Alphabetical list

White matter ( WM ; Meckel, 1817 ) : Since the 16th century the nervous system (Monro, 1783) has been divided more and more precisely into gray matter (Meckel, 1817) and white matter based on their appearance in freshly dissected material observed with the naked eye (macroarchitecture); since the 19th century this differentiation has been made at the histological (microarchitecture) level. White matter is the nervous system compartment that consists primarily of axons (Kölliker, 1896). Its name is derived from its appearance in fresh and fixed macroscopically observed material, its whitish color due to the presence of myelinated axons. However, white matter is often a mixture of myelinated axons and unmyelinated axons, and entire aggregates of axons can be unmyelinated. Therefore, as defined here white matter is a generic term for a nervous system volume where axons are the predominant neural component, although of course glia (Virchow, 1846) and parts of the circulatory system, vascular cells, are also present. White matter can contain scattered neurons (Waldeyer, 1891) that may be assigned either to an adjacent gray matter region, or to a new gray matter region embedded (nested) within the white matter; assignment depends on differentiable neuron types (Bota & Swanson, 2007) involved. There is often a fuzzy border of variable width and difficult to measure between gray matter and white matter. This use of the term was probably introduced by Meckel; see English translation (1832, vol. 2, pp. 152-154), also see Herrick (1915, p. 108). For early history see Clarke & O'Malley (1996, Ch. 10); for modern histological interpretation see Peters et al. (1991), Swanson (2003, pp. 60-66). more details

White matter tract ( Swanson & Bota, 2010 ) : A recognizable division of white matter (Meckel, 1817) in the nervous system (Monro, 1783) that can be bordered by gray matter (Meckel, 1817), another white matter tract(s), or non-neural tissue. Borders between white matter tracts are determined by defined structural landmarks and are commonly arbitrary. White matter tracts may be homogenous or heterogeneous. A homogeneous tract only has one specific mesoconnection (Thompson & Swanson, 2010) within it, whereas a heterogeneous tract has two or more specific mesoconnections within it. The traditional way to view vertebrate white matter tracts is with a myelin stain, supplemented with a reduced silver stain (Brodal, 1981, p. 5). There are many general terms for a white matter tract; some examples include pathway, bundle, fascicle, funiculus, column, peduncle, decussation, commissure, and nerve, whereas others have specific names like corpus callosum, fornix, and internal capsule. As a complete set, white matter tracts can be arranged in various ways, for example, strictly topographically into transverse tracts, longitudinal tracts, and local tracts. White matter tracts were distinguished in the second century by Galen (c177; see translation by Singer, 1999, pp. 231, 234) for macrodissected nonhuman mammals, and were referred to as tracts as long ago as Willis (1664; see translation by Pordage, 1681, pp. 61, 91) for macrodissected adult humans and other large mammals. more details

Wiring diagram ( Swanson & Bota, 2010 ) : An illustration of the physical arrangement of connections (including route information) between a set of nodes-gray matter regions, neuron types (Bota & Swanson, 2007), or neurons (Waldeyer, 1891)-in the nervous system (Monro, 1783). Wiring diagrams can be at various levels of abstraction from three-dimensional models to two-dimensional schema but a complete wiring diagram, by definition, includes route information; see Gregory (1966), Wikipedia (Wiring diagram). more details