Biological Explanation Flashcards
What are the biological explanations of OCD?
Neuroanatomical
Neurochemical
What is the underlying principle of the neuroanatomical explanation?
That structural abnormalities in the central nervous system may be the cause of OCD
What areas of the brain are linked to structural abnormalities causing OCD?
OFC (orbito-frontal cortex)
Basal ganglia
Caudate nuclei
Thalamus
What does the OFC stand for?
Orbito-frontal cortex
What do the OFC, caudate nuclei and thalamus do?
Form a circuit whose function seems to be to convert sensory information into thoughts and actions
What is the basal ganglia connected to?
The OFC and ACC
What is the function of the OFC?
The part of the brain that becomes aware of a threat
When the OFC detects a threat what does it do?
Send a message to the thalamus
Once the thalamus has received a message from the OFC what does it do?
It sends the threat message back to the OFC
What is the function of the thalamus?
To direct messages to the appropriate areas of the brain
What is the function of the caudate nuclei?
The regulate messages sent between the OFC and thalamus
What happens when the thalamus receives a ‘threat’ message from the OFC?
It becomes excited and sends strong signals back
According to this theory, how do the brains of those with and without OCD differ?
Those with OCD have a faulty caudate nuclei
How does the caudate nuclei normally respond to the thalamus strong returned signals?
It will intercept them and suppress the worry signals preventing the thalamus from becoming overexcited
How does the caudate nuclei prevent the thalamus from becoming over excited?
It intercepts and suppresses the threat messages it has tried to send back to the OFC
Explain the neuroanatomical explanation (long version)…
The OFC detects a threat
It sends a message to the thalamus
The thalamus detects the message, becomes excited and then tries to send strong signals back to the OFC
The caudate nuclei which usually would suppress these signals, in turn, calming down the thalamus, is faulty so the thalamus remains excited and the signals go back to the OFC
This overwhelms the person with obsessions and compulsions
Give a example of the neuroanatomical explanation…
OFC: DANGER! DIRTY DESK!
Thalamus: OMG DO SOMETHING BEFORE WE GET SICK AMD DIE
OFC: WE NEED TO SCRUB IT WITH BLEACH HELP
Give an example of the neuroanatomical explanation in a person without OCD…
OFC: DANGER! DIRTY DESK!
Thalamus: OMG DO SOMETHING BEFORE WE GET SICK AMD DIE
Caudate nucleus: don’t worry it is just spilt water
What studies are relevant to the neuroanatomical explanation?
Coetzer
(Wise and Rapport)
Piggot et al
What were Coetzer’s findings?
Damage to the OFC/basal ganglia as a result from a head injury or illness such as a brain tumour can give rise to OCD
What do Coetzer’s findings suggest?
It implies there is a cause and effect relationship between basal ganglia damage and OCD
what were Wise and Rapport’s findings?
OCD is often co-morbid with disorders where the basal ganglia is damaged
what do Wise and Rapport’s findings suggest?
The caudate nucleus forms part of the basal ganglia so this shows the disorders may share a cause i.e damage to the basal ganglia
What is the main principle of the Neurochemical explanation?
That there is a link between OCD and insufficient levels of the neurotransmitter serotonin
What neurotransmitter is associated with OCD?
Low levels of serotonin
What is the role of serotonin?
It regulates mood, aggression, impulse, sleep, appetite ect
Where has evidence come from that low levels of serotonin are associated with OCD?
Observations that anti depressant drugs can relieve the symptoms of OCD
What is the role of anti-depressants?
They act on the serotonin systems in the brain
What is an example of an anti depressant?
SSRIs such as Prozac
How do SSRIs work?
They block re-uptake of serotonin which increases levels of serotonin in the synapse
What type of anti depressant is most effective in relieving OCD symptoms?
SSRIs
What study is relevant to the Neurochemical explanation?
Zohar et al
What is Zohar et als study relevant to?
The Neurochemical explanation
What were Zohar et als findings?
He found SSRIs were beneficial for up to 60% of OCD patients
Why can it not be concluded that low serotonin is the root cause of OCD?
Because it could be that low serotonin is a result of OCD because people are upset with their obsessions and compulsions and are restricted by them
What is the improved Neurochemical explanation?
Serotonin is also a neuromodulator, it has been suggested it has an important role in regulating other neurotransmitters e.g dopamine and GABA. It is thought disruption of serotonin could have a knock on effect resulting in OCD symptoms.
What were piggott et als findings?
Not everyone who suffered damage to the basal ganglia developed ocd
