Lecture 21 - Dopamine and Desire

Question 1

What is dopamine?

Answer 1

Dopamine is a neuromodulator that is mainly produced in the Substansia Nigra and Venteral Tegmental Area.

Question 2

What is the amino acid dopamine is synthesised from?

Answer 2

Tyrosine.

Question 3

Is noradrenaline synthesised from dopamine?

Answer 3

Yes.

Question 4

What is the change sequence that tyrosine undergoes to become dopamine and then noradrenaline?

Answer 4

Tyrosine -> DOPA -> Dopamine -> Noradrenaline

Question 5

What is the cause of Parkinson’s disease?

Answer 5

Death of dopamine-producing cells in Substantia Nigra.

Question 6

What are some treatments of Parkinson’s disease and what are potential side effects?

Answer 6

Treatments can include dopamine, such as L-DOPA supplements. Side effects can be hypersexuality.
Deep brain stimulation can also be a treatment option.

Question 7

What is the function of dopamine?

Answer 7

Dopamine has been found to be released when we experience an unexpected “reward”, in anticipation/prediction of a reward, or if the reward is better than we expected. Dopamine function is more do with expectations than it is do with the experience of the reward itself.

Question 8

If a reward is expected and not received what happens to the amount of dopamine released?

Answer 8

Dopamine production is suppressed if the expected reward is not presented.

Question 9

What is the Reward Prediction Error and how does it relate to the function of dopamine?

Answer 9

Dopamine is thought to act as a way of the brain rewarding us for engaging in actions that yield better-than-expected rewards. This drives us to continue to seek out more efficient ways of being and behaving. It is thought to play a key role in evolution.
Dopamine is only released (naturally) if the reward of a task or behaviour is better than expected.

Question 10

If the gain or loss of a reward is unexpected then the associated production or suppression of dopamine is greater.
True or false?

Answer 10

True.

Question 11

What is “opportunity cost” and how does this relate to why ‘cognitive tasks’, such as studying or trying to fix a broken bike?

Hint: dopamine

Answer 11

If we are progressing forward in a task and visibly seeing progress toward a goal then we will release dopamine and want to continue on with that task.
If we are not experiencing the benefits of a task as we are engaging in it, and it is a long task, such as stiudying we will not release dopamine and our brain will feel that we are wasting opportunities to achieve our goals elsewhere. This is known as opportunity cost and it is a cognitive process that is thought to be related to dopamine function.

Question 12

Why is gambling so addictive?

Hint: think about the effect unpredictability has on the effects of dopamine

Answer 12

Gambling so addictive because dopamine is only released when we win, and not when we lose. Therefore our brain codes for wins more strongly and seeks them out as opposed to coding for the losses and making us avoid the behaviour. Because the wins are unpredictable the behaviour is more addictive because each trial has the possibility of being a win.

Question 13

What is the definition of an addiction?

Hint: adverse consequences

Answer 13

Addiction can be defined as a behaviour that persists despite adverse consequences and prevents engagement in life activities.

Question 14

How does cocaine affect dopamine function and why does this make cocaine addictive?

Answer 14

Cocaine prevents the re-uptake of dopamine and therefore dopamine is in the synapse longer and can have an affect on the post-synaptic neurones longer.

Question 15

How does ice/speed/amphetamines affect the action/presence of dopamine and how is it different to how cocaine works and again, how does this make it highly addictive?

Answer 15

Methamphetamines are a class of drug that hijak the dopamine pathway.
They work by both preventing the reuptake of dopamine by the presynaptic neuron, and also causing an increase in dopamine release into the synapse.
This is different to cocaine which just prevents the reuptake of dopamine by the presynaptic neuron.
This is why methamphetamines are so addictive.

Question 16

Addictive drugs hijack the reward pathway.
True or false?

Answer 16

True.

Question 17

What is noradrenaline and what role does it play in addiction/certain addictive drugs, such as ice?

Question 18

What effect do addictive drugs that hijack the reward pathway/dopamine pathway have on the prefrontal cortex and how does this further the addiction?

Answer 18

The excessive release of dopamine decreases the function of the prefrontal cortex, which leads to an decreased ability to engage in rational and logical thought.

Question 18

What effect do addictive drugs that hijack the reward pathway/dopamine pathway have on the prefrontal cortex and how does this further the addiction?

Question 19

What are the two areas in the brain that have neurons that produce dopamine?

Answer 19

The Substantial Nigra (SN)- these dopamine neurons are associated with motor control.
Ventral Tegmental Area (VTA) - these dopamine producing neurons are considered to be more involved in the emotions, motivation, addiction, reward and desire.

Question 20

What is the amino acid that dopamine is synthesised from?

Answer 20

TYROSINE.

Question 21

What is the pathway of dopamine synthesis and then noradrenaline synthesis?

Answer 21

Tyrosine - DOPA - dopamine - noradrenaline

Question 22

What is noradrenaline synthesised from?

Answer 22

Noradrenaline is synthesised from dopamine.

Question 23

What can L-DOPA be used to treat?

Answer 23

Parkinson’s disease

Question 24

What is the link between Parkinson’s disease and dopamine?

Answer 24

Parkinson’s disease is caused by death of neurons in the SUBSTANTIA NIGRA

Question 25

Can Parkinson’s be treated with Deep Brain Stimulation?

Answer 25

Yes.

Question 26

What is the reward prediction error and how does it relate to the function of dopamine?

Answer 26

Dopamine is considered to be released when the reward experienced is more than what was expected or if it is completely unexpected.
This is why when taking drugs or substances that cause a release of dopamine you need to take higher and higher doses or do the behaviour more and more or more intensely/extremely to get a release of dopamine.

Question 27

If gains or losses are unexpected the emotions associated with those experiences will be more intense.
What does this have to do with dopamine?

Answer 27

The fact that dopamine fires when the reward is unexpected or better than expected may be a way that our brains help us turn toward activities that yield better than expected rewards.

Question 28

What role is dopamine thought to play when it comes to cognitive/physical effort and reward?

Answer 28

Dopamine is thought to help us weigh up the costs/benefits of a task and determine whether it is worthwhile that we persist.

Question 29

Why is gambling so addictive through a dopamine lens?

Answer 29

Losing when gambling is expected. Winning when gambling is unexpected. This means that even though someone may have lost most rounds their brain will disproportionally release dopamine for the win and therefore the person will continue to try and get that feeling again. The unpredictability of gambling is what contributes to its high addictive nature.

Question 30

What determines whether an activity is considered an addiction?

Answer 30

A compulsive pattern that persists despite adverse consequences and prevents or impairs ability to engage in other activities.

Question 31

How does cocaine work?

Answer 31

Cocaine prevents the re-uptake of dopamine.

Question 32

How does ice (methamphetamine)/speed affect the dopamine pathway and why is it so addictive?

Answer 32

Methamphetamines not only block the re-uptake of dopamine, but they also increase the release of dopamine.

Question 33

Why are drugs that hijak the reward pathway more addictive than behaviours that can addictive?

Answer 33

Drugs, such as cocaine or methamphetamines, are more addictive because they always cause a spike in dopamine. Behaviours that can be addcitive, such as sex, need to be continually altered, changed, expanded on in order for the reward of the act to be. “better than expected” and cause a release of dopamine.

Question 34

The more a drug causes the release of dopamine and the faster it acts the more addictive a substance will be.
True?

Answer 34

True.

Question 35

Why is ritalin not very addictive?

Answer 35

Ritalin, whilst a form of methamphetamine, is not very addictive, if at all. This is because it is a slow releasing medication and therefore the association between taking the medication and it causing an increase in dopamine release is not made. Also means that the dopamine release is gradually increased, as opposed to all at one, like other addictive methamphetamines, such as ice.

Question 36

What two factors discussed that make drug addiction (for drugs that hijack the dopamine pathway) so difficult?

Answer 36

The use of dopamine hijacking drugs creates cravings and urges and also elicits doapmine release without any action.
Excessive dopamine release in the brain can lead to impaired/decrease in functioning of the prefrontal cortex, which is important for logical/rational thinking.

Question 37

Level of dopamine release is not necessarily the reason why certain drugs are so addictive.
It appears that drugs that work on dopamine and opioid systems are most addictive.
What role is thought that dopamine plays in regards to addiction then?

Answer 37

It is thought that dopamine is more involved in the habit/behavioural aspect of the addiction and less involved in the “Reward” aspect of the addiction. The reward aspect may be more to do with opioid action.

Question 38

Addictive drugs that cause the release dopamine are always encoded as…..?

Answer 38

Better than expected by the brain, because in a natural setting dopamine only fires if the reward is better than expected.