GABA Levels Are Significantly Reduced in the Visual, Motor, and Auditory Cortex of Patients with Mild Cognitive Impairment.

One factor that might contribute to functional deterioration in patients with mild cognitive impairment (pwMCI) is a reduction in the brain's major inhibitory neurotransmitter, gamma-aminobutyric acid (GABA). Previous studies have reported reductions in GABA in pwMCI while others have not. Here we use magnetic resonance spectroscopy (MRS) to estimate GABA + macromolecules due to co-editing (GABA+) levels in six different brain regions in 37 pwMCI and 163 healthy controls. We estimate GABA+ levels using both creatine and water as reference molecules, and we analyze the effect of correcting for grey matter volume. When referenced to water, we found that GABA+ was significantly lower in pwMCI compared to controls in all six regions, even after tissue composition correction. When referenced to creatine, all but two regions exhibited lower amounts of GABA+ for pwMCI, even after controlling for tissue composition. Results suggest that pwMCI experience reductions in GABA+ throughout the brain, even in regions not typically associated with cognitive impairment.