OCD: One Biological explanation Flashcards
Genetic explanation
Name two types of genes that are linked with OCD
- SERT gene (also called 5-HTT)
- COMT gene
What does the SERT gene do?
Organises transport of serotonin within the synapse.
Who did research into the SERT gene in two unrelated families with OCD?
Ozaki et al (2003) found a mutation of the SERT gene in two unrelated families.
The mutation led to a different form of the gene which produced lower levels of serotonin.
Low serotonin prevents normal transmission of mood relevant information from taking place.
What does the COMT gene do?
Regulates production of catechol-O-methyltransferase.
One allele of the COMT gene is more common in people with OCD.
This variation produces lower activity of the COMT gene and higher levels of dopamine (Tukel et al 2013)
Genetic factors may lead to abnormal neurotransmitter levels but may also lead to what?
Abnormal functioning of certain areas of the brain.
Which area of the brain does the ‘worry circuit’ involve?
Orbitofrontal cortex (OFC) - a region in the frontal lobe concerned with decision making.
A strength is that brain scans have showed a higher activity in the OFC, but who reported this?
Kwon et al (2003)
Where does the OFC send signals to about things that are worrying?
The thalamus via the striatum
What does the striatum normally do?
Suppresses minor ‘worry’ signals but when it is damaged it fails to suppress these signals and alerts the thalamus (sends signals back to the OFC which amplifies the worry).
How does serotonin affect the operation of the OFC?
Low levels of serotonin might cause the OFC and the striatum to malunction (Walker et al, 2009)
What does the caudate nucleus do?
It manages repetitive behaviours, so an over active CN increases repetitive behaviours.
The overactivity of the Caudate Nucleus is passed onto where?
The orbitofrontal cortex (OFC)
Who found differences in grey matter in the OFC in those suffering from OCD?
Menzies et al (2007)
Who also found increased activity in the OFC of OCD sufferers when they were shown objects that would bring on their symptoms?
McGuire et al
What can give us objective data about the brain differences of OCD sufferers?
Brain scans such as fMRI gives us objective data showing there are brain differences between two groups of people which increases the reliability of the data used to support the explanation.
