Magnetic Resonance Spectroscopy (MRS) and Positron Emission Tomography (PET) Imaging in Obsessive-Compulsive Disorder

Cortical glutamate and GABA are related to compulsive behaviour in individuals with obsessive compulsive disorder and healthy controls

“…The bidirectional changes in Glu and GABA neurometabolites demonstrated here in the ACC of participants with OCD are an important addition to MRS findings in OCD because it sheds light on this inconsistent literature 10 , 11 . It is possible that this inconsistency has stemmed from the use, in many cases, of small sample sizes, different populations of participants with OCD (with co-morbidities such as skin-picking and depression 48 ) as well as evidence of impaired neuronal integrity (in studies finding concomitant changes in NAA 38 , 49 – 52 ) and variation in voxel placements.…”

“…Abnormally high levels of Glu within OCD have been suggested in animal models and by human genetic, pharmacological and neurochemical studies 7 – 9 . However, there have been inconsistent findings using proton magnetic resonance spectroscopy ( 1 H-MRS) to directly measure regional levels of these neurotransmitters (see Brennan et al 10 and Biria et al 11 for review). For example, one 3-Tesla (3T) 1 H-MRS study found evidence of reduced GABA in the medial prefrontal cortex of participants with OCD, suggesting an altered excitatory/inhibitory balance in that region 12 ; however, a later study found the reverse 13 .…”

Obsessive-Compulsive Disorder and Metabolic Disorders

“…Neurometabolites in OCD are commonly found in different brain regions, including the rostral anterior cingulate cortex (rACC), dorsal anterior cingulate cortex (dACC), basal ganglia, and thalamus. These neurometabolites include choline (Cho), creatine (Cr), aminobutyric acid (GABA), glutamic acid (Glu), glutamine (Gln), inositol (Ins), and N-acetyl aspartic acid (NAA) (Biria et al, 2021).…”

Neurobehavioral and neurochemical basis of compulsive behavior: A 7T magnetic resonance spectroscopy study in humans

“…Naaijen et al (2017) also found increased Glu in the anterior cingulate in children with OCD or autism spectrum disorder using a 3T scanner 34 , suggesting that these changes may occur early in life. However, the literature overall has hitherto lacked the resolution to quantify metabolites with smaller peaks such as GABA, Glu and Gln with a higher accuracy and a superior signal to noise ratio 35 . Although our hypothesis of elevated Glu in anterior cingulate in OCD was con rmed, we were surprised to nd signi cant increases in the occipital cortex (though not SMA) in this group suggesting that such changes may not be limited to frontal regions in OCD: however, there were no correlations shown for any of the behavioral measures, and so the functional signi cance of this change is unclear.…”