LECTURE 16 - limbic system

Question 1

What is emotion?

Answer 1

• often described as ‘affect’
• combination of psychological and physiological responses to a stimulus
• controversy comes from hard to define normal vs abnormal
• can be +ve or -ve

Question 2

Why have emotion?

Answer 2

• communication
• aids memory
• evidence for importance comes from primary motor cortex - proportion of face is high

Question 3

How do we know the limbic system is linked with emotion?

Answer 3

• Broca (1878) first named the area limbic system
• Papez circuit (1930s) - looking for emotion system, realised there are visible signs of emotion e.g. crying, change in emotional state => change in ANS
• also realised we are consciously aware of emotions

Question 4

What is the Papez circuit?

Answer 4

cingulate gyrus <=> neocortex

cingulate gyrus –> hippocampus –> hypothalamus –> anterior thalamic nuclei –> cingulate gyrus

Question 5

What evidence is there to support the Papez circuits?

Answer 5

• lesions/ tumours of limbic system does => changes in emotional state
• anterior thalamus lesions can lead to spontaneous laughing/crying
• neocortex: PFC - Phineas Gage, changed his emotional state. Oribitofrontal cortex is linked with pleasure

Question 6

Why do we think the amygdala is involved in emotion?

Answer 6

• located in temporal lobe
• made up of corticomedial nuclei, central nucleus and basolateral nuclei
  Animal evidence:
• temporal lobectomy of monkeys=> Kluver-Bucy syndrome; range of behaviour abnormalities most obvious being decreased fear
  Human evidence:
• Urbach-Wiethe disease (patient SM)
• made them fearless and unable to recognise emotional facial expression
• Temporal lobe epilepsy (TBL) - can sometimes tell when they will have seizure
• stimulation of amygdala causes emotional changes as well (also a fear response)

Question 7

How does the amygdala work?

Answer 7

• seems to be in charge of interpreting sensory stimuli and giving a range of outputs
  stimulus –> sensory cortex –> amygdala –> hypothalamus –> ANS + PAG –> behavioural response
  amygdala –> cortex –> emotional experience

Question 8

Can we treat emotional disorders?

Answer 8

• can manipulate circuitry with psychosurgery
• frontal lobotomy used to occur; affected emotional state - no longer acceptable
• modern day approaches: deep brain stimulation, drugs