 4 Max Planck Institute of Neurobiology 5 research center caeesar

Which properties of the brain’s neuronal networks are genetically encoded? Which ones represent learning and experience? Here we address these questions for the mammalian neocortex. We discover that the complex topology of neocortical networks can originate directly from genetically induced programs that guide soma, dendrite and axon distributions during development. The resultant theory predicts wiring properties that are consistent with the vast majority of empirical observations, such as the degrees of sparsity, heterogeneity and recurrence. Developmental programs that shape the neuropil hence implicitly encode intricate properties of neocortical wiring diagrams at subcellular, cellular and network levels. In contrast to simpler organisms, where genomes have the capacity to encode the complete wiring diagram explicitly, implicit encoding may represent a general feature of the mammalian neocortex that ensures robustness of its basic functionalities during remodeling by learning and experience, as well as flexibility for fast adaption to environmental changes.