Week 3- Neurobiology of addiction and alcohol misuse Flashcards
Describe the ICD-10 criteria of dependence?
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
What acronym is used for diagnosing addiction? What does it mean?
CAGE
C- cut down- have you ever felt you should cut down your drinking/whatever?
A- annoyed-have people annoyed you by criticising your drinking?
G- guilty-have you ever felt guilty about your drinking?
E-eye opener-have you ever had an eye opener (e.g. a drink in the morning to get you to wake up)
When you experience a rewarding stimulus, what occurs in the brain?
Information travels from the ventral tegmental area and travels through the nucleus accumbens to the prefrontal cortex.
Which pathway is involved in normal pleasurable experiences? Which neurotransmitter is involved?
Mesolimbic pathway.
Dopamine
What effect does the mesolimbic pathway have on behaviour?
A motivating signal and it incentivises behaviour (gives you incentive to do it).
Can you develop a tolerance to reward?
Yes- proven by gambling addicts vs non-gambling addicts
Non-gambling addicts received more blood flow to the striatum when they won than gambling addicts showing a build up of tolerance.
what happens to dopamine receptors in the brain during addiction?
Dopamine D2 receptors decrease during addiction. This is due to repeated dopamine release causing them to down-regulate.
What is positive reinforcement and negative reinforcement?
In the initial stages of taking the drug- you feel great- positively reinforcing the decision you’ve made.
However after the initial stages have worn off, you feel pretty crap and you need the drug again- negative reinforcement.
What is the role of the prefrontal cortex in addiction?
Helps intention guide behaviour
Modulates the effects of the reward pathway
Sets goals and focuses attention
Makes sound decisions
Keeps emotions and impulses under control to achieve long term goals.
How does the cortex mature?
Cortical maturation occurs in a back to front direction- starting in the primary motor cortex and then working its way to the prefrontal cortex.
Frontal lobe areas that mediate executive functioning mature later than limbic (emotional) systems.
What does dopamine release effect in the prefrontal cortex?
The ability to update information in the PFC
Ability to set new goals
Ability to avoid compulsive repetition of a behaviour.
The earlier the age the drug experimentation starts, the longer the relationship with drugs. True or false?
True.
What is the striatums role in addiction?
Habit-learning
What is the hippocampus’s role in addiction?
Declarative learning
What does the orbitofrontal cortex do?
Decides the importance of events and attaches a value to it. Its the key creator of motivation.
Describe the orbitofrontal cortex in addiction?
Addicts have increased activation of the orbitofrontal cortex when presented with drug cues. Hyperactivity of the OFC correlates with craving the drugs.
How can stress affect addiction?
Stress triggers dopamine pathways.
Rapid increase in these can motivate drug seeking in dependent individuals
Chronic stress can lead to dampening of dopaminergic activity through down regulation of D receptors
This reduces the sensitivity to normal rewards
Encourages exposure to highly rewarding behaviours.
SUMMARY NOTE
- Reward pathway involved in incentive salience
- Overstimulation leads to desensitization
- Pre frontal cortex puts the brakes on the reward pathway
- Pre frontal cortex matures late and is vulnerable whilst developing
- Pre frontal cortex dysfunctional in addicted people
- Hippocampus/amygdala/HPA axis also implicated in the development of addiction
