#2 Studies That Tell Us About A Brain Region Seldom Studied – Brodmann Area 26

The Retrosplenial Cortex, Brodmann Area 26, Derived from Gray’s Anatomy 20th Edition 1918 Lithograph Reproduction, Public Domain

The brain is a complex structure and but can be organised according to several principles. One approach is to characterise the brain regions according to the microscopic properties of these regions.  More specifically the neurons are organised differently between regions. Some regions may contain unique types of neurons. This approach to understanding the organisation of the brain was proposed by the German Neuropathologist Korbinian Brodmann and resulted in the eponymously named Brodmann Area. There are 52 areas in all and I have covered other Brodmann Areas elsewhere.

One region in particular Brodmann Area 26 (BA26) is very interesting as I could find few studies on this area. I undertook a search on Medline (via PubMed) using the search term ‘Brodmann Area 26′ and found 30 references which revealed 2 relevant studies after excluding papers which were irrelevant (e.g one abstract for instance referred to ’26 subjects’ and Brodmann Area elsewhere causing the search engine to identify this as relevant). So in the end there were 2 studies. The experienced neuroscientist might be asking why not use the Retrosplenial Cortex as a search term instead. BA26 is classed as Retrosplenial Cortex (RSC) but is a subset of the RSC and that’s where the problem is. This series is on the Brodmann Areas and how we can understand the brain by strictly adhering to these areas in answering questions about the brain. Studies that use the RSC don’t necessarily constrain their answers to BA26. As an example look at this study. Although examining the functional connectivity of the RSC, a close examination of the paper reveals that BA26 is not included within the remit of the RSC (although it does include BA29 for instance). So in summary by constraining the search to Brodmann Area 26, a limited  number of papers are identified but that is necessary given the aims of the search.

Thus two studies were identifed

#1 Triggering Traumatic Memories in People With PTSD Reduces Activation in BA26. This Positron Emission Tomography (PET) study involved people who had been exposed to trauma in recent war zones and were experiencing Post-Traumatic Stress Disorder. The researchers found that when traumatic memories were experiences through stimuli there was a reduction in blood flow to BA26. In PET studies, it is assumed that the changes in blood flow detected by the PET scan represent changes in activity in the brain. The researchers used (15)Oxygen water to investigate regional cerebral blood flow (rCBF). What the researchers also found was in increase in activity in several areas including the motor cortex which they interpreted to mean that the person was readying for motor action in response to the stressful stimulus.

#2 There are few Pyramidal Cells below the Granular Layer in BA26. The Cerebral Cortex has a highly organised structure at a microscopic level. The Cerebral Cortex is organised into six layers. Layer 2 is the Granular Layer. The Cerebral Cortex contains neurons known as Pyramidal cells. The researchers in this study found that there were few Pyramidal Cells beneath the Granular Layer.


Neuroanatomy Resources

Index: There are indices for the TAWOP site here and here 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 justinmarley17@yahoo.co.uk. 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.


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