Motivation and value influences in the relative balance of goal-directed and habitual behaviours in obsessive-compulsive disorder

Abstract

Our decisions are based on parallel and competing systems of goal-directed and habitual learning, systems which can be impaired in pathological behaviours. Here we focus on the influence of motivation and compare reward and loss outcomes in subjects with obsessive-compulsive disorder (OCD) on model-based goal-directed and model-free habitual behaviours using the two-step task. We further investigate the relationship with acquisition learning using a one-step probabilistic learning task. Forty-eight OCD subjects and 96 healthy volunteers were tested on a reward and 30 OCD subjects and 53 healthy volunteers on the loss version of the two-step task. Thirty-six OCD subjects and 72 healthy volunteers were also tested on a one-step reversal task. OCD subjects compared with healthy volunteers were less goal oriented (model-based) and more habitual (model-free) to reward outcomes with a shift towards greater model-based and lower habitual choices to loss outcomes. OCD subjects also had enhanced acquisition learning to loss outcomes on the one-step task, which correlated with goal-directed learning in the two-step task. OCD subjects had greater stay behaviours or perseveration in the one-step task irrespective of outcome. Compulsion severity was correlated with habitual learning in the reward condition. Obsession severity was correlated with greater switching after loss outcomes. In healthy volunteers, we further show that greater reward magnitudes are associated with a shift towards greater goal-directed learning further emphasizing the role of outcome salience. Our results highlight an important influence of motivation on learning processes in OCD and suggest that distinct clinical strategies based on valence may be warranted.

Figure 1

Two-step task. (a) Two-step task. (b) The graph shows w as a function of reward and loss outcome in obsessive-compulsive disorder (OCD) and healthy volunteer (HV) subjects. Group × outcome interaction: P=0.033. Error bars represent s.e.m.

Figure 2

Acquisition and reversal learning one-step task. (a) Acquisition and reversal learning one-step task. (b) The bar graph shows the number of trials to acquisition for obsessive-compulsive disorder (OCD) and healthy volunteer (HV) subjects as a function of outcome. Error bars represent s.e.m. *P=0.005. (c) The regression plot shows the relationship between trials to acquisition for the loss condition of the one-step task and w score for the loss condition of the two-step task.

Figure 3

Model-free and model-based analyses of two-step task. (a) The graph shows the separate analyses of model-based (MB) goal-directed and model-free (MF) habitual scores for reward (REW) and loss (LOSS) outcomes in obsessive-compulsive disorder (OCD) and healthy volunteer (HV) subjects. Group × outcome × learning interaction: P=0.005. *P<0.05, **P<0.01. Error bars represent s.e.m. (b) The regression plot shows the relationship between MF reward outcomes and the Yale Brown Obsessive Compulsive Scale score for compulsive symptoms.

Figure 4

Effects of chronic SSRIs. The left graph shows the effects of chronic SSRIs on the computational analysis (w) and the right graph on the behavioural analyses. *P<0.005 on post hoc analysis for SSRI+ versus SSRI−. The healthy volunteer (HV) group is included in the graphs for the purposes of comparison. Error bars represent s.e.m. MB, model-based; MF, model-free; OCD, obsessive-compulsive disorder; Rew, reward; SSRI, selective serotonin reuptake inhibitor.

Figure 5

Switching and effects of reward magnitude. The left bar graph shows the switch scores for both lose-switch (LSw) and win-switch (WSw) in the one-step task for obsessive-compulsive disorder (OCD) and healthy volunteer (HV) subjects as a function of valence. The right bar graph shows the computational analysis for the two-step task in HVs as a function of low (£1) and high (£5) reward magnitude. Error bars represent s.e.m. NEU, neutral.