L15 - Brain Mechanisms of Emotion Part 1 Flashcards
Who is SM?
- Female, mid 20s
- Active life but started having seizures
- Referred to neurologist = no tumour
- Amygdala tissue has atrophied (died)
- Autosomal recessive genetic disease
Why is the amygdala important? and how does this apply to SM?
- Used for fear recognition
- SMs IQ was normal, had no perceptual or motor problems
- BUT was impaired in recognising fearful facial expression via ekman expressions
- SM had a significant deficit in recognising fear expressions
- Asked SM to draw faces that depicted different emotions: had no issues drawing other emotions but did not know how to draw fear
What were the overall takes from SM?
- Impaired recog facial expressions of fear
- No impairment in concept of fear
- No impairment in labelling emotion prosody inc. fear e.g speech sounds that is fearful
- Amygdala plays role in recognising facial expressions of fear
- Selective impairment in recognition of one emotion with spread recog of other emotion suggest distributed nature of emotion processing in the brain (not one single network to process all emotion)
What is the Limbic System?
- Proposed network of regions involved in emotion processing: papez circuit - hippocamous etc
- MacLean extended this network to include amygdala, orbitofrontal cortex and portions of the basal ganglia
- Forms a circle around the corpus collosum = called limbic system
- Now we know, some parts are inaccurate e.g hippocampus is used mostly in memory
What was MacLean’s limbic system theory?
- Some highlighted are important for emotion processing - but not others
Is there one specific circuit for emotion?
PRO:
- Kluver-Bucy Syndrome
- Removed bilaterally the temporal lobes from monkeys inc. amygdala and non-limbic temporal cortex
- Produced dramatic change in monkeys behaviour including theory emotions behaviour
- Monkeys became tame and fearless with flattened emotional response
- This actually came specifically from removal of amygdala
- ablation of amygdala in other species showed similar effects
- Electrical stimulation of amygdala in humans leads to anxiety and fear
What is the anatomy of the amygdala?
- Have two: on each side and near the hippocampus, near the middle
- Small almond shaped structure
What is the relationship between amygdala and facial fear expressions? study
- Humans do not show specific Kluver-Bucy syndrome but we do have deficits
- Presented ppts with ekman faces
- More fear you found in fear = higher response in amygdala = enhanced response to fear faces than happy faces in normal faces
What is fear conditioning?
- Form of classical conditioning where repeating pairings of neutral stimulus with aversive stimulus result in fear response to neutral stimulus alone = now conditioned stimulus
- Done with mice and electric shocks = seen through a freezing response when they’ve been shocked = this stays the same when they have not been shocked
- Amygdala lesioned mice do not show this learning
Is lesion is done after learning = learning association is lost - BUT unconditioned response - natural fear response is not necessarily abolished with lesions
- Amygdala is important for learning and storing conditioned fear response, but not to exhibit fear response
What are the fear pathways in the brain?
- Low road; quick, subcortical pathway = straight to amygdala = automatic = removal of threat quickly
- High road: slower, cortical pathway = goes from visual cortex to thalamus and then amygdala = more conscious
What is the relationship between amygdala and emotional learning in humans? (Study)
- Bilateral amygdala damage patients underwent fear conditioning paradigm
- Pair blue square with shock, and skin conductance increases, when represented with a blue square, the control show higher skin conductance as a fear response but patients do not
- If you ask the patients what happened, the verbalise the association but did not bodily respond to the fear association
- Patients who have hippocampal damage show normal fear response but cannot explicitly recall the association = double dissociation
- Double dissociation suggests the amygdala is necessary for implicit emotional learning and the hippocampus is important for explicit emotional learning
What is the relationship between amygdala and emotional memory in humans?
- Amygdala is good at linking memories e.g memories you think of are strong because they are associated with a strong emotion
- Amygdala plays an important role in memory enhancement through arousal
What was the study looking at the amygdala and emotional memory?
-1) Use patient with amygdala damage
- Looked at memory enhancement through amygdala
- Presented emotional story to ppts, tested their recall of story a few weeks later
- Recall was greater for the emotionally arousing story part
- Amygdala patient had no correlation, and memory was correlated with time = shows it plays part in memory enhancement
2) Emotional vs neutral film clips in PET scanner
- Free recall tested some weeks later
- Recall greater for emotional video clips and recall was correlated with amygdala activity while viewing emotional videos
- Harder the reaction in the moment = the more well remembered
- Therefore amygdala plays role in consolidation of long-term emotional memories
What is the wider role in emotion processing?
- Emotional intensity
- Studies looked at comparing stimuli that have positive/neg/neutral associations = neg responses = greater activity in amygdala
- ppts in scanner looked at different odours and measured amygdala activity = strongest activation was for unpleasant smells
- Replicated for taste also
What is the relationship between the amygdala and individual differences
- Amygdala activation in response to happy faces but only in individuals with extravert personality
