L15: Brain mechanisms of emotion

What did the case study S.M have an impairment in

Recognising fearful facial expressions

What did Adolphs (2003) conclude from his research on S.M

• Amygdala plays a role in recognising fearful facial expressions

• Selective impairment in recognition of one emotion with spared recognition of other emotions suggests distributed nature of emotion processing in the brain

What did James Papez (1937) propose in relation to emotion processing

• James Papez (1937) proposed network of regions involved in emotion processing 

  • Later called Papez circuit

Who developed James Papez (1937) theory of emotional processing

Paul MacLean (1949/52) extended this network to include amygdala, orbitofrontal cortex and portions of the basal ganglia

• Coined the ‘limbic system’

What was the core feature of MacLean’s limbic system theory

Hippocampus

• Argued the hippocampus integrated internal and external information streams

Kluver-Bucy Syndrome (1939)

• Bilateral removal of temporal lobes in monkeys (including amygdala, hippocampal formation and non-limbic temporal cortex) produced dramatic change in monkeys’ behaviour, including their emotional behaviour

• Monkeys became tame and fearless with flattened emotional response

  • Linked to amygdala

What does electrical stimulation of the amygdala in humans lead to

Anxiety and fear

Fear conditioning

Form of classical conditioning where repeated pairings of neutral stimulus with aversive stimulus result in fear response to neutral stimulus alone (now ‘conditioned stimulus’)

The amygdala and fear conditioning

• Amygdala-lesioned mice do not show fear conditioning

• If animal lesioned after learning association, learned association is lost

• BUT, unconditioned response (i.e. natural fear response) not necessarily abolished with amygdala lesions

• Amygdala is important for learning and storing conditioned fear response, but not necessary to exhibit fear response

What might be the wider role of the amygdala in emotion processing (not just fear)

Emotional intensity (?)

• If you smell or taste unpleasant things, greater response in the amygdala

Amygdala: Introvert vs. Extrovert

• Fearful faces activated the amygdala regardless of if the individual had an extroverted personality BUT happy face amygdala activation related to extraversion traits

  • Amygdala activation in response to happy faces BUT only for P’s with extroverted personality

  • Possible amygdala not just related to emotional intensity, but also individual differences

    • Maybe individual differences play key modulatory role

What is the most important feature in fear recognition

Eyes

How was S.M. able to overcome her impairment in recognising fearful facial expressions

• S.M. was using the mouth to identify faces, NOT eyes (why she had fear recognition deficit)

• By instructing S.M. to look at the eyes, S.M. was able to overcome her impairment in recognising fearful facial expressions 

• Conclusion

  • Amygdala plays a role in automatically directing visual attention to the eyes when viewing faces