Disruption in the balance between goal-directed behavior and habit learning in obsessive-compulsive disorder

Abstract

Objective: Obsessive-compulsive disorder (OCD) is characterized by repetitive, ritualistic behaviors and thought patterns. Although patients with OCD report that these compulsive behaviors are unproductive and often senseless, they are unable to desist. This study investigated whether the urge to perform compulsive acts is mediated by a disruption in the balance between flexible, goal-directed action control and habitual behavior.

Method: A total of 21 patients with OCD and 30 healthy comparison subjects participated in a set of tasks designed to assess relative goal-directed versus habitual behavioral control. In the training stage, participants were asked to respond to different pictured stimuli in order to gain rewarding outcomes. In the subsequent (instructed) outcome devaluation test and in a novel "slips-of-action" test, the authors assessed whether participants were able to flexibly adjust their behavior to changes in the desirability of the outcomes. The authors also used a questionnaire to test explicit knowledge of the relationships between stimuli, responses, and outcomes.

Results: Patients with OCD showed no deficit in their ability to use feedback to respond appropriately to stimuli in the training stage. However, their knowledge of the outcomes of these responses was impaired relative to healthy comparison subjects, and patients were more prone to slips of action, indicating a deficit in goal-directed control and an overreliance on habits.

Conclusions: This study provides the first experimental evidence for selective impairment in flexible and goal-directed behavioral control in patients with OCD. The impairment forces patients with OCD to rely instead on habits that can be triggered by stimuli regardless of the desirability of the consequences. Goal-directed actions are supported by orbitofronto-striatal circuitry, and the study findings are thus in line with findings from research that implicate dysfunction in this circuitry in the neuropathology of OCD.

Figures

FIGURE 1.

Instrumental Learning Task Descriptiona a Panel A illustrates the three discrimination types: standard, congruent, and incongruent. Panel B illustrates the training phase. In this example from the standard discrimination, participants are presented with grapes on the outside of the box. If the incorrect (left) key is pressed, an empty box is revealed (and no points are earned). If the correct (right) key is pressed, participants are rewarded with cherries on the inside of the box (and points). Panel C illustrates the outcome devaluation test. In this example, participants are presented with two open boxes with a melon and cherries inside. The red cross (or X) superimposed on the cherries indicates that this fruit type is no longer worth any points. The correct response in this example would be to press the left key (which during training yielded the still-valuable melon outcome). Panel D illustrates the slips-of-action test. In this example, the initial instruction screen shows that the pineapple and cherries outcomes will now lead to the subtraction of points, as indicated by the red crosses. The other four outcomes are still valuable. Following the instruction screen, participants are presented with a rapid succession of the fruit stimuli (on the front door of the boxes) and are asked to press the correct keys (“Go”) when a stimulus signals the availability of a still-valuable outcome inside the box but to refrain from responding (“No-Go”) when the outcome inside the box has been devalued. In this particular example, participants should press the correct key when the apple stimulus is depicted on the front door (“Go”) but should refrain from responding to the grapes stimulus (“No-Go”).

FIGURE 2.

Response Accuracy Over the Course of Six Blocks in the Instrumental Discrimination Training for Participants in a Study of Goal-Directed Behavior and Habit Learning in Obsessive-Compulsive Disorder (OCD)a a Error bars denote standard deviations.

FIGURE 3.

Performance on the Slips-of-Action Test and the Explicit Response and Outcome Questionnaire in a Study of Goal-Directed Behavior and Habit Learning in Obsessive-Compulsive Disorder (OCD)a a The upper panel shows the percentage of responses made by the OCD and comparison groups in the slips-of-action test, and the lower panel shows the mean accuracy scores for the OCD and comparison groups on the explicit response and outcome questionnaire. Error bars denote standard deviations. b While there was no group difference in percentage response to valuable outcomes, patients with OCD responded significantly more often for outcomes that were devalued relative to comparison subjects (F=17.43, df=1, 38, p<0.001). c Groups did not differ in their knowledge of the correct responses from the training stage. Patients with OCD, however, showed significantly worse outcome knowledge relative to comparison subjects (F=14.92, df=1, 49, p<0.001).