Lecture 2 - OCD Flashcards
What percentage of the population does OCD affect?
1-2%
What type of disorder is OCD classed as?
Anxiety disorder
What does OCD stand for?
Obsessive-compulsive disorder
What are obsessions?
Intrusive thoughts that you cannot get rid of.
What are compulsions?
Actions you feel driven to perform as a result of your obsessions.
Why do compulsions end up acting as a positive reinforcer for behaviour?
Compulsions relieve the negative affect caused by the obsessions.
(negative reinforcement)
There is a high co-morbidity between OCD and which other mental illness?
Depression
OCD is often treated with what?
Anti-depressants
How could Freud explain anxiety?
Insufficient control of the Id by the Ego.
What are Y-Bocs?
A measure used to quantify OCD symptoms. Stands for the Yale-Brown Obsessive-Compulsive Scale.
It establishes the time occupied by obsessive thoughts, time-intervals that thoughts are free from obsessions, interference that obsessions cause and their associated distress.
The higher the score, the more compulsive you are deemed to be/the worse your symptoms are.
Why does the compulsion eventually become impulsive?
The compulsion occurs so frequently that it becomes habit - sufferers end up performing the action without thought.
What is the difference between compulsive and impulsive actions?
Impulsive actions are rewarding, and performed without consideration for consequences (very ID), whereas compulsive actions are performed to relieve negative feelings - acts as a negative reinforcer.
What is the most common treatment for OCD?
SSRIs - selective serotonin reuptake inhibitors.
What is the recommended OCD treatment?
CBT
What do the basal ganglia co-ordinate?
- sequential processing
- control initiation
- switching
- modulation
- termination of serial processes
Involved in building up sequences of behaviour into meaningful, goal-directed repertoires. Also functions a bit like an evaluator.
What did Atmaca et al., (2007) find about structural differences in OCD patients?
Found significant differences in:
- overall white matter volume
- volume of the left and right thalamus
between OCD patients and controls.
What is the neurobiological mechanism of OCD?
Dysfunction in the cortico-striatal-thalamo-cortical circuit mechanism.
Input from stimuli is registered in the visual and then frontal cortex.
If salient enough, basal ganglia evaluation will occur (according to communication from the thalamus back to the cortex)
Amplitude/salience of signal will determine the pathway taken.
If direct pathway, positive feedback occurs, strengthening the signal each time it is evaluated.
If indirect pathway (activated by the less extreme stimuli), salience/strength of signal weakens each time.
In OCD, output from OFC takes direct pathway more frequently than normal, due to a lower threshold of activation. Therefore, the signal for regular stimuli becomes progressively bigger (amplitude) each time it is processed in the positive feedback loop that the CSTC has become. which may lead to over-exaggerated saliency and therefore increased anxiety/perceived threat.
What is the limitation of the neurobiological model of OCD?
- Explains the signal in terms of saliency, but not for it’s appraisal/reward.
- Doesn’t explain why one OCD group may have more direct pathway activation/why the threshold is lower.
What did Pujol et al., (2004) find about structural differences between OCD patients and controls?
Used voxel based morphology and found significant reduced gray matter volume in the orbitofrontal cortex, medial frontal gyrus and other regions of OCD patients, compared to healthy matched controls.
Damage to thalamic and pallidal regions leads to what?
Onset of compulsive symptoms.
Figee et al., 2013
A small stroke or damage to the frontal cortex leads to what?
Disappearance of/improvement in OCD symptoms.
Figee et al., 2013
What functional connectivity findings are established in OCD patients, according to results from Harrison et al., (2013)?
- greater connectivity between striatum and frontal cortex (OFC and ACC) in OCD patients compared to healthy controls.
- Y-Boc scores correlated with striatal-fronto connectivity (more severe the symptoms, the greater the over-connectivity)
Suggests overactivity in the CSTC loop.
What are the disadvantages of using questionnaires such as Y-Bocs to assess symptoms?
- Self administered
- May be anxiety-inducing for some patients (OCD)
Why is OCD classed as a compulsive, rather than impulsive disorder?
OCD patients do not engage in compulsive behaviours to feel good, they do it because it makes them feel less negative.