The Limbic System

Question 1

What is emotion?

Answer 1

• combination of psychological and physiological responses to a stimulus

Question 2

Why do we have emotion?

Answer 2

• emotions can be positive –> approach behaviour
• emotions can be negative –> avoidance behaviour
• important for communication and aiding memory
• a lot of motor cortex is dedicated to facial expression –> must be important, also preserved across species

Question 3

How do we define the limbic system?

Answer 3

• was originally an anatomical definition
• there is not one primary emotion cortex, or cortices for specific emotions
  Structures involved include:
• neocortex, cingulate gyrus, hippocampus, hypothalamus, anterior thalamic nuclei

Question 4

Describe the Papez circuit

Answer 4

• Papez described the ‘emotion system’
  cycle of communication from cingulate gyrus –> hippocampus –> hypothalamus –> anterior thalamic nuclei –> cingulate gyrus
• neocortex communicates with cingulate gyrus also
• emotion included ANS e.g. crying, HR
• emotion included awareness e.g. neocortex and hypothalamus

Question 5

What is the evidence of the Papez circuit?

Answer 5

• Lesions of anterior thalamus –> spontaneous laughing/crying
• Lesions of neocortex e.g. prefrontal cortex –> Phineas Gage –> orbitofrontal cortex, pleasure

Question 6

What is the current view of the limbic system?

Answer 6

• some elements of the Papez circuit not involved in emotion? –> hippocampus, decreased volume in chronic depression
• other parts of the brain also involved include amygdala

Question 7

Where is the amygdala located?

Answer 7

almond size in the front of the temporal lobe

Question 8

Describe the internal structure of the amygdala

Answer 8

• 3 main nuclei
• corticomedial, central and basolateral nuclei
• internal structure –> functional difference

Question 9

What is the evidence for the amygdala being involved in emotion?

Answer 9

• temporal lobectomy in monkeys –> fearless
• Kluver-Bucy syndrome –> rage of behavioral abnormalities including fearlessness
• Urbach-Wiethe disease, degeneration of the amygdala, never felt fear also unable to recognise facial expressions
• temporal lobe epilepsy –> sense of dread before seizure
• stimulation of the amygdala in humans and animals causes a fear response

Question 10

What influences do the central nuclei of the amygdala have?

Answer 10

• influence hypothalamus and then ANS

- also PAG –> behavioural response (behavioural freezing)

Question 11

What influences do the basolateral nuclei of the amygdala have?

Answer 11

–> cortex –> emotional experience/awareness

Question 12

How is the amygdala linked to aggression?

Answer 12

• ## overlap between feat and aggression –> amygdala central to all emotions?

Question 13

Amygdala and Aggression:
What do lesions of basolateral amygdala result in?
What do lesions of the corticomedial nuclei result in>

Answer 13

• decrease affective aggression e.g. fearless

- increase predatory fggresion e.g. hunting

Question 14

Describe the revised circuit of the emotion system

Draw it

Answer 14

now includes the amydala which communicates with the hippocampus, hypothalamus and receives sensory information
draw it

Question 15

What is the clinical arelvetion of a dysfunctional amygdala?

Answer 15

• anxiety disorders e.g. PTSD –> reliving memories
• depression
• autism - facial expression
• aggression
• circuitry dysfunction –> emotional dysfunction

Question 16

How can we manipulate the circuitry to provide treatment for emotional disorders?

Answer 16

Frontal lobectomy - stabilises emotion put cannot feel pleasure, no effect on interlines, reduces anxiety, can affect decision making
Deep Brain Stimulation - into cingulate gyrus, last resort ]
Drugs - anxiety and drepssion

Question 17

What is meant be lateralisation in terms of emotion ?

Answer 17

• right hemisphere specialised for recognising emotions -