Von Economo, Koskinas and the Masters of Human Cortex Structure and function 100 years ago

This

is a translation of the most thorough and detailed examination of the cytoarchitectonics of the adult human cortex ever published. The original was published by [4]. As usual with scientific publications, their text starts with a thorough literature review – a critique of the human brain literature of their era, up to 1925, including names which later would be known to all students of human brain anatomy, such as Baillarger, Betz, Cajal, Flechsig, Golgi, His, Ariens Kappers, Meynert, Retzius, Elliot Smith and C and O Vogt. Von Economo and Koskinas often point out the lack of detail in Brodmann's Vergleichende Lokalisationslehre der Großhirnrinde (Comparative Localization in the Cerebral Cortex, 1909). They agreed with much (but not all) of Brodmann's tiling, but they provided significantly more detailed descriptions of area borders, variations, transitions, cellular structure, etc..The 800-page text is divided into a “general” and a “special” section. In the first, von Economo and Koskinas describe: 1) general cortex appearance and structure; 2) cell types, sizes, densities in the laminae, orientations, etc.; 3) the laminar structure of the isocortex, and its development; 4) the structure of the allocortex, and its development; 5) an overview of the laminae I-VI of the isocortex, their cytoarchitectonics and myeloarchitectonics, and their physiological functions; 6) cortical maps, ideal and real, and the relations of areas to gyri and sulci.In the “special part” of their book they present a catalogue (i.e. not to be read from cover to cover) organized by lobe, gyrus and cytoarchitectonic area. For each of their 120 areas and sub-areas they describe • macroscopic appearance • microscopic appearance • laminar thicknesses etc. • the contents and structure of the individual laminae • the area's extent, borders and (importantly) variants • historical comments, myeloarchitectonics • functional, neurophysiological considerations. Von Economo and Koskinas provide extensive data on cell sizes, cell densities, laminar thicknesses (on the caps and in the walls of gyri), etc.. (These are summarized in Tables 1 – 6 at the end of the text.) Importantly, they discuss individual variations in the cytoarchitectonics, including variability of areal border locations, transition zones between neighboring areas, etc..

Statement of significance

How is the knowledge from a century ago still relevant? In 1925 Prof. Constantin Freiherr von Economo and Dr. Georg N. Koskinas published Die Cytoarchitektonik der Hirnrinde des erwachsenen Menschen (The Cytoarchitectonics of the Adult Human Cortex). At about 800 pages, it is the most comprehensive and detailed survey of human cortical cytoarchitectonics ever published. Furthermore, the original was accompanied by a large folio of 112 40 × 40 cm photographic prints (“Plates I - CXII”) of the cellular structures of the cytoarchitectonic areas described in the text. Although Brodmann's [1] nomenclature remains by far the most frequently cited in the “modern” Anglo-Saxon world, his book actually contains only 22 pages (pp 130-150) dedicated to the human cortical map, and they contain only descriptions of his areas but no data. As mentioned in the Abstract, one of the important hallmarks of von Economo and Koskinas's book is the extensive description of individual variability in cortical cytoarchitectonics, with the easily inferred extensive variability in development and in functionality. (This variability, and its links to functionality, was described for the human auditory cortex in even finer detail by von Economo and Horn in 1930.) Much of this variability can only be detected by meticulously targeted sectioning, so it would be invisible in “standard” preparations (and in “normalized” brain maps). Overall the reader gets an overwhelming impression of the uniqueness of each human cortex, and thus of each human being.