Explanation

• What is the core assumption for biological explanations to OCD?


  It is genetic
• What are the two competing explanations for the onset of OCD?

  Candidate genes or a polygenic condition
• What are candidate genes?


  A particular gene attributing to a specific condition; received from parents
• What is a polygenic condition?


  Involvement of several genes; in OCD, gene 9 is inherited
• What do family studies indicate about the onset of OCD in the degree of relatives?

  Higher percentage of first degree relatives have OCD, 10% compared to the prevalence rate of 2%
• What did Taylor (2013) find about OCD?


  230 genes involved in the onset of OCD; different genetic variations contribute to different types of OCD
• What is the COMT gene?

  Regulates the neurotransmitter dopamine, where one variation results in higher levels of dopamine in OCD patients
• What is the SERT gene?

  Encodes the serotonin transporter protein, causing lower levels of serotonin to be active in the brain - associated with OCD
• What is the neural explanation to OCD?


  Dysfunction of neurotransmitters and brain structures
• What two neurotransmitters regulate mood?

  Serotonin and dopamine
• What is the cause of lower levels of serotonin, as associated in OCD?

  An atypical firing rate at the postsynaptic neuron
• What does higher levels of dopamine lead to?

  Compulsive behaviours
• What brain structures in the frontal lobe have an abnormal brain circuit as associated with OCD?

  Basal ganglia and orbitofrontal cortex
• What is the basal ganglia?


  Cluster of neurone at the base of the forebrain; involved in processes such as coordination of movement
• What can head injuries to the basal ganglia lead to?

  OCD-like symptoms
• What is the orbitofrontal cortex?

  Region that converts sensory information into thoughts and actions
• What do PET scans of OCD patients in the orbitofrontal cortex show?

  Higher activity; increased conversion of sensory information to actions - resulting in compulsions