Modularity in vertebrate brain development and evolution.
Embryonic modularity and functional modularity are two principles of brain organization. Embryonic modules are histogenetic fields that are specified by position-dependent expression of patterning genes. Within each embryonic module, secondary and higher-level pattern formation takes places during development, finally giving rise to brain nuclei and cortical layers. Defined subsets of these structures become connected by fiber tracts to form the information-processing neural circuits, which represent the functional modules of the brain. We review evidence that a group of cell adhesion molecules, the cadherins, provides an adhesive code for both types of modularity, based on a preferentially homotypic binding mechanism. Embryonic modularity is transformed into functional modularity, in part by translating early-generated positional information into an array of adhesive cues, which regulate the binding of functional neural structures distributed across the embryonic modules. Brain modularity may provide a basis for adaptability in evolution.
Redies
C
C
Institute of Anatomy, University of Essen School of Medicine, Germany. christoph.redies@uni-essen.de
Puelles
L
L
D000818:Animals; D005075:Biological Evolution; D001921:Brain / Q000196:embryology* / Q000502:physiology; D006801:Humans; D014714:Vertebrates / Q000196:embryology