They wanted to determine neural correlates of excessive habit formation in OCD. OCD-patients had a hyperactivation in the caudate nucleus during the learning phase.

OCD patients exhibited excessive habits that were associated with hyperactivation in a key region implicated in the pathophysiology of OCD, the caudate nucleus. Previous studies indicate that this region is important for goal-directed behavior, suggesting that habit-forming biases in OCD may be a result of impairments in this system, rather than differences in the buildup of stimulus-response habits themselves.

Recent research into habit formation and goal-directed behavior in OCD has found that excessive habit formation may result from deficits in the goal-directed system.

Three very interesting regions:

  • Medial orbitofrontal cortex
  • Caudate nucleus
  • Putamen

Generally, the habit hypothesis of OCD exhibits good face validity in that both habits and compulsions continue in spite of awareness that these actions are not useful/wanted (i.e., ego-dystonic) and are associated with the experience of an urge to perform them (6).


Participants were instructed to avoid getting shocks for a few trials, then researchers showed to the patients how they disconnected one of the electrodes. This “outcome devaluation” was then a measure of excessive habit formation. Did the OCD patients continue avoiding shocks to the wrist that had been disconnected even though it didn’t matter anymore?


So OCD patients responded more to devalued stimuli and had higher urges. BUT! More than half (21 out of 37) in the OCD group did not show excessive habit formation.


Habits in OCD were associated with hyperactivation in the caudate nucleus. Specifically, greater caudate activity was observed in patients whose actions had become habitual, compared with healthy comparison subjects and OCD patients who did not form habits. Independent analysis revealed that, across the entire OCD group, greater activation in this region was correlated with the self-reported urge to perform these habits; there was no such relationship in healthy comparison subjects.

Hyperactivation in the caudate is one of the most consistent neurobiological markers of OCD symptoms (with medial orbitofrontal cortex hyperactivation being the other) (18, 19), and our data therefore lend strong support to a model of OCD centered on deficits in goal-directed control over actions, resulting in compulsive habits.


These data implicate dysfunction in regions that support goal-directed control over action in excessive habit formation in OCD. These data also add convergent support to the habit hypothesis of OCD, such that it exhibits excellent neurobiological convergence with the known pathophysiology of OCD.