The Mesolimbic System

Question 1

biological rewards motivate….

Answer 1

behaviour

Question 2

the fact that biological rewards motivate behaviour is learner by what part of the brain?

Answer 2

the midbrain and striatum (the connection between)

Question 3

explain the mesolimbic dopamine pathway

Answer 3

• Cell body in the ventral tegmental (midbrain); sends dopaminergic projections to other regions e.g. PFC
• Medial forebrain bundle: connections between neurons
• Nucleus accumbens (ventral striatum): terminal of neurons here
• PFC (mesocortical)

Question 4

where is the ventral tegmental area?

Answer 4

midbrain

Question 5

what does the cell body in the ventral segmental area do?

Answer 5

sends dopaminergic projections to other regions e.g. PFC

Question 6

what is the medial forebrain bundle?

Answer 6

connections between neurons

Question 7

where is the nucleus accumbens?

Answer 7

in the ventral striatum

Question 8

what happens in the nucleus accumbens?

Answer 8

neurons terminate (contains terminal of neurons)

Question 9

what is Intracranial self-stimulation (Olds and Milner, 1954)?

Answer 9

• Short-circuiting reward
• Rats press the lever to initiate stimulation

Question 10

what did Olds and Milner come up with (1954)?

Answer 10

Intracranial self-stimulation

Question 11

what do dopamine neurons do?

Answer 11

Encode ‘reward prediction error’: learn to change firing in response to a reward and change back if the reward isn’t delivered.

Question 12

what encodes reward prediction error?

Answer 12

dopamine neurons

Question 13

inputs of the mesolimbic system

Answer 13

limbic system, PFC (top-down control of the drive from mesolimbic system)

Question 14

outputs of the mesolimbic system

Answer 14

motor systems
o Basal ganglia (ventral pallidum) = motor initiation
o On to thalamocortical loops

Question 15

where is the basal ganglia?

Answer 15

ventral pallidum

Question 16

rewards stimulate the release of what?

Answer 16

dopamine

Environmental cues which predict reward will cause dopamine release (reward itself doesn’t cause dopamine release)

Question 17

explain the reward/motivation circuit

Answer 17

• Rewards stimulate release of dopamine (unexpected rewards are most potent)
• Dopamine acts as a learning signal
  o Environmental cues which predict reward will cause dopamine release (reward itself doesn’t cause dopamine release)
  o If reward not obtained, dopamine neurons are inhibited
• The actions of this circuit ensure we learn about rewards (especially the environment they are found) and ensure we are highly motivated to obtain them.

Question 18

what rewards are most potent?

Answer 18

unexpected rewards

Question 19

interaction of alcohol and GABA and glutamate

Answer 19

• Alcohol makes GABA receptors work better (inhibitory – so chloride floods into the cell, becomes hyperpolarised and makes AP less likely to fire)

o Inhibits NMDA receptors (for glutamate) so blocks the excitatory groups.
 These receptors then increase to allow the brain to continue working (tolerance).

Question 20

examples of components of the mesolimbic system

Answer 20

ventral tegmental area
nucleus accumbens
medial forebrain bundle

Question 21

components of the limbic system include

Answer 21

hippocampus
hypothalamus
anterior cingulate
amygdala
thalamus

Question 22

components of the basal ganglia include:

Answer 22

substantia nigra
globus pallid us
caudate putamen
caudate nucleus

Question 23

nucleus accumbens is a component of what structure?

Answer 23

the ventral striatum in the mesolimbic system

Question 24

addiction

Answer 24

continued drug use despite known adverse consequences

Question 25

what is this the definition of:

continued drug use despite known adverse consequences

Answer 25

addiction

Question 26

relapse

Answer 26

resumption of drug use after period without, not always motivated by withdrawal or dependence

Question 27

what is this the definition of:

resumption of drug use after period without, not always motivated by withdrawal or dependence

Answer 27

relapse

Question 28

tolerance

Answer 28

requirement to increase dose of drug in order to achieve the same biological effect

Question 29

what is this the definition of:

requirement to increase dose of drug in order to achieve the same biological effect

Answer 29

tolerance

Question 30

dependence

Answer 30

continued drug use to achieve normal biological state

Question 31

what is this the definition of:

continued drug use to achieve normal biological state

Answer 31

dependence

Question 32

an unexpected and new biological reward would lead to what?

Answer 32

would lead to an increase in dopamine release in the nucleus accumbens

Question 33

An expected reward which is then not delivered or is aversive would result in what?

Answer 33

would result in a decrease in dopmine release in the nucleus accumbens