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 in this Blog. Brodmann Area 23 is also known as the Posterior Cingulate Cortex and is also referred to as the brain’s awareness centre. This is however a simplified way of viewing this part of the brain which has many other functions. Here are 5 studies which tell us more about this part of the brain.
#1 Increased blood flow in depression. This Positron Emission Tomography study looked at 20 people with depression and compared them with 20 healthy controls. The people with depression hadn’t received any antidepressants (antidepressants might have affected the results). The researchers looked at blood flow in the brain and found an increase in Posterior Cingulate Cortex in both the right and left sides of the brain. This was a small study but makes a clear statement for others to test.
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
#2 The Posterior Cingulate shrinks with age but at a different rate to other parts of the Cingulate Cortex. This study investigated changes in the volume of the Cingulate Cortex through the lifespan. The researchers included 70 people in their study from 20 to 87. There were lots of interesting findings. Unsurprisingly they found that as people got older the Posterior Cingulate shrinks in volume. However they found it shrank at a different rate to other parts of the Cingulate Cortex.
#3 Severe Sleep Apnoea reduces the Alpha Wave activity seen in the Posterior Cingulate Cortex. Alpha waves occur in the 8-12 Hz bandwidth and are classically associated with the eye closure and seen typically in the Occipital Cortex. In this study, researchers localised electrical activity in the brain using a technique known as LORETA (Low Resolution Electromagnetic Tomography Imaging) to investigate Alpha Wave activity in Sleep Apnoea, a condition in which obstruction of the respiratory pathways during sleep causes episodes of oxygen depletion to the brain. The researchers found that people with severe Sleep Apnoea had less Alpha- Wave activity in the Posterior Cingulate Cortex compared to people with mild Sleep Apnoea.
#4 Blood flow to the Posterior Cingulate Cortex decreases during spontaneous musical sensations. Without hearing anything, people can sometimes imagine music in their minds – spontaneous musical sensations. The researchers in this study looked at blood flow in the brain using Single Positron Emission Computed Tomography. They found that while blood flow in some areas of the brain was increased when people had these spontaneous musical experiences, in the Posterior Cingulate Cortex the blood flow actually decreased.
#5 Brodmann Area 23 of the Posterior Cingulate Cortex can be subdivided into two areas with different cellular characteristics. In this study, the researchers undertook histological analysis and found that Brodmann Area 23 could be divided into two area with different thickness in layer IV and different sizes of neurons in layer Va.
For a great post on the Posterior Cingulate Cortex checkout the Neurocritic.
Can you think of any other great studies on the Posterior Cingulate Cortex?
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