Neurobiology of Addiction Flashcards
Outline the criteria for dependance as stated in ICD-10.
- A strong desire to take the substance
- Difficulties in controlling substance use
- A physiological withdrawal state
- Tolerance
- Neglect of alternative pleasures
- Persistence despite evidence of harm
CAGE
Cut-down.
Annoyed.
Guilty.
Eye-opener.
What is CAGE used for?
As a screening test to help identify potential problems with addiction/dependence
What is meant by ‘incentive salience’?
Attributing ‘want’
What parts of the brain does the reward pathway involve?
- Ventral tegmental area (VTA)
- Nucleus accumbens
- Prefrontal cortex
What kind of signalling is DA activity in the mesolimbic pathway?
A motivating signal
What does DA signalling in the mesolimbic pathway do?
Incentivises behaviour.
What type of experience is DA signalling in the mesolimbic pathway involved in?
Normal pleasurable experiences
What do natural rewards elevate?
Dopamine levels
How is the pleasure pathway blocked?
By cutting the pathways or by administering dopamine antagonists
As a person becomes addicted to something, they can tolerate ______ levels, D2 receptors ________ and it takes ____ for them to be stimulated
HIGHER
DECREASE
MORE
Non- addicted controls had increased blood flow to the striatum upon winning
TRUE
What receptors are decreased by addiction?
Dopamine D2 receptors
What does tolerance to reward occur due to?
Repeated dopamine release, meaning that dopamine receptors down regulate
What is increased during abstinence from an additive substance?
Threshold for rewards
Normal experiences don’t evoke adequate reward response
Even with PROLONGED ABSTINENCE from substance abuse, there is still an increased threshold for rewards
TRUE
In relation to drug-taking, what is positive reinforcement?
Occurs in the initial stages of drug taking which are driven by reward.
In relation to drug taking, what is negative reinforcement?
How, eventually, drug taking becomes a thirst.
What does the pre-frontal cortex help to do?
Helps intention guide behaviour
What does the prefrontal cortex modulate?
The powerful effects of the reward pathway
What other roles does the prefrontal cortex play?
- Sets goals and focuses attention
- Makes sound decisions
- Keeps emotions and impulses under control to achieve long term goals
Explain how cortical maturation occurs.
Progresses in a back-to-front direction, beginning in the primary motor cortex and spreading anteriorly over the superior and inferior frontal gyri, with the prefrontal cortex developing last.
What direction does cortical maturation occur in?
Back to front
Compared to limbic (emotional) systems, when do frontal lobe areas that mediate executive functioning mature?
Later
What does dopamine release affect?
- Ability to update information within the PFC.
- Ability to select new goals.
- Ability to avoid compulsive repetition of a behaviour.
What is the affect of addictive drugs on the prefrontal cortex?
They provide a potent signal that disrupts normal dopamine-related learning in the PFC.
What is the relationship between age at which drug experimentation starts, and duration of relationship with drugs?
The earlier the age at which drug experimentation starts, the longer the relationship with drugs.
What are the hippocampus, striatum and amygdala critical in?
Acquisition, consolidation and expression of drug stimulus learning
What type of learning is the i) striatum ii) hippocampus responsible for?
i) Habit learning.
ii) Declarative learning.
What does the orbit-frontal cortex do?
Provides internal representations of the saliency of events, and assigns value to them
What is the KEY function of the orbit-frontal cortex?
MOTIVATION TO ACT
What happens to the orbit-frontal cortex when drug addicts are presented with cues?
There is increased activation of this area
What does hyperactivity of the orbit-frontal cortex correlate with?
Self-reported drug cravings, following exposure to cues
Overall changes in the OFC still stay even with abstinence
TRUE
Does addiction have a genetic component?
YES
How much of the risk of addiction is due to genetics?
40-60%
In relation to drugs, what may genetics affect?
- The way we respond to drugs metabolically
- Behavioural traits that predispose us to take drugs
- How rewarding we find drug taking
What impact do DRD2 receptor levels have on risk of addiction?
Low DRD2 receptors result in high risk
In relation to dopamine, what does acute stress trigger?
Release of dopamine in the neural reward pathway
In dependent individuals, what can a rapid increase in release of dopamine do?
Motivate drug seeking in dependant individuals
What is the effect of chronic stress on dopaminergic activity? What are the results of this?
Chronic stress leads to dampening of dopaminergic activity through down-regulation of D receptors
- this reduces sensitivity to normal rewards
- encourages exposure to highly rewarding behaviours
Overstimulation of the reward pathway leads to ____________
DESENSITISATION
- Pre frontal cortex dysfunctional in addicted people
- Pre frontal cortex puts the brakes on the reward pathway
- Pre frontal cortex matures late and is vulnerable whilst developing
TRUE
TRUE
TRUE
