dACC Dysfunction During Inhibitory But Not Excitatory Motor Control in OCD: Glutamate Dysmodulation Estimated using ¹H fMRS

Loss of the E/I balance of the dACC in OCD was assessed using a combination of a) motor control tasks with distinct excitatory and inhibitory modes of responding, and b) ¹H fMRS to quantify evoked glutamate changes. Basal (task-independent) glutamate levels were comparable to healthy controls, as were levels during excitatory modes of responding. However, the inhibitory mode of responding induced a specific deficit in the degree of dACC glutamate modulation in OCD patients. In surmounting shortcomings of fMRI, ¹H fMRS successfully identified loss of excitation in the E/I balance of the dACC during specific phases of motor control.