Which brain regions are involved in obsessive‑compulsive disorder?

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Brain Regions Involved in Obsessive-Compulsive Disorder

OCD is mediated by parallel, partly segregated cortico-striato-thalamo-cortical (CSTC) circuits involving the orbitofrontal cortex, anterior cingulate cortex, striatum (caudate nucleus and putamen), and thalamus, with additional involvement of the amygdala, insula, and frontoparietal regions. 1

Core Circuit: The CSTC System

The fundamental pathophysiology of OCD centers on dysfunction within CSTC circuits that regulate sensorimotor, cognitive, affective, and motivational processes 1. These circuits can be conceptualized as four distinct but interconnected loops:

1. Sensorimotor CSTC Circuit

  • Components: Supplementary motor area (SMA), pre-SMA, posterior putamen
  • Function: Mediates stimulus-response-based habitual behavior
  • Role in OCD: Becomes hyperactive in later disease stages, driving compulsive rituals 1

2. Dorsal Cognitive CSTC Circuit

  • Components: Dorsolateral prefrontal cortex (DLPFC), dorsomedial prefrontal cortex, dorsal caudate nucleus
  • Function: Coordinates cognitive control, working memory, planning, and emotion regulation
  • Role in OCD: Shows decreased activation during executive function tasks 1

3. Ventral Cognitive CSTC Circuit

  • Components: Ventrolateral prefrontal cortex, inferior frontal gyrus, ventral caudate nucleus
  • Function: Response inhibition
  • Role in OCD: Impaired function contributes to inability to suppress compulsions 1

4. Ventral Motivational CSTC Circuit

  • Components: Ventromedial prefrontal cortex, orbitofrontal cortex, nucleus accumbens, amygdala
  • Function: Stimulus-outcome-based motivational behavior
  • Role in OCD: Hyperactive in early disease, driving anxiety and goal-directed behaviors 1

Specific Brain Regions and Their Dysfunction Patterns

Prefrontal Cortex Regions

  • Orbitofrontal cortex (OFC): Shows increased activation during emotional processing, particularly when exposed to disorder-relevant stimuli 1
  • Anterior cingulate cortex: Overactivated during emotional processing, involved in salience and arousal 1
  • Medial prefrontal cortex: Underactivated during cognitive control tasks 1
  • Dorsolateral prefrontal cortex: Decreased task-relevant activation during executive function 1

Striatal Structures

  • Caudate nucleus:
    • Head of caudate: Overactivated during emotional processing and habitual responding 1
    • Dorsal caudate: Hyperactivation associated with increased habit formation 1
    • Posterior caudate: Underactivated during cognitive control 1
  • Putamen:
    • Right putamen: Increased activation during emotional processing, especially prominent in medicated patients 1
    • Posterior putamen: Decreased activation during goal-directed behavior 1

Limbic System

  • Amygdala: Bilateral overactivation during emotional processing, most pronounced in unmedicated patients 1
  • Hippocampus: Increased activation during symptom provocation 1
  • Insula: Overactivated in salience and arousal networks 1

Thalamus

  • Ventral anterior thalamus: Decreased activation during motor control and goal-directed behavior 1
  • Part of the CSTC loop connecting cortical and subcortical structures 1

Additional Regions

  • Pallidum: Decreased activation in goal-directed behavior and motor control 1
  • Cerebellum: Involved in executive function and parietal connectivity 1
  • Precuneus and posterior cingulate cortex: Increased activation during self-referential processing 1
  • Temporal cortex: Middle temporal cortex shows increased activation during emotional processing 1
  • Parietal regions: Frontoparietal network alterations affect cognitive control 1

Disease Stage-Dependent Circuit Involvement

Early OCD phases: Alterations predominantly affect the dorsal cognitive, ventral cognitive, and ventral reward CSTC circuits plus the frontolimbic circuit, manifesting as anxiety, uncertainty, and impaired goal-directed behaviors 1

Later OCD phases: The sensorimotor CSTC circuit becomes increasingly involved, with persistent alterations in dorsal and ventral cognitive circuits driving habitual, compulsive behaviors 1

Clinical Implications

The pattern of brain alterations demonstrates:

  • Overactivation of networks involved in salience, arousal, and habitual responding (anterior cingulate, insula, caudate head, putamen)
  • Underactivation of regions mediating cognitive control (medial prefrontal cortex, posterior caudate)
  • Increased habitual responding with decreased goal-directed behavior capacity
  • Impaired cognitive control alongside heightened affective processing 1

Important Caveats

The exact involvement of neural circuits varies with:

  • Age and disease stage
  • Symptom characteristics (contamination vs. harm-related vs. symmetry)
  • Disease chronicity
  • Neurocognitive profile
  • Medication status (amygdala changes more prominent in unmedicated; putamen changes in medicated patients) 1

Some brain changes overlap with other psychiatric conditions, indicating these alterations may not be entirely OCD-specific but represent transdiagnostic cognitive-affective dysfunctions 1.

References

1
Guideline

obsessive-compulsive disorder.

Nature Reviews Disease Primers, 2019

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