Amygdala

Question 1

Amygdala

Answer 1

• Consists of nuclei (groups of cells)
• Each nucleus has unique inputs and outputs and neurotransmitter systems
• Provides an important route by which external stimuli can have an impact on emotions

Question 2

Nuclei of Amygdala

Answer 2

Lateral nucleus (basolateral group of nuclei) ~ input region/ gatekeeper of amygdala:
- Receives inputs from sensory systems (visual, auditory, somatosensory (including pain), olfactory, and taste systems)

Central nucleus ~ output region for expression of innate emotional and associated physiological
responses
- Connections to brainstem areas that control specific behaviors and physiological responses
- E.g., emotional reactions like “freezing” close a predator

Basal nucleus ~ output to the striatal areas involved in the control of instrumental behaviors
- Actions performed to reach a goal, such as running to safety in view of predator

Question 3

affective processing

Answer 3

Recognition of unpleasant emotions, such as fear and anxiety

Question 4

Role of amygdala

Answer 4

• Important for affective processing
• Associate external stimuli and events with aversive sensory inputs (unpleasant emotions)
- Helps establish emotional significance of external stimuli and events
- E.g., a dark street is associated with physical danger

Question 5

Bilateral damage to amygdala

Answer 5

• Change in emotional behaviour/ hypoemotionality (depends on the extent of damage)
- Decrease in aggression, increase in indifference
- Not necessarily dramatic
• Lack of fear to the stimuli and situations that commonly evoke fear
- Increased exploration of novel environments and objects
• Klüver-Bucy syndrome (i.e., compulsive eating, hypersexuality, docility, hyperorality, etc. ->
reported in animal research)
• But no effect on most memory tests (with selective amygdala damage)

Question 6

Damage to amygdala

Answer 6

impact on social learning rather than a global loss in affective behavior

Question 7

Two aspects of reward

Answer 7

1. Feedback: indicates correct responses on a task
2. Intrinsic value: preference, like and dislike
   - -> amygdala plays role in intrinsic value

Question 8

stimulus-value associations

Answer 8

Linking objects with their current stimulus value
- E.g., associations between a visual appearance of a stimulus (a new food item) with an incentive value
(how it tastes)

Question 9

Damage to amygdala in monkeys

Answer 9

• Disturbed association between new items and their intrinsic value
- Putting non-food items in their mouths
- Abnormal willingness to eat meat or other uncommon foods (olives)
• Greater impact on learning new food preferences than on already-established preferences
• Can distinguish edible from non-edible items

Question 10

Pavlovian fear conditioning

Answer 10

A neutral conditioned stimulus (CS) is paired with an unpleasant unconditioned stimulus

Question 11

Reinforcer-devaluation task

Answer 11

Training:
• Learn to associate the pyramid with cherries and the
cube with peanuts

Bilateral damage to the amygdala

Tests:
• Fed to satiety with cherries, peanuts or given an empty
bowl
• Select one of two objects (pyramid or cube) associated
with food rewards
• Animals with amygdala lesions select an object
associated with a more preferred food, whether they are
satiated or not, because the object value was not updated

Question 12

Bilateral amygdala damage & fear

Answer 12

impairs the recognition and recall of facial expressions of fear
–> compromised social behaviour

Question 13

Amygdala is involved in

Answer 13

• Establishing affective associations
• Registering changes from the neutral status of a stimulus to the affective status
• Establishing unconscious biases and preferences about stimuli (objects, events, people)
• Establishing feelings about abstract ideas, concepts, beliefs, hopes and dreams
• Rational vs. emotional decision making (affective signals influence decision-making)
• Mediating the effect of stress on memory formation and consolidation
• Promotes long-term storage of memories about emotional events

Question 14

Orbitofrontal cortex

Answer 14

• High-level control of affective state
• Cognitive control of amygdala
- “Conquer” fear, appear/act brave despite high heart rate and change in blood pressure
- Phineas Gage had damage to the orbitofrontal cortex -> lack of impulse control

Question 15

Orbitofrontal cortex Contribution to stimulus-reward associations

Answer 15

Amygdala is important for making and updating stimulus-reward associations, while the orbitofrontal cortex is required for storage of such associations

Question 16

Activity of orbitofrontal cortical neurons discriminates between different rewards

Answer 16

• Firing rate reflects the value of expected reward irrespective of the spatial, visual, motor aspects
• Orbitrofrontal cortical neurons represent value in a common mode independent of the type or amount of reward

Question 17

Cingulate Motor Area Function

Answer 17

• Higher-order motor areas
• Processing of information necessary for voluntary action selection
- Based on subject’s internal and external requirements
• CMAr is particularly active when a subject is required to select movements voluntarily in different motor tasks

Question 18

Cingulate Motor Area and Reward

Answer 18

CMAr is critically involved in voluntary motor selection based on the amount of reward:

• Assessment of the reward for the current movement
• Selection of the next movement if the reward is not acceptable

Question 19

Proposed function of the cingulate cortex (including the cingulate motor areas)

Answer 19

• Monitoring of errors and other outcomes
- Detect when actions lead to errors and less rewarding outcomes
- FMRI activity in the cingulate cortex increases when subjects make errors
- Trial-and-error learning
• Encoding a reward prediction based on reward magnitude and reward probability
• Encoding the expected value of actions rather than the expected value of stimuli
- Action-reward relationships are encoded more than stimulus-reward relationships
• Processing the information about the consequences of actions rather than the associations of stimuli
- Removal of the cingulate cortex does not impair learning of visual discriminations