Neurobiology of addiction

Question 1

What is the main system of the brain involved in addiction

Answer 1

Mesolimbic system (Dopamine - reward pathway)

Question 2

What are the 3 main regions of the mesolimbic system?

Answer 2

Nucleus accumbent
Ventral-Tegmental area
Prefrontal cortex

Question 3

How does the mesolimbic system cause addiction?

Answer 3

Substance use causes increased dopaminergic activity in the mesolimbic pathway and acts as a reward system, therefore incentivises the behaviour

Question 4

How does alcohol affect the mesolimbic system?

Answer 4

Increases opioid release which stimulates the nucleus accumbens, causing reward sensation

Question 5

How does nicotine affect the mesolimbic system?

Answer 5

Increases dopamine release from the VTA to the NAc, causing reward sensation

Question 6

How do cannabinoids affect the mesolimbic system?

Answer 6

Increases stimulation of the NAc via the VTA

Question 7

How does PCP - Phencyclidine - Angel dust affect the mesolimbic system?

Answer 7

Directly stimulates dopamine release from the NAc

Question 8

How does repeated substance use cause tolerance?

Answer 8

Due to repeated dopamine release during substance misuse, dopamine receptors are shown to down-regulate

This increases the threshold for reward and so more is required to produce the reward

Also normal pleasurable experiences such as food or intercourse may not evoke an adequate reward response

Question 9

What is the function of the pre-frontal cortex?

Answer 9

The pre-frontal cortex helps intention to guide behaviour and modulates the powerful effects of the reward pathway

It also plays a role in setting goals and focussing attention

It allows us to make sound decisions and keeps emotions and impulses undercontrol to achieve long-term goals

Question 10

When does the pre-frontal cortex finish developing?

Answer 10

Adulthood

Question 11

How does drug abuse affect the pre-frontal cortex

Answer 11

Drug abuse has been associated with reduced pre-frontal cortex functioning

Question 12

How does early experimentation with drugs affect the brain?

Answer 12

Neurones that fire together, wire together in early age due to synaptic plasticity

This means the earlier age at which drug experimentation starts, the longer the relationship with drugs

Question 13

What are some factors that can affect the mesolimbic system, increasing risk of addiction?

Answer 13

Childhood trauma, genetic susceptibility and acute stress