Patients with obsessive-compulsive disorder demonstrated significantly increased activation of the ventral frontal cortex, a brain region critical to the experience of moral emotions, according to study results.
Ben J. Harrison, PhD, a clinical research fellow at the Melbourne Neuropsychiatry Centre, and colleagues used functional resonance imaging to examine the brain activity of 73 patients with obsessive-compulsive disorder (OCD) who were presented with hypothetical moral dilemmas. The participants, aged 19 to 58 years, were compared with a control group matched for age, sex and education level.
Participants with OCD were selected from a larger cohort and satisfied DSM-IV criteria for the disorder. The Yale-Brown Obsessive-Compulsive Scale was used to evaluate the presence and severity of participants’ OCD symptoms.
Participants were given 24 standard hypothetical moral dilemmas adapted into short vignettes, which were accompanied by artist-sketched representations of the scenarios. The dilemmas were designed to prompt participants to endorse an action that may result in the serious bodily harm of another, a situation in which utilitarian values violated moral–social standards (ie, sacrificing one to save many vs. do no harm to others). Twenty-four non-dilemmas were also created as an imaging baseline condition.
The frequency with which participants endorsed violations of moral–social standards ranged from 7% to 95%, and there were no significant differences between participants with OCD and controls in their overall tendency to endorse moral violations (mean, 24.6% vs. 25.9%, respectively). The moral dilemma vignettes led to “robust activation” of frontal and temporoparietal brain regions in both groups, according to researchers. Participants with OCD demonstrated significantly increased activation of the ventral frontal cortex, specifically in the medial orbitofrontal cortex. The left dorsolateral prefrontal cortex and left middle temporal gyrus were more robustly activated in participants with OCD, compared with the control group. Controlling for comorbid affective symptoms, Harrison and colleagues found that the brain regions remained increasingly active.
The severity of participants’ OCD predicted the magnitude of the activation of the orbitofrontal-striatal region, researchers said. Additionally, greater severity of harm/checking symptoms was linked to greater activation of the posterior temporal region, whereas the severity of sexual/religious obsessions was associated with greater activation of amygdala-paralimbic region.
Consistent with the researchers’ predictions, the moral dilemmas provoked greater activation of the ventromedial prefrontal and orbitofrontal cortex regions in patients with OCD.
“One view is that the medial orbitofrontal cortex, in particular, may influence such emotions by encoding the relative value and salience of environmental stimuli in support of complex decision making and anticipation about future outcomes,” they wrote. “The greater engagement of these regions in patients with OCD may, therefore, represent greater perceived salience of the emotive dilemma stimuli or excessive valuation of decision outcomes.”
Disclosure: The researchers report no relevant financial disclosures.