Background
Compulsive checking, a common symptom of obsessive-compulsive disorder (OCD), has been difficult to capture experimentally. Therefore, determination of its neural basis remains challenging, despite some evidence suggesting it is linked to dysfunction of cingulo-striatal systems. This study introduces a novel experimental paradigm to measure excessive checking and its neurochemical correlates.
Methods
Thirty-one OCD and twenty-nine healthy volunteers performed a decision-making task requiring them to decide whether two perceptually similar visual representations were the same or different under a high uncertainty condition without feedback. Both groups underwent magnetic resonance spectroscopy scans at 7-Tesla on the same day. Correlations between out-of-scanner experimental measures of checking and the Glutamate/GABA ratio in the anterior cingulate cortex (ACC), supplementary motor area (SMA) and occipital cortex (OCC) were assessed. Their relationship with subjective ratings of doubt, anxiety and confidence was also investigated.
Results
OCD patients exhibited excessive and dysfunctional checking, which significantly correlated with changes in the Glutamate/GABA ratio within the ACC. No behavioral/neurochemical relationships were evident for either the SMA or OCC. Excessive checking observed in patients negatively correlated with their confidence levels and positively related to doubt, anxiety and compulsivity traits.
Conclusions
We conclude that experimental measures of excessive and dysfunctional checking in OCD, linked to increased doubt, anxiety and lack of confidence, are related to an imbalance between excitatory and inhibitory neural activity within the ACC. This study adds to our understanding of the role of this region in OCD in providing a laboratory model of the possible development of compulsive checking
