Lecture 25: Reward

Question 1

What has the study of addictive hedonic drugs revealed?

Answer 1

much about the brain mechanisms of reward and motivation

Question 2

Which sites in the brain produce huge self-stimulation responses?

Answer 2

a path from the ventral medial forebrain to the rostral brainstem, centred around a fibre tract called the median forebrain bundle

Question 3

What is the dopaminergic pathway involved in addictive behaviour?

Answer 3

dopamine neurons of the ventral tegmental area which project to the nucleus accumbens

Question 4

What is the ventral tegmental area (via the median forebrain bundle) a source of?

Answer 4

dopamine to prefrontal cortex and associated basal ganglia regions

Question 5

What is the mode of action of some hedonic drugs (such as opiates)?

Answer 5

facilitate dopamine release by VTA neurons on frontal regions

Question 6

What are some dopaminergic agonists (e.g. amphetamines) powerful elevators of?

Answer 6

mood

Question 7

What does dopamine from the VTA + synaptic potentiation result in?

Answer 7

greater inhibition of ventral pallidum
less inhibition of MD thalamus
greater excitation of limbic cortex

Question 8

What is dopamine released in proportion to?

Answer 8

the accuracy to which reward is predicted

Question 9

What is the role of dopamine?

Answer 9

increases the association between cortical inputs and the accumbens

Question 10

What does the prefrontal cortex encode?

Answer 10

values, goals, and how behaviour should be structured

Question 11

What is the accumbens co-activated by?

Answer 11

motivation-state inputs e.g. amygdala, cingulate, brainstem?

Question 12

What happens if some behaviour / cortical activity leads to reward?

Answer 12

something makes the VTA release dopamine (because of the

activity predicted reward) which strengthens that cortex-accumbens association

Question 13

Where are most of the nuclei that dopamine is involved in (diffuse modulatory systems)?

Answer 13

in the “central core” of the brain: the brainstem and basal forebrain

Question 14

What are characteristics of diffuse modulatory systems of the central nervous system?

Answer 14

a nucleus or cluster of nuclei with relatively few neurons (thousands rather than millions)
highly divergent
the synapses made by these cells are typically “en passant”

Question 15

What do reports from self-stimulating humans suggest?

Answer 15

a mental state other than reward (perhaps anticipation of a potential rewarding state)

Question 16

What may addictive behaviour relate to?

Answer 16

reward or the anticipatory state, but seems to be dopaminergic

Question 17

What is significant about taste, liking and disliking behaviours?

Answer 17

are conserved and involve regions of ventral striatum

Question 18

What do rats depleted of striatal dopamine exhibit?

Answer 18

do not seek food, but exhibit liking and disliking behaviours for palatable (sugar) and unpalatable (quinine) food

Question 19

What happens in regards to the activity of VTA neurons when there is no conditioned stimulus and a rat is given a reward?

Answer 19

activity of VTA dopamine neurons increases upon receiving the reward

Question 20

What happens in regards to the activity of VTA neurons when there is a conditioned stimulus and a rat is given a reward?

Answer 20

activity of VTA dopamine neurons increases upon noticing the conditioned stimulus but there is no increase in activity upon receiving the reward

Question 21

What happens in regards to the activity of VTA neurons when there is a conditioned stimulus and a rat is not given a reward?

Answer 21

activity of VTA dopamine neurons increases upon noticing the conditioned stimulus but there is a decrease in activity upon realising that it will not receive the reward

Question 22

What is the definition of dopamine in neuroeconomics?

Answer 22

the amount of dopamine released is about how much reward you thought you were going to get vs. how much you did get