L24 & 25- Emotion Fear and Reward

Question 1

Volitional movement have descending _ and _ projections from _ and _ - leading to a _ smile

Answer 1

• “pyramidal” and “extrapyramidal”
• Motor cortex and brainstem
• Pyramidal

Question 2

Neural systems for emotional expression have descending _ projections from _ and _ - leading to a _ smile

Answer 2

• Extrapyramidal
• Medial forebrain and hypothalamus
• Duchenne

Question 3

What is sham rage? What is removed in the brain to result in this?

Answer 3

Undirected unrestricted rage. Removal of cerebral cortex BUT not hypothalamus (key coordinating centre for behaviours that mediate fear – body postures and physiological reactions)

Question 4

What is the role of the limbic cortex (hippocampus and amygdala) in fear? What other structures are involved?

Answer 4

Experience of emotional states

-Limbic lobe, anterior prefrontal cortex, temporal lobe (Amygdala)

Question 5

What is wrong with the papez circuit?

Answer 5

He was wrong because he focuses on the circuit instead. He doesn’t include the amygdala which is the core where fear and fear related experiences come from.

Question 6

3 Divisions of Amygdala (22 in reality but we are looking only at 3)

Answer 6

Central, medial and basal lateral group

Question 7

What’s the difference between implicit and explicit activation of the amygdala?

Answer 7

Explicit – showed pictures and told to rate trustworthiness

Implicit – showed picture and not told to rate but still rates them anyways

Question 8

T/S: Left and right amygdala are symmetrical

Answer 8

False, they are asymmetrical

Question 9

Urban-Wiethe disease – lesions in both side of amygdala in patient SM. What emotion can’t the patient recognise well?

Answer 9

Fear

Question 10

Overactivity of fear circuitry lead to various illnesses:

Answer 10

• Generalized anxiety disorder (GAD)

- Panic attack, panic disorder -Phobias –OCD –PTSD

Question 11

Panic attack symptoms (somatic, cognitive, autonomic) – a whole lot but the ones that stood out to me were feelings of unreality, feeling of being out of control, terror, fear of dying

Answer 11

Panic attack symptoms (somatic, cognitive, autonomic) – a whole lot but the ones that stood out to me were feelings of unreality, feeling of being out of control, terror, fear of dying

Question 12

2 ways to normalise fear responses

Answer 12

1) Re-learning the (mis)associations (e.g. cognitive behaviour therapy)
2) Pharmacological intervention (e.g. GABA, benzodiazepine (GABA agonist), ethanol (partial GABA agonist), barbiturates (sedatives)

Question 13

Patients suffering from anxiety/panic attacks have diminished binding to _____ ______ ____ (particularly frontal insular region)

Answer 13

Inhibitory NT receptor

Question 14

What did Olds and Milner discover?

Answer 14

Self-stimulation sites in the brain

Question 15

What brain regions mediate rewards?

Answer 15

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

Question 16

What is the VTA?

Answer 16

The VTA is a source (via the median forebrain bundle) of dopamine to prefrontal cortex and associated basal ganglia regions. The mode of action of some hedonic drugs (such as opiates) facilitate dopamine release by VTA neurons on frontal regions. Some dopaminergic agonists (e.g. amphetamines) are powerful elevators of mood.

Question 17

Cocaine, Heroin and Nicotine - which areas of the brain do they excite?

Answer 17

Cocaine - Nucleus accumbens/Ventral striatum

Heroin and Nicotine - Dopamine neurons of VTA

Question 18

So what are rats experiencing when they self-stimulate?

Answer 18

It dominates behaviour in rodents, but reports from self-stimulating humans suggests a mental state other than reward (perhaps anticipation of a potential rewarding state).

Addictive behaviour may relate to reward or the anticipatory state (mentioned above), but seems to be dopaminergic.

Question 19

The consideration of the site of drug action often leads to the diffuse modulatory systems of the CNS. These are:

Answer 19

1) A nucleus or cluster of nuclei with relatively few neurons (thousands rather than millions).
2) Most of the nuclei are in the “central core” of the brain: the brainstem and basal forebrain.
3) Each neuron can influence many (maybe hundreds of thousands) of neuron elsewhere in the brain- this is called a highly divergent projection.
4) The synapses made by these cells are typically “en passant” - it means “in passing”, their axons branch and keep making synapses and keep going, passing 1000s and 1000s of neurons.

Question 20

Cocaine and amphetamine affect the amount of dopamine in the NS by

Answer 20

Binding to the receptors and decreasing dopamine reuptake

Question 21

Reward: wanting or enjoying?
Taste liking and disliking behaviours are conserved, involving regions of ventral striatum. Rats depleted of striatal dopamine do not seek food, but exhibit liking and disliking behaviours for palatable (sugar) and unpalatable (quinine) food - hence shows that dopamine is reinforcing the behaviour to obtain the reward, rather than released as a result of the reward itself.

Answer 21

Reward: wanting or enjoying?
Taste liking and disliking behaviours are conserved, involving regions of ventral striatum. Rats depleted of striatal dopamine do not seek food, but exhibit liking and disliking behaviours for palatable (sugar) and unpalatable (quinine) food - hence shows that dopamine is reinforcing the behaviour to obtain the reward, rather than released as a result of the reward itself.

Question 22

When you get the reward, what brain area is stimulated?

Answer 22

Activation of basal part of forebrain, medial septum area.

Question 23

Can reward can undermine motivation?

Answer 23

Yes - when people start thinking about who’s getting rewarded and who’s not.

Question 24

Activity of VTA dopamine neurons is increased during anticipation of reward
e.g. When a monkey is conditioned to receive a reward after a certain stimulus (bell sound), the activity in the VTA increases even before the reward is given to them. If there is a stimulus (bell sound) and no reward is given, the activity of VTA decreases much more compared to how it is at baseline.

Answer 24

Activity of VTA dopamine neurons is increased during anticipation of reward
e.g. When a monkey is conditioned to receive a reward after a certain stimulus (bell sound), the activity in the VTA increases even before the reward is given to them. If there is a stimulus (bell sound) and no reward is given, the activity of VTA decreases much more compared to how it is at baseline.

Question 25

Reward Prediction Error

Answer 25

actual reward now + discounted predicted reward later – predicted reward now

Question 26

• Dopamine is a NT used in a pathway to predict when we are going to get a reward and how rewarding that will be
• Dopamine does other things, and other agents affect reward and motivation.
• The underlying causes of behaviour in experimental animals is difficult to ascribe.
• Dopamine’s locus of action is broad (divergent projections)
• Self-stimulation at high rates does is not associated with concomitantly high levels of dopamine release
• Dopamine depletion leads to anhedonia but does not climate behaviours associated with pleasurable and aversive experiences.

Answer 26

• Dopamine is a NT used in a pathway to predict when we are going to get a reward and how rewarding that will be
• Dopamine does other things, and other agents affect reward and motivation.
• The underlying causes of behaviour in experimental animals is difficult to ascribe.
• Dopamine’s locus of action is broad (divergent projections)
• Self-stimulation at high rates does is not associated with concomitantly high levels of dopamine release
• Dopamine depletion leads to anhedonia but does not climate behaviours associated with pleasurable and aversive experiences.