The Biological Approach to OCD: Neural explanation

• OCD

  • A mental disorder characterised by 3 symptoms:
  • Obsessions (cognitive symptom)
  • Guilt and anxiety (emotional symptom)
  • Compulsions (behavioural symptom)
• Neural explanation of OCD focus

  focuses on neural and neurochemical factors that can cause OCD
• Orbitofrontal Cortex (OFC)

  • detects a worrying stimulus and selects an appropriate action to deal with the stimulus
  • Once the action has been selected, the Orbitofrontal Cortex sends signals to pass the brain that control our movements such as the motor cortex
• Basal Ganglia

  • The basal ganglia monitors the outcome of our actions
  • when a worrying stimulus has been dealt with, the basal ganglia sends inhibitory signals back to the Orbitofrontal cortex to shove down the signals relating to the worrying stimulus.
• Impaired communication

  • According to the neural explanation of OCD, people with OCD have impaired communication between the basal ganglia and the orbitofrontal cortex.
  • The signals sent from the basal ganglia to the orbitofrontal cortex are much weaker
  • so the orbitofrontal cortex is less inhibited than it should be and more hyperactive and this generates the symptoms of OCD.
• Neural explanation of OCD: Serotonin

  • Next, when the basal ganglia send signals to the orbitofrontal cortex, serotonin is released into the orbitofrontal cortex.
  • This inhibits neural activity in the orbitofrontal cortex
  • People with OCD have lower levels of serotonin so there is less inhibition of orbitofrontal neurons causing the neurons in the orbitofrontal cortex to become hyperactive.
• Max et al (1995)

  • studied a girl who developed OCD after having brain damage
  • Conducted an MRI and found that the girl had damage to her basal ganglia
  • Study suggests that structural damage to the basal ganglia can cause OCD supporting the idea that disturbed communication between the basal ganglia and the orbitofrontal cortex is the cause of OCD
• Saxena and Rauch (2002)

  • Reviewed brain imaging studies that compared the brain activity of adults who have OCD with the brain activity of adults without OCD
  • Found increased brain activity in the OFC of adults with OCD compared to adults without it.
  • Suggests that hyperactivity of the orbitofrontal cortex may cause the symptoms of OCD supporting the neural explanation of OCD.
• Limitations of the neural explanation of OCD

  • Results from brain imaging studies are inconsistent and have not always replicated
  • Aylward et al: no difference between the basal ganglia of people with OCD and people with healthy controls
  • Suggests that structural damage to the basal ganglia and hyperactivity in the OFC might not be the only causes of OCD.
• Aylward et al(1996)

  • conducted brain imaging study, using MRIs to investigate the brains of people with OCD
  • the researchers looked at the brains of people with OCD and compared them to a control group of adults without OCD
  • Found that there was no significant difference between the basal ganglia of adults with OCD and adults without OCD