No abstract

There has been little analysis of neurochemical correlates of compulsive behaviour to illuminate its underlying neural mechanisms. We use 7-Tesla proton magnetic resonance spectroscopy (1H-MRS) to assess the balance of excitatory and inhibitory neurotransmission by measuring glutamate and GABA levels in anterior cingulate cortex (ACC) and supplementary motor area (SMA) of healthy volunteers and participants with Obsessive-Compulsive Disorder (OCD). Within the SMA, trait and clinical measures of compulsive behaviour are related to glutamate levels, whereas a behavioural index of habitual control correlates with the glutamate:GABA ratio. Participants with OCD also show the latter relationship in the ACC while exhibiting elevated glutamate and lower GABA levels in that region. This study highlights SMA mechanisms of habitual control relevant to compulsive behaviour, common to the healthy sub-clinical and OCD populations. The results also demonstrate additional involvement of anterior cingulate in the balance between goal-directed and habitual responding in OCD.

No abstract

There has been relatively little analysis of possible neurochemical correlates of compulsive behavior to illuminate its underlying neural mechanisms. We utilised 7-Tesla proton magnetic resonance spectroscopy (1H-MRS) to assess the balance of excitatory and inhibitory neurotransmission by measuring glutamate and GABA levels in anterior cingulate cortex and supplementary motor area (SMA) of healthy volunteers and patients with Obsessive-Compulsive Disorder (OCD). Within the SMA, trait and clinical measures of compulsive behavior were related to glutamate levels, whereas a behavioral index of habitual control correlated with the glutamate:GABA ratio. OCD patients additionally exhibited elevated glutamate levels and glutamate:GABA ratios in anterior cingulate cortex which also correlated with habitual control. This study highlights important underlying relationships between SMA mechanisms of habitual control relevant to compulsive behavior, common to the healthy sub-clinical and OCD populations. The results also demonstrate additional involvement of anterior cingulate in the balance between goal-directed and habitual responding in OCD.