Sheds more light into processing uncertainty in compulsive disorder

A neurological illness called obsessive-compulsive disorder (OCD) is characterised by compulsive repetitive behaviours like cleaning and checking even when there is obvious objective proof that the environment is clean, orderly, and proper.

Although the illness is sometimes misdiagnosed as a disorder of "fussiness," the ailment is actually caused by a problem with processing uncertainty. The brain bases for that abnormal processing are still unknown, though.

Now, a recent study in the Elsevier journal Biological Psychiatry: Cognitive Neuroscience and Neuroimaging employs brain imaging to take a deeper look at the mechanisms underlying uncertainty processing in OCD.

The researchers, led by Valerie Voon, PhD, from the University of Cambridge, looked at three groups of people: OCD sufferers, OCD sufferers who had undergone capsulotomy therapy, which is thought to reduce OCD-related brain activity, and healthy controls. The researchers wanted to look at processing in OCD, but they also wanted to look at how capsulotomy affected processing.

Dr Voon explained, “We used a simple card gambling task like that commonly used in drinking games. Participants faced with an open card simply bet whether they thought the next card would be higher or lower than the open card. At the extremes, with high or low open cards, certainty is high, but uncertainty was much higher with cards near the middle of the deck.”

For the functional magnetic resonance imaging (fMRI) experiments, the researchers focused on brain areas implicated in decision-making, namely the dorsal anterior cingulate cortex (dACC) and the anterior insula (AI). Participants with OCD displayed aberrant activity in this circuitry compared to healthy controls while determining certainty.

Dr Voon said, “Critically, patients with OCD showed slower decision-making, but only when the outcomes were more certain. Because these impairments appeared in both the OCD patients and those who had improved after capsulotomy surgery, that suggests this cognitive mechanism might be a core feature underlying why OCD develops, irrespective of how severe the symptoms might be.”

Dr Voon added, “The imaging data may provide a representation of how OCD patients might struggle with their symptoms. Whereas healthy individuals might be able to say, 'this is clean' and stop cleaning, people with OCD might struggle with that sense of certainty, and perhaps spend more time wondering 'is this still a bit dirty, or is this clean enough,' and clean further.”

The findings make clear that OCD is not a disorder of over-cleanliness but one of disordered brain processing of certainty.

Cameron Carter, MD, Editor of Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, said of the work, “This very interesting study provides an important new perspective on the mechanism underlying the disabling symptoms of OCD and suggests that developing new therapies targeting uncertainty processing in the disorder, as well as the neural systems underlying these processes, such as the dACC and AI, may offer new hope to those suffering from this difficult to treat and disabling disorder.”