refers to an a scheme for indexing the multitude of concepts that occupy human thought and communication. The organization of the index is hierarchical. Developed to meet the needs of BrainInfo for a concept-oriented ontology of neuroscientific nomenclature, the branches most fully filled out relate to scientific concepts of neural structure and to communication about the nervous system. In principle, however, the hierarchical models is extensible to all concepts that people consider sufficiently significant to merit a name. Like the file structure of a computer operating system, it can be visualized as a directory to folders that contain other folders and individual files. Files correspond to concepts and folders correspond to models, i.e., complex concepts that are composed of simpler concepts. Universal Conceptual Index (UCI) is the name of hierarchy. Its top entry is 'All Concepts' ( Bowden-2008 ).