Brain imaging study reveals peculiarities in uncertainty processing in obsessive-compulsive disorder

In a new study analyzing the decision-making process of individuals with obsessive-compulsive disorder (OCD), researchers discovered that those with OCD were more cautious in their decisions, took longer to make choices, and yet were less successful in their outcomes compared to healthy participants. Utilizing functional brain imaging, the study showed that while healthy individuals had increased brain activity in regions associated with uncertainty processing, this activity was absent in those with OCD, indicating a difficulty in differentiating between high and low uncertainty.

These findings were recently published in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging.

OCD is a mental health condition that affects millions of people worldwide. It is characterized by intrusive thoughts, obsessions, and repetitive behaviors or compulsions. Despite the prevalence of this disorder, the mechanisms underlying it remain a subject of extensive research.

“I study impulsivity and compulsivity or why we make rash poorly considered disinhibited decisions or on the other hand, repeat the same mistakes,” said study author Valerie Voon, a professor of psychiatry at the University of Cambridge and distinguished professor at the Institute of Science and Technology for Brain-Inspired Intelligence at Fudan University.

“I ask how these brain processes go awry in OCD and addictions. One form of impulsivity is risk taking, where we make decisions weighing the likelihood of good or bad outcomes. My group has been studying decisions under uncertainty where choices are made when the outcomes are unpredictable as compared to predictable and certain.”

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The researchers devised a study that would reveal the nuances of decision-making in both individuals with OCD and healthy individuals, allowing them to compare and contrast the two groups. The recruited a total of 83 participants, divided into three groups: OCD control participants, OCD patients treated with capsulotomy (a therapeutic surgical procedure), and healthy control participants.

The researchers employed a card gambling task as the foundation of their study, adapted from prior research. In this task, participants were presented with playing cards numbered from 1 to 10 and had to decide whether to bet on whether the next card would be higher or lower in value. Each decision was accompanied by monetary consequences – participants could either win ¥10, lose ¥10, or receive nothing based on their choices.

The task was carefully designed to manipulate uncertainty. Some cards had a lower outcome variance (low-uncertainty cards), while others had a higher outcome variance (high-uncertainty cards). Participants were asked to maximize their monetary gain throughout the task.

For the behavioral analysis, the researchers examined three key variables: bet rate (the choice to bet or not), reaction time (the time taken to make a decision), and winning rate (the success in making profitable decisions). These variables provided insight into how participants navigated uncertainty in their choices.

To dig even deeper, the researchers employed a sophisticated computational model known as the Hierarchical Drift Diffusion Model (HDDM). This model allowed them to estimate key parameters related to decision-making, including the threshold (the amount of evidence required for a decision) and drift rate (the speed of evidence accumulation).

Additionally, the study incorporated functional magnetic resonance imaging (fMRI) to observe brain activity during decision-making. The researchers focused on specific brain regions associated with uncertainty processing, such as the dorsal anterior cingulate cortex (dACC) and bilateral anterior insula (AI).

All three groups demonstrated the impact of uncertainty on their decisions. However, individuals with OCD exhibited a unique pattern of behavior. They were more cautious, taking longer to make choices (as indicated by slower reaction times), yet their decision-making was less successful (lower winning rates). This intriguing paradox highlighted the complexities of OCD decision-making.

The HDDM analysis revealed that under high uncertainty, participants in all groups tended to make riskier decisions. When faced with low uncertainty, however, participants with OCD exhibited a distinctive pattern, characterized by higher thresholds (indicating a need for more evidence) and slower drift rates (indicating a slower speed of evidence accumulation).

Functional brain imaging provided a window into the neural underpinnings of decision-making. In healthy individuals, specific brain regions, such as the dACC and AI, showed increased activity when processing high versus low uncertainty. This heightened brain activity was absent in individuals with OCD, suggesting impairments in their ability to differentiate between high and low uncertainty.

“Why do patients with OCD compulsively wash their hands until raw, even when by objective standards their hands are clean?” Voon told PsyPost. “One component may be related to how they process uncertainty. In OCD, the decision – to continue to wash or stop – is made when the outcomes are certain – their hands are by all standards clean. We show that OCD patients are slower to process information when the decision is more certain or predictable.”

“Critically, they show more impairments in brain regions such as the dACC and AI that distinguish between uncertainty and certainty. Even though they spend more time deliberating about the choice, their performance is poorer and they make more errors. These processes appear to be an endophenotype explaining the risk for the disorder and remain impaired even when their OCD symptoms improve through neurosurgical treatment.”

Contrary to expectations, the study found that individuals with OCD did not exhibit riskier decision-making behavior under conditions of high uncertainty.

“My group has a series of studies in OCD addressing the issue of uncertainty but which had always been mixed with other cognitive processes,” Voon said. “This is the first task where we think we are measuring specifically value-based uncertainty. When we first started, I had expected that impairments would arise at the highest uncertainty rather than the opposite when more certain.”

Cameron Carter, the editor of Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, said of the research: “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.”

While this study provides valuable insights, it’s essential to recognize its limitations. The research was cross-sectional, meaning it offers a snapshot in time. Longitudinal studies will be necessary to track changes in decision-making processes over time, especially for individuals undergoing treatment.

“Although we show this across two separate patient groups, it would be good to replicate this in larger patient numbers,” Voon told PsyPost. “We have just shown that it occurs but still need to understand why this occurs. We could also ask if this is more an issue with specific OCD subtypes and whether any other form of treatment designed to address this process might help improve symptoms.”

These findings open the door to further research aimed at developing targeted interventions and therapies that address these specific cognitive processes in OCD. By understanding the intricate workings of the OCD mind, researchers hope to create more effective treatments that alleviate the burden of this condition for those affected.

The study, “Evidence Accumulation and Neural Correlates of Uncertainty in Obsessive-Compulsive Disorder“, was authored by Yi-Jie Zhao, Yingying Zhang, Qianfeng Wang, Luis Manssuer, Hailun Cui, Qiong Ding, Bomin Sun, Wenjuan Liu, and Valerie Voon.