Figure 1 –Dr Korbinian Brodmann, German Neurologist, Frontpiece of ‘Localisation in the Cerebral Cortex’, 1909, Public Domain*
Video of this Post
Dr Korbinian Brodmann was a German Neurologist who revolutionised the study of the brain by creating a brain map which was grounded in the microscopic properties of the brain. For the first time, researchers and clinicians alike had access to a detailed map of the brain which was described in relation to the large brain structures such as the grooves (sulci) and ridges (gyri). Brodmann had assembled a significant collection of anatomical specimens from many species. This enabled him to compare the brain maps of different species and this in turn helped him to better understand the human brain map. Brodmann’s description of the Retrosplenial Region is a case in point. Brodmann writes that the microscopic anatomy of the discrete areas he found were confirmed by him only after a comparison with the brain maps of other species.
An important feature of the brain maps are the eponymously named Brodmann Areas – discrete areas within the brain regions Brodmann described. These areas are distinguishable by the structures formed by the neurons when viewed under the microscope – the cornerstone of Brodmann’s analysis. Brodmann’s analysis of the human brain is confined to 21 pages in one English translation. What is noticeable about Brodmann’s analysis is the relative lack of photomicrographs to illustrate the features of the individual Brodmann Areas. Indeed for a work which has had so profound an impact, the relative brevity of the description is remarkable. Nevertheless it has proved a robust model of the brain.
Turning to the Retrosplenial Region, Brodmann’s description contains three Brodmann Areas
Brodmann Area 26: The Ectosplenial Area
Brodmann Area 29: The Granular Retrolimbic Area
Brodmann Area 30: The Agranular Retrolimbic Area
Figure 1 – Cytoarchitectonics of human brain according to Brodmann (1909), Public Domain*, The Top Diagram is the Lateral Surface of the Cortex, The Bottom Diagram is the Medial Surface
One interesting point of Brodmann’s description of the Retrosplenial Region is his reference to Figure 1. In the lower diagram, Brodmann acknowledges that the three Brodmann Areas cover a wider area than in reality in order to illustrate their relationships more easily.
Figure 2 – Three drawings by Santiago Ramon y Cajal, taken from the book “Comparative study of the sensory areas of the human cortex”, pages 314, 361, and 363, Public Domain*
Left: Nissl-stained visual cortex Middle: Nissl-stained motor cortex Right: Golgi-stained cortex
Brodmann also relates the Retrosplenial Region directly to the Corpus Callosum and the reader will benefit from considering the video illustration of the anatomy of the Corpus Callosum in the video below.
Video of the Corpus Callosum
Figure 4 – Hagmann et al, (2008), Extract from Figure 1 from Mapping the Structural Core of Human Cerebral Cortex, PLoS Biol 6(7): e159, Creative Commons 2.5 License
Brodmann writes that the there Brodmann Area correspond to the Isthmus of the Corpus Callosum. I pointed out some interesting relationships with the structures in Figure 4 in a previous post which the reader is directed to when considering these relationships.
Area 26: The Ectosplenial Area – this area has poorly developed lamination according to Brodmann. BA 26 is closely related to the posterior aspect of the Corpus Callosum according to Brodmann and lies within the Callosal Sulcus.
Area 29: The Granular Retrolimbic Area – Brodmann writes that BA29 has a well developed inner granular layer (layer IV) but a poorly developed layer III. This area forms a semicircle around BA26 and like this area lies in the Callosal Sulcus.
Area 30: The Agranular Retrolimbic Area – Brodmann writes that layers III and V are well developed while layer IV is poorly developed. This area encircles the two areas above, corresponds to the edge of the Isthmus and extends onto the anterior aspect of the Calcarine Sulcus.
Brodmann’s Localisation in the Cerebral Cortex. 1909. Translated and Edited by Laurence J Garey. Springer. 2006.
*Public Domain in those countries where the Copyright term of the life of the author (Korbinian Brodmann 1868-1918) plus the additional country specific term has lapsed from Copyright at the time of writing
An index of the TAWOP site can be found here and here. The page contains links to all of the articles in the blog in chronological order. Twitter: You can follow ‘The Amazing World of Psychiatry’ Twitter by clicking on this link. Podcast: You can listen to this post on Odiogo by clicking on this link (there may be a small delay between publishing of the blog article and the availability of the podcast). It is available for a limited period. TAWOP Channel: You can follow the TAWOP Channel on YouTube by clicking on this link. Responses: If you have any comments, you can leave them below or alternatively e-mail firstname.lastname@example.org. Disclaimer: The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor. The author is not responsible for the contents of any external sites that are linked to in this blog.