Evidence Accumulation in Obsessive-Compulsive Disorder: the Role of Uncertainty and Monetary Reward on Perceptual Decision-Making Thresholds

Abstract

The compulsive behaviour underlying obsessive-compulsive disorder (OCD) may be related to abnormalities in decision-making. The inability to commit to ultimate decisions, for example, patients unable to decide whether their hands are sufficiently clean, may reflect failures in accumulating sufficient evidence before a decision. Here we investigate the process of evidence accumulation in OCD in perceptual discrimination, hypothesizing enhanced evidence accumulation relative to healthy volunteers. Twenty-eight OCD patients and thirty-five controls were tested with a low-level visual perceptual task (random-dot-motion task, RDMT) and two response conflict control tasks. Regression analysis across different motion coherence levels and Hierarchical Drift Diffusion Modelling (HDDM) were used to characterize response strategies between groups in the RDMT. Patients required more evidence under high uncertainty perceptual contexts, as indexed by longer response time and higher decision boundaries. HDDM, which defines a decision when accumulated noisy evidence reaches a decision boundary, further showed slower drift rate towards the decision boundary reflecting poorer quality of evidence entering the decision process in patients under low uncertainty. With monetary incentives emphasizing speed and penalty for slower responses, patients decreased the decision thresholds relative to controls, accumulating less evidence in low uncertainty. These findings were unrelated to visual perceptual deficits and response conflict. This study provides evidence for impaired decision-formation processes in OCD, with a differential influence of high and low uncertainty contexts on evidence accumulation (decision threshold) and on the quality of evidence gathered (drift rates). It further emphasizes that OCD patients are sensitive to monetary incentives heightening speed in the speed-accuracy tradeoff, improving evidence accumulation.

Decision-making under uncertainty in obsessive–compulsive disorder

“…Recent studies (Dar, 2004; Stern et al, 2013; Banca et al, 2014) have focused on these questions and found that OCD are less confident in their choices, and more uncertain regarding whether their actions have been performed correctly. Our goal was to derive objective behavior-based measures that may reliably characterize OCD and potentially be used in follow up studies of neurobiological impairments.…”

Doubt and the decision-making process in obsessive-compulsive disorder

“…17 In a study using the Random Dot Matrix tasks, Banca et al showed that, under conditions of high uncertainty, individuals with OCD had a delay in reaching the decision threshold, compared to healthy controls. 18 Moreover, even under conditions of low uncertainty, they had difficult acquiring information to make decisions. Of note, the patients responded to instructions, that monetary incentives could be garnered by increasing speed, with a reduction in their previously delayed reaction times.…”

Value-based decision making under uncertainty in hoarding and obsessive- compulsive disorders

“…Perceptual decision making entails accumulation of sensory information towards a categorical choice between alternatives (e.g., a melon is bigger than an apple). In studies employing a range of behavioral paradigms, those with OCD tend to act more cautiously during perceptual decision making than healthy individuals (Beads Task: Fear and Healy, 1997; Pélissier and O’Connor, 2002, Random Dot Motion task: Banca et al, 2015; but also note negative results by Jacobsen et al (2012) and Chamberlain et al (2007). In contrast, value-based decisions depend on subjective goals (e.g., I like melons more than apples) and are assumed to follow several simple and intuitive rules (Rangel et al, 2008).…”