Fear And The Amygdala Flashcards
Emotions: Overview
- are measurable changes in the autonomic nervous system
- reactions are frequently aimed at protecting onself
–> sympathetic system: utilising resources in challenging or threatening situations (fight-or-flight response)
–> parasympathetic system: building up metabolic reserves - two fundamental dimensions: arousal and valence
Amygdala
- multiple subnuclei (>14)
Three major subdivisions of amygdala:
- medial (olfaction)
- basolateral (cortical input)
- central (hypothalamic output)
- projects to hypothalamus
- links cortical regions (sensory information) with hypothalamic and brain stem effector systems
–> crucial linking cortical cognitive states (fear, surprise, happiness) to the according somatic reactions - many neurons in amygdala respond specifically to visual, auditory, somatosensory, visceral sensory, gustatory or olfactory stimuli
- processes both raw sensory inputs from thalamic nuclei and highly processes inputs from cortial regions
- facilitates associative learning by linking neutral stimuli to primary reinforcers
- mediates the association of sensory stimuli with emotional significance
Locationist approach to emotion
Key concepts:
- emotions correspond to specific brain regions
–> amygdala = fear
- anatomical locationism assumes distinct regions for specific emotions
- homological locationism focuses on inherited neural networks shared with other mammalian species that involve subcortical circuits
Challenge
- overlap in brain activity questions strict region-emotion mapping
What is fear conditioning?
= a form of emotional learning where a neutral stimulus (CS) becomes associated with an aversive event (US) –> triggering a fear response
Fear conditioning: key pathway
LA: sensory interface for CS and US inputs
CE: projects to brain regions (eg hypothalamus) for fear responses
Fear conditioning: amygdala input routes
Fast route
- imprecise
- via sensory thalamus
Slow route
- detailed
- via sensory cortex
Biological and inherited emotions
Universal expressions - Ekman (1971)
- humans from different cultures show similar facial expressions
Emotions in infants
- cogenitally blind infants produce similar facial expressions as sighted infants
- newborns exhibit basic emotional expressions (eg crying, smiling) without learning them
Animal studies
- mice show fear response withput learning
==> emotions are biologically hardwired, not just learnt
What is Urbach-Wiethe disease?
= almost complete bilateral destruction of amygdala
–> sparing of hippocampus and neocortical structures
- casues severly impaired fear response
- normal IQ, intact memory, language and percpetion
==> example is patient SM
- able to recognise faces
- able to recognise other emotions but fear
–> severe lack of recognising fear
What is fear induction?
= exposure to stimuli capable of triggering state of fear
Patient SM (Urbach-Wiethe-disease)
- did not show fear response
- AND did not report having fear
What is fear experience?
= is the subjective feeling of fear
Patient SM
- experience-sampling to measure emotions in daily life
- history studied to detect events that might cause fear
- 8 self-report questionnaires over 3 years
–> all fear experiences significantly lower than normative mean
(- other emotions normal)
Why is SM a special case for locationists?
- findings indicate that amygdala is crucial for fear
- bilateral amygdala damage causes impaired fear response
- impairments with fear specific recognition
- intact experiencing and processing of other emotions
- no cognitive impairments reported
–> support for locationists account
What evidence exists against localists account?
- inhaling of CO2 can provoke air hunger, fear and panic attacks
In case of SM (bilateral amygdala lesions) reduced CO2 evoked fear expected
- BUT at 35% CO2 –> SM reported fear (first time since childhood)
- findings were replicated with other patients
Localist account: What is uniqueness?
= one-to-one mapping
- a given brain region should be active only when a specific emotion is exprienced
–> eg amygdala should be active solely during fear
BUT
- emotion related brain regions are also active for other emotions
- eg amygdala is found to be more involved in experience of disgust than fear
Localist account: What is consistency?
= a brain region should be consistently active every time the emotion if felt
–> across individuals
–> across contexts
BUT
- some patients with bilateral amygdala damage can regonise fearful faces
- ans show acoustic startle response
Theory of constructed emotion
- emotions are constructed based on valence and arousal
–> not innate
–> dynamically constructed through language, culture and cognitive processes - made meaningful through cognitive processes
- different networks combine and constrain one another like ingredients in a recipe
- influencing and shaping one another in real time
