Lecture 29 - Behavioural and Clinical Aspects of Drug Dependence

Question 1

Parts of the brain particularly involved in drug dependence

Answer 1

Mesolimbic system.

Ventral temental area and nucleus accumbens projecting to the cortex

Question 2

How does heroin affect the brain?

Answer 2

Binds to opioid receptors on GABA interneurons in the ventral tegmental area. This disinhibits VTA, leading to dopamine release

Question 3

Heroin relapse rates

Answer 3

42% relapse within days of leaving detox
66% addicted 6 months after detox
48% still using after 6 years.  
12% dead.
5% in prison

Question 4

Aspects of physical dependence

Answer 4

Tolerance to drug, withdrawl

Question 5

How can drug dependence lead to anhedonia?

Answer 5

Setpoint of dopamine-releasing reward system is set lower and lower. Requires greater stimulus to release dopamine

Question 6

Evidence for conditioning aspect to drug addiction

Answer 6

Heroin addicts overly-responsive to opiate-related pictures, under-reactive to naturally-rewarding images

Question 7

Brain areas affected by drug addiction

Answer 7

Orbitofrontal cortex (role in making choices)
Anterior cingulate cortex (role in long-term goals)

Question 8

Outcomes of behavioural tests on drug addicts
1)
2)

Answer 8

1) Require more of the brain to be active to perform the same tasks as unaddicted people
2) Perform poorly on gambling tasks (always pick higher-stakes options, even though they know that they shouldn’t)

Question 9

Effects of nicotine on the brain

Answer 9

No effect on adults (apart from addiction), but can affect young female brains (greater incidence of depression)