neural explanations

• Neural explanations for OCD


  Include biochemical causes, an imbalance of neurotransmitters (chemicals that communicate information between neurons) and a large neural structures in the brain that are made of many neurons (cells).
• Serotonin

  Low serotonin levels are thought to cause obsessive thoughts, and the low level of serotonin is likely due to it being removed to quickly from the synapse before it has been able to transmit its signal/influence the postsynaptic cell.

  Serotonin regulates mood and lower levels of serotonin are associated with OCD.
• Reuptake


  It seems this process happens to quickly in people with OCD, leading to reduced serotonin levels in the synapse.

  The SERT gene is the gene responsible for serotonin transportation in the synapse.
• Neural structures


  The 'worry circuit'. A set of brain structures including the orbitofrontal cortex (rational decision making), the basal ganglia system, especially the caudate nucleus, and the thalamus. Communication between these structures in the worry circuit appears to be overactive in people with OCD.
• Parahippocampal gyrus


  An area of cortex close to the hippocampus on the brain's underside is also linked to OCD. It is responsible for regulating and processing unpleasant emotions and has been seen to function abnormally in cases of OCD.
• Orbitofrontal cortex


  Converts sensory information into thoughts and actions. PET scans have found higher activity in the orbitofrontal cortex in patients with OCD. The heightened activity in the orbitofrontal cortex increases the conversion of sensory information to actions (behaviours) which results in compulsions. The increased activity also prevents patients from stopping their behaviours.
• Basal ganglia


  A brain structure involved in multiple processes, including the coordination of movement.

  In normal functioning, this filters out minor worries coming from the OFC, but if this area is hyperactive, even small worries get to the thalamus, which is then passed back to the OFC, forming a loop of recurring obsessive thoughts.
• + Practical application for the neural explanation of OCD


  E - Antidepressants (SSRIs) are used to treat OCD. SSRIs increase the levels of serotonin and are effective in reducing the symptoms of OCD.

  E - This shows that serotonin has an effect on the severity of symptoms as explained by the neural explanation of OCD.

  L - Therefore, this supports the explanation and has also allowed for successful treatments to be made.
• + Supporting evidence for orbitofrontal cortex and OCD from PET scans


  E - Several neuroimaging studies using PET scans have shown hyperactivity in the orbitofrontal cortex and the caudate nucleus in people with OCD both while at rest and when symptoms are stimulated.

  E - This suggests that this part of the brain is involved in OCD.

  L - However, we cannot be sure if the hyperactivity is the cause of OCD or a consequence of having OCD.