History of the Study and Nomenclature of the Claustrum

This account of the progress of research on the claustrum considers it in five consecutive historical eras. The first era, 1780 to 1820 was a time of discovery by Vicq d’Azyr of a particular and curious subdivision of the forebrain, and the initial spread of this knowledge. The second era, 1820 to 1870 saw its naming, by Burdach and others, originally with several terms but ending with agreement to call it the claustrum, and its establishment in the neuroanatomical canon. In the third era, 1870 to 1950, new staining technology introduced by Golgi, Nissl, Weigert, and Marchi, and particularly the employment of the first two, by Ramon y Cajal and by Brodmann, allowed some understanding of its distinctive structure and gross anatomical relationships. In the fourth era, 1950 to 2000, an explosion of new techniques brought information about connections and possible functions, exemplified in the work of LeVay and Sherk, delineating the visual region of the claustrum of the cat, and establishing that region as a satellite of visual regions of cerebral cortex. The fifth era, beginning in the year 2000, sees even more radical technical developments, including proteomics and astrocytic analysis, that promise, at last, significant information about what this mysterious brain structure is and does.