Lecture 5 reward

Question 1

What are the different types of primary rewards/reinforcers?

Answer 1

Taste 
Odour 
Somatosensory 
Visual 
Auditory 
Other

Question 2

What are some taste rewards?

Answer 2

Salt
Sweet
Unami

Question 3

What are some odour rewards?

Answer 3

Pheromones

Of food

Question 4

What are some somatosensory rewards?

Answer 4

Gentle touch/ grooming
Warm temperature
Washing / bathing

Question 5

What are some visual rewards?

Answer 5

youthfulness/ beauty
Facial expression
“nature”

Question 6

What are some auditory rewards?

Answer 6

soothing vocalisations/ music

Question 7

What are some other rewards?

Answer 7

Attachment 
Sexual behaviour 
exercise 
Play 
Novelty seeking

Question 8

How is reward expressed?

Answer 8

Through pleasure centres

Question 9

What research is there on pleasure centres

Answer 9

• Olds & Milner 1954 discovered
• Electrode stimulation technique: found that rats would ‘work’ for stimulation of specific midbrain sites and felt they had found part of brain for reward.

Question 10

What makes up the basal ganglia?

Answer 10

Caudate nucleus, putamen and striatum

Question 11

What is the ventral tegmental area?

Answer 11

Dopamine expressing neurons

Question 12

What is the substantia nigra pars compacta?

Answer 12

dopamine expressing neurons

Question 13

What does the nucleus accumbens do?

Answer 13

Receives dopamine from VTA

Question 14

What did Heath argue about dopamine?

Answer 14

That dopamine was the happiness drug, and that people would self reward like rats and would crave pleasure and rewarding stimulus more

Question 15

What challenges are there to the dopamine reward hypothesis?

Answer 15

• If you lesion dopamine reward areas leads to loss of learning but not loss of pleasure
• drugs of abuse that target dopamine lead to craving without pleasure
• Heath mis-reported data

Question 16

What are some possible hedonic hotspots?

Answer 16

• Shell of nucleus accumbens (ventral striatum)
• Ventral Pallidum
• Parabrachial nucleus in brainstem
• orbitofrontal cortex?
• Insula?

Question 17

What does the orbitofrontal cortex do?

Answer 17

Reward value and decision making

Question 18

What research looks at reward and value?

Answer 18

Critchley and Rolls (1996)

• Gave drops of blackcurrent on the tongue
• Presented smells of either blackcurrent, apple or banana or non edible
• Cell only active for edible stimulus
• As they get more and more black they don;t want it, so activity in the cell decreases for black but also for apple and banana

Question 19

How is dopamine involved in reward and error prediction in animals?

Answer 19

Monkeys associate light and reward
- before association get baseline firing and spike when they get reward, this is error because they are not expecting reward

• once association learned, get a spike after the light has come on, showing prediction
• On catch trials, they get a dip of activity because they are predicting a reward but they don’t get it.

Question 20

What research has been done into dopamine reward and error in humans?

Answer 20

Similar to animals but using monetary reward,

More firing if they are not expecting a reward and less firing if they are expecting reward.

Question 21

How do dopamine neurons learn to predict?

Answer 21

Hebbian learning strengthens the association between cortical inputs and inputs from the striatum to dopamine neurons if reward is present.

Question 22

What happens if two neurons fire together?

Answer 22

They wire together

Question 23

What is the primary motor cortex always doing?

Answer 23

Planning different actions

Question 24

What does the striatum do?

Answer 24

Plans which actions will go ahead
All information about sensory context will go here
A sort of cross-benefit analysis

Question 25

How does reward driven activation work?

Answer 25

The motor cortex plans actions and sends them to the thalamus, if the thalamus fires, the motor cortex neurons will fire.
The striatum then decides which action should go ahead.

Question 26

What are D1 neurons part of?

Answer 26

The direct pathway- go pathway

They have receptors that make them more likely to fire when there is more dopamine around.

Question 27

What are D2 neurons part of?

Answer 27

The indirect pathway- no go pathway

They have receptors that make them more likely to fire when there is less dopamine around.

Question 28

What are the neurons in the striatum?

Answer 28

Spiny projection neurons which are inhibitory (GABA) neurons that have a low baseline firing rate

Question 29

What are the two types of dorsal striatum firing neurons?

Answer 29

D1 & D2

Question 30

How does the direct pathway work?

Answer 30

D1 neurons connect to the substantia nigra pars reticulata, neurons here are inhibitory but are tonically active (active all the time) these are permanently inhibiting the thalamus.

When D1 started firing they inhibit the neurons they are connected to, so substantia nigra pars reticulata neurons stop inhibiting, meaning they stop inhibiting neurons in the thalamus, so thalamus neurons fire and the signal for the movement to take place happens.

Question 31

How does the indirect pathway work?

Answer 31

D2 neurons are inhibitory and inhibit the globus pallidus external capsule- which has tonically active neurons when these are inhibited, they stop firing and connect to the substantia nigra pars reticulata which then inhibits the thalamus

Question 32

How is it decided which pathway wins?

Answer 32

The substantia nigra pars compacta - if you found action rewarding before then dopamine neurons here start to fire and these are connected to the striatum. If there is more dopamine then the D1 neurons will fire, if there is not much dopamine the D2 neurons will fire.