Posts Tagged ‘acetylcholine’

OK, there’s not really a “coolest” part of the brain, but, some areas are pretty darn weird & wild.  Consider the cingulate cortex (shown here).  Electrical stimulation of the pACC region in humans can produce overwhelming fear – even a feeling that death is imminent – while stimulation of white matter tracts adjacent to area 25 can relieve treatment resistent depression. Activity in the MCC region is often associated – not with emotion – but with motor planning and selection of actions.  Stimulation of this area evoked the feeling of “I felt something, as though I was going to leave.” Interestingly, this region also contains a unique type of large neuron known as a von Economo cell,  found in humans and Bonobo chimpanzees, but not other primate species – leading some to speculate that this area must contribute to something that makes us uniquely human.  The PCC and RSC regions seem to be involved in how your brain computes where you are in 3-dimensional space, since activity in the PCC rises when participants mentally navigate pathways and routes of travel or assess the “self-relevance” of sensory stimuli, while lesions in RSC lead to topographic disorientation.  Whew, that’s a lot of functionality !  Indeed, with so many functions, its not surprising that this region is often linked to mental illness of all sorts.  In schizophrenia, for example, patients have difficulty controlling their actions (MCC regions have been implicated) as well as their emotions (ACC regions have been implicated) and maintaining a coherent sense of “self” (PCC & RSC regions have also been implicated).

Since we know that this brain region is implicated in mental illness and we know that mental illness arises – in part – due to genetic risk, it is of interest to begin to understand how genetic factors might relate to the development of structure, connectivity and function of the 4 sub-regions of the cingulate cortex.  With this in mind, it was great to see a recent paper from Brent Vogt and colleagues at the Cingulum Neurosciences Institute [doi: 10.1002/hbm.20667] which has begun to examine differential gene expression in these 4 subregions !  They examined the expression of an array of neurotransmitter receptors (at the protein level actually) and asked whether the expression of the receptors was able to differentiate (as lesions, activity and architectonics do) the 4 subregions.  In a word – yes – with the ACC region showing highest AMPA receptor expression and lowest GABA-A receptor expression.  This was very different from the MCC region which had the lowest AMPA receptor expression while PCC had the highest cholinergic M1 receptor expression.

This seems a great foundation for future studies that will continue to dissect the many interconnected – yet separable – functions of the cingulate cortex.  The “holy grail” of which might be to understand the evolutionary origins of the von Economo cells which are unique to our human lineage.  The genome encodes the story – we just need to learn to read it aloud.

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