psychology psychopathology

• Lateralisation


  The idea that the two halves of the brain are functionally different and that each hemisphere has functional specialisations
• Lateralisation


  • The left hemisphere is dominant for language
  • The right hemisphere excels at visual motor tasks
• Corpus callosum

  Nerve fibres that connect the two hemispheres and facilitate interhemispheric communication
• Split-Brain Research

  1. Sperry and Gazzaniga (1967) investigated hemispheric lateralisation

  2. Split-brain patients underwent a surgical procedure where the corpus callosum was cut

  3. Aim was to examine the extent to which the two hemispheres are specialised for certain functions
• Obsessive Compulsive Disorder (OCD)


  A disorder characterised by obsessive thoughts and compulsive behaviours
• Biological explanations for OCD

  • Genetic explanations
  • Neural explanations
• Genetic explanations for OCD

  • OCD is inherited and individuals inherit specific genes which cause OCD
  • Two genes have been linked to OCD: COMT gene and SERT gene
• COMT gene

  Associated with the production of an enzyme that regulates the neurotransmitter dopamine. One variation of the COMT gene results in higher levels of dopamine and is more common in patients with OCD
• SERT gene (5-HTT gene)

  Linked to the neurotransmitter serotonin and affects the transport of serotonin, causing lower levels which is associated with OCD (and depression)
• Neural explanations for OCD

  • Focus on neurotransmitters (serotonin and dopamine) and brain structures (basal ganglia and orbitofrontal cortex)
• Serotonin


  A neurotransmitter that regulates mood. Lower levels of serotonin are associated with mood disorders like depression and some cases of OCD
• Reduced serotonin levels


  May be caused by the SERT gene and is associated with OCD
• Anti-depressants that increase serotonin levels are effective in treating patients with OCD
• Dopamine

  A neurotransmitter. Higher levels of dopamine are associated with some of the symptoms of OCD, particularly compulsive behaviours
• Brain regions implicated in OCD

  • Basal ganglia (involved in coordination of movement)
  • Orbitofrontal cortex (converts sensory information into thoughts and actions)
• Patients with head injuries to the basal ganglia often develop OCD-like symptoms
• Disconnecting the basal ganglia from the frontal cortex during surgery reduces OCD-like symptoms
• PET scans show higher activity in the orbitofrontal cortex in patients with OCD
• Heightened activity in the orbitofrontal cortex

  Increases the conversion of sensory information to actions (behaviours) which results in compulsions, and prevents patients from stopping their behaviours
• Strengths of the biological explanation of OCD

  • Family studies show genetic link, with 37% of OCD patients having parents with the disorder and 21% having siblings with it
  • Twin studies show a strong genetic component, with 68% of identical twins and 31% of non-identical twins experiencing OCD
• Anti-depressants that increase serotonin levels are effective in reducing OCD symptoms, supporting the neural explanation
• No twin study has found a 100% concordance rate in identical twins, meaning biological factors are not the only contributor to OCD and environmental factors also play a role
• The biological explanation is reductionist and ignores other factors like cognitions and learning
• OCD may be learnt through classical and operant conditioning, where a stimulus is associated with anxiety and compulsions are negatively reinforced
• OCD (and depression)


  Result of low levels of serotonin in the brain
• SSRIs (selective serotonin re-uptake inhibitors)


  One type of anti-depressant drug, which include drugs like Prozac
• How SSRIs work


  1. Serotonin released from pre-synaptic cell into synapse

  2. Serotonin travels to receptor sites on post-synaptic neuron

  3. Serotonin not absorbed into post-synaptic neuron is reabsorbed into pre-synaptic neuron

  4. SSRIs prevent serotonin from being reabsorbed into pre-synaptic neuron

  5. Increases level of serotonin in synapse

  6. Results in more serotonin being received by post-synaptic neuron
• Anti-depressants (like anti-anxiety drugs)

  Improve mood and reduce anxiety experienced by patients with OCD
• Benzodiazepines (BZs)


  A range of anti-anxiety drugs, which include trade names like Valium and Diazepam
• How BZs work


  • Enhance the action of the neurotransmitter GABA (gamma-aminobutyric acid)
  • GABA tells neurons in the brain to 'slow down' and 'stop firing'
  • Around 40% of the neurons in the brain respond to GABA
  • BZs have a general quietening influence on the brain and consequently reduce anxiety
• Strength of biological treatments for OCD

  • Research support using randomised drug trials
  • Comparing effectiveness of SSRIs and placebos
• Soomro et al. (2008) found SSRIs were more effective than placebos in the treatment of OCD, in 17 different trials
• Another strength of biological treatments

  • Cost effective in comparison to psychological treatments like CBT
  • Doctors prefer use of drugs over psychological treatments due to cost effectiveness
• Advantage of drugs over psychological treatments

  • Non-disruptive and can be taken until symptoms subside
  • More successful for patients lacking motivation to complete psychological treatments
• Weakness of drug treatments for OCD

  • Possible side effects like indigestion, hallucinations, erection problems, raised blood pressure
  • BZs are highly addictive and can cause increased aggression and long-term memory impairments
  • Side effects diminish effectiveness as patients may stop taking medication
• Drug treatments are criticised for treating the symptoms and not the cause of OCD
• Patients prone to relapse once they stop taking drugs, suggesting psychological treatments may be more effective as a long-term solution
• Cognitive Behavioural Therapy (CBT)


  Involves both cognitive and behavioural elements
• Cognitive element of CBT


  Aims to identify irrational and negative thoughts, which lead to depression, and replace them with more positive ones
• Behavioural element of CBT


  Encourages patients to test their beliefs through behavioural experiments and homework