brain mechanism of emotion Flashcards
S.M case study - amygdala atrophy
Amygdala plays role in recognising facial expressions of fear
Selective impairment in recognition of one emotion with spared recognition of other emotions suggests distributed nature of emotion processing in the brain
MacLean’s limbic system theory (1949/52)
Amygdala, orbitofrontal cortex, portions of basal ganglia
Popularised the term limbic system
Kluver-Bucy syndrome (1939)
First observed when bilateral removal of temporal lobes in monkeys caused dramatic change in emotional behaviour
Anatomy of amygdala
Medial temporal lobes is where you find amygdala
One in each hemisphere
Amygdala and emotional processing
Change in emotional behaviour in Kluver-Bucy syndrome linked to amygdala
Electrical stimulation of amygdala in humans lead to anxiety and fear
Amygdala and fearful facial expression
When fearful expressions viewed in PET scanner, amygdala region had clear linear increase in brain activity
Fear conditioning
Form of classical conditioning where repeated pairings of neutral stimulus with aversive stimulus result in fear response to neutral stimulus alone
Amygdala and fear conditioning
Amygdala lesioned mice do not show fear learning
If animal is lesioned after learning association then the association is lost
Amygdala is important for learning and storing conditioned fear response, but not necessary to exhibit fear response
Fear pathways in the brain - low road
Quick, subcortical pathway
Fear pathways in the brain - high road
Slower, cortical pathway
More conscious route
Fear pathways in the brain
Two pathways allow for a quick response but also a thoughtful process of assessing danger
Amygdala and emotional learning
Double disassociation suggests that amygdala is necessary for implicit emotional learning and hippocampus necessary for explicit emotional learning
Amygdala and emotional memory
Amygdala plays an important role in memory enhancement through arousal
Recall on emotional video correlated with amygdala activity
Huntington’s disease
Genetic disorder with symptoms like excessive movements and cognitive decline arising in mid-adulthood
Insula
Region of cortex lying beneath temporal lobes bilaterally
Located close to primary gustatory cortex involved in early processing of taste
Huntington’s disease and insula
Degree of disgust related impairment is correlated with amount of insula damage
Disgust and the insula
Greater the level of disgust in the expression, the more activity in the insula in neurotypical patients
patient with insula damage selectively impaired in recognition of disgust across modalities, despite understanding concept of disgust
Distaste vs canonical disgust facial expressions
Canonical disgust activates the insula more than distaste
Less likely to react to distaste as that isn’t affecting the observer
Canonical disgust
Lip curl
Related to environment
Distaste
Stick tongue out
Related to bad taste
Insula - beyond disgust
Viewing others in pain also elicits insula activation but modulated by interpersonal relationship between observer and expresser
Anger and orbitofrontal cortex
More anger in a facial expression, the more activity in orbitofrontal cortex
Lesions on orbitofrontal cortex
Causes difficulties in reversal learning and socially inappropriate behaviour
Anger and dopamine
Non human studies have demonstrated altered dopamine activity during aggressive encounter
MAOA
Genetic basis for individual differences in aggression
More pronounced in men
Low activity variant carriers show changes in grey matter volume in amygdala, leading to increased activity in angry faces
Anger in the brain
Facial expressions of anger illicit increased activation in orbitofrontal cortex
Patients with VS lesions impaired in recognition of anger
Administration of dopamine receptor D2 antagonist shows reduction in participants recognition of angry facial expressions
MacLean’s single system model - Specialised group of structures working collectively to form unitary emotion system
Little support for unitary system localised in one specific circuit
If amygdala damaged in a single circuit model then all emotions should be affected but that is NOT the case, essentially disproving the single circuit model
