Decussation is used in biological contexts to describe a crossing (due to the shape of the Roman numeral for ten, an uppercase 'X' (decussis), from Latin decem 'ten', and as 'as'). In Latin anatomical terms, the form decussatio is used, e.g. decussatio pyramidum.
Similarly, the anatomical term chiasma is named after the Greek uppercase 'Χ' (chi). Whereas a decussation refers to a crossing within the central nervous system, various kinds of crossings in the peripheral nervous system are called chiasma.
Examples include:
The origin of the contralateral organization, the optic chiasm and the major decussations on the nervous system of vertebrates has been a long standing puzzle to scientists.[2] The visual map theory of Ramón y Cajal has long been popular[3][4] but has been criticized for its logical inconsistence.[5] More recently, it has been proposed that the decussations are caused by an axial twist by which the anterior head, along with the forebrain, is turned by 180° with respect to the rest of the body.[6][7]
Media related to Decussation at Wikimedia Commons
