The brain is awash with neurotransmitters. Knowing which type of neurotransmitter does what and where is a pretty important thing to know. For OCD one of the key functional circuits of the brain is the cortico-striatal-thalamo-cortical (CSTC). Like the London underground the brain has really intensively functioning units that are like stations that are joined by communication tunnels. There is not one spot in the brain solely responsible for OCD symptoms.
In this interconnected circuit there are functional areas that seem to influence symptoms more than others. One of these is the anterior cingulate cortex (ACC – shown below). The bit that is of most interest is the part towards the nose/front. This is called the rostral anterior cingulate cortex (rACC).
The neurotransmitters in this area that are of interest are glutamine and glutamate. Like twins who dress alike they are hard to distinguish when using older brain scanning technology. There is now a new brain scanning technique that will separate the goats from the sheep. In this case it is the glutamine for glutimate. The gizmo shown below does the standard functional magnetic resonance imaging (fMRI) plus the newer analysis of proton magnetic resonance spectroscopy (H-MRS).
A recent study in 2015 examined glutamine and glutamate. The researchers had made three predictions; One: people with OCD would have increased rostral anterior cingulate cortex (rACC) activation during activities that invoke OCD symptoms compared with the non-OCD group. Two: People with OCD would demonstrate an elevated Gln/Glu ratio compared to people without OCD; and three: rACC activation and Gln/Glu ratio would show some kind of relationship.
The results showed that rACC did activate during the ‘OCD task’ but the glutamatergic neurotransmitters did not appear to be responsible for the rACC dysfunction. Put simply the researchers could point the finger at what area seems to cause the problem but not the exact mechanism of how it achieved.
Brennan, B.P., Tkachenko, O., Schwab, Z.J., Juelich, R.J., Ryan, E.M., Athey, A.J., Pope, H.G., Jenike, M.A., Baker, J.T., Killgore, W.D., Hudson, J.I., Jensen, J.E., & Rauch, S.L. (2015). An Examination of Rostral Anterior Cingulate Cortex Function and Neurochemistry in Obsessive–Compulsive Disorder. Neuropsychopharmacology, 40, 1866-1876.
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