Dopamine & desire: L17

Question 1

What produces and releases dopamine (2)?

Answer 1

(1) Ventral tegmental area (VTA) = motivation & emotional response, dires & addiction
(2) substantial nigra (SN) = motor control

Question 2

Dopamine synthesis

1. tryrosine
2. synthesis enzyme names (2)
3. breakdown
4. many drugs affecting the dopamine system also affect
5. dopamine b-hydroxylase is

Answer 2

1. an amino acid found in food -> small changes in structure lead to dopamine
2. tryrosine hydroxylase (amino acid -> DOPA)
   amino acid decarboxylase (DOPA -> dopamine)
3. broken down (by dopamine b-hydroxylase) and synthesised into noradrenaline
4. noradrenaline system because they are the same compound (pathways closely linked)
5. a synthesis & breakdown enzyme

Question 3

If the body doesn’t have enough tryrosine and the body isn’t producing enough dopamine then…

Answer 3

Synthetic L-dopa is administered

artificial compound then synthesised by the body into dopamine (by amino acid decarboxylase)

Question 4

Dopamine and parkinsons

1. caused by
2. initially characterised by
3. later by
4. currently (Cure)
5. treatment

Answer 4

1. death of domaine cells in substantia nigra
2. motor tremor
3. cognitive impairments and dementia, reduced executive function
4. no cure, but symptoms can be reduced through drugs and deep brain stimulation
5. can cause impulsivity, hyper sexuality, gambling and addictive like behaviours

Question 5

Reward prediction error

1. if an unexpected reward occurs
2. if reward is repeatedly given after a stimulus (beep)
3. if the reward is expected & not provided

Answer 5

1. DA neurons become more active and release a burst of DA
2. the reward will be expected and no DA will be released with the reward but will be released at the time of the beep
3. DA neurons will be suppressed

Question 6

reward

1. example
2. rewards can be

Answer 6

1. if loss or gain of money is unexpected the feelings associated with it are more intense (because we value money)
2. real (food, sex), symbolic (money), virtual (points in a game)

= DA involved in all cases

Question 7

Cognitive control and reward

1. cognitive effort linked to
2. it is proposed that DA
3. task persistence is justifiable only while
4. what helps with motivation
5. define opportunity costs
6. cognitive tasks with low success are

Answer 7

1. working memory and cognitive control
2. codes both goal rewards and effort costs and that the averse feeling of cognitive effort reflects “opportunity cost”
3. process outpaces accruing costs
4. incentives, counterbalance opportunity cost
5. everything else rewarding you could be doing with your time (e.g. watching a video)
6. particularly unpleasant and might bias someone towards disengaging and selecting the low-cost “guess” option

Question 8

Addiction & dopamine

- gambling

Answer 8

• unpredictability boosts DA
• if you predictably lost 70% of your money it wouldn’t be addictive
• if you have unexpectedly large wins (still loosing average 70%) the wins are coded as extremely positive

Question 9

Addiction & dopamine

- drugs (chronic relapsing disorder)

Answer 9

• chronic relapsing disorder consists of a compulsive pattern of drug-seeking and drug-taking behaviour
• takes places at the expense of other activities
• persists despite adverse consequences

Question 10

Addiction & dopamine

1. cocaine
2. amphetamine

Answer 10

1. blocks reuptake of transmitter (dopamine) once released = increased dopamine signal
2. reverses uptake transporter actively expelling DA & NA out of the neuron, preventing DA uptake
   - > ritalin (methylphenidate) used as treatment for ADHD is also a dopamine & noradrenaline reuptake inhibitor

Question 11

Addictive drugs hijack reward response

1. normal
2. addictive drugs

Answer 11

1. when reward is expected NO additional dopamine is released
2. addictive dopamine drugs are ALWAYS coded by the brain as “better than expected” -> forces reward signals to occur

Question 12

Animal “models” of addiction

1. setup
2. result

Answer 12

1. infusion of drugs (heroin/opioid) to animals brain 2. push button to receive more drug at the expense of all other activities/stimulus e.g. food, water
   = animal dies quickly

Question 13

Addiction and dopamine

1. addictive drugs produce
2. the more DA released the
3. the faster the DA release

Answer 13

1. increased dopamine signalling
2. greater the high produced by the drugs
3. the more addictive it will be

Question 14

Addiction and freewill

1. problem 1
2. problem 2
3. final result = addictive behaviour

Answer 14

1. drugs initiate “wanting” and in addicted people lead to cravings
2. cognitive (top-down) control is reduced by impaired function of the prefrontal cortex (PFC) caused by excessive dopamine
   - > imaging studies show PFC abnormalities
3. failures of top-down control would contribute to loss of control over the urger to take drugs

Question 15

Addiction and dopamine

1. while there is a strong link to DA function & addiction…
2. DA system might be more important for…

Answer 15

1. some drugs do seem to cause addiction with less involvement of DA (e.g. nicotine). possibly depending on the opioid system
2. behaviour/habit and cognitive control aspects than the pleasant feeling