Fear and Disgust in the Brain Flashcards
2 dimensional space
Spatial - where the activity/structure/damage occurs
Temporal - when the activity occur
Lesion patient PROS
Naturalistic observation - ecological validity
Can show causal role of damage - changes following lesion
Lesion patients CONS
Damage is not necessarily focal - can affect surrounding connections and pathways which could be causing effects
The cortex can reorganize and form new routes - especially if lesions occur during development
Limited manipulation of variables - observational
Brain stimulation PROS
Direct causal observations with a high level of manipulation/control
Can randomly assign
Brain stimulation CONS
Limited brain coverage
Only possible in some areas of the cortex
fMRI PROS
Good spatial resolution
Shows network activity - other pathways/connections that contribute
High level of manipulation and control, can have random assignment
fMRI CONS
Poor temporal resolution
An indirect measure
Not naturalistic - have to manipulate in an unfamiliar/uncomfortable environment
EEG / MEG PROS
Direct neuronal measure
High temporal resolution
High control
EEG / MEG CONS
Poor spatial resolution
Not in naturalistic settings
Amygdala - role
Thought to be the fear centre
Selective amygdala lesions
Lesions in rodents and monkeys amygdala
Led to impairments in learning about, detecting and responding to physical and social threat
Led to impaired vigilance, avoidance of innate threatening predators, learned dangers - specific
Diminished physiological responses - this response is not specific to but still a large part of a fear response
– supports BET? as BET says parts of the brain for one emotion are specific and accompanied by specific physiology - one region of brain controls all this
Innate threats - Mobbs et al.
Participants laid inside fMRI scanner while tarantula would advance or retreat near their foot
Advancing - amygdala more activated
Retreating - amygdala less activated
– making fMRI more ecologically valid
Innate threats - Mobbs et al.
Participants laid inside fMRI scanner while tarantula would advance or retreat near their foot
Advancing - amygdala more activated
Retreating - amygdala less activated
Amygdala was also more active when the spider was oscillating between - monitoring threat
– making fMRI more ecologically valid
Learned threats - Knight et al.
Paired non-threatening stimuli (light) with a threat (shock) - inducing fear
fMRI scan showed that amygdala responded to light flash - anticipating fear and monitoring how to respond to a learned threat
Patient SM
Complete bilateral amygdala damage due to calcification disease
Minimal damage to the surrounding cortexes
Normal memory, IQ, language and perception
– causal role for amygdala as specific to fear
SM - Fear expressions
Measured whether SM could recognise fear
If amygdala is responsible for monitoring danger, SM should not be able to recognise fear - communicated danger socially
Used Ekman’s faces
Did a ratings task and a forced-choice task
All other emotions were normal, fear was not recognised
SM - conceptualisation of fear
SM has conceptual knowledge of fear and how frightened people behave
Can also categorise different words into a fear category
But can’t conceptually draw a fearful face from memory
Fear faces & amygdala fMRI
Greater amygdala activation for fear expressions than any other
Responded to more in-group - reflecting evolutionary ingroup bias that threats similar people feel may apply to you as well
Theory of constructed emotion + amygdala
Argue that amygdala is responsible for responding to salient stimuli
Amygdala damage isn’t a fear deficit, but an arousal deficit
SM - arousal and valence
SM looked at images and asked to rate valence and arousal
Deficit in recognising how aroused a face showing fear and anger appeared, but normal recognition of arousal in other emotional states
– still specific for fear and anger - could suggest a link between the two main theories? both could work together to give a complex, meaningful emotive experience
SM in naturalistic settings
Reported excitement with snakes and spiders - compulsive urge to touch with curiosity even though reported saying she dislikes spiders/snakes
Showed no signs of nervousness or apprehensiveness in ‘haunted house’ and took leadership roles
Reacted to jump scares with laughing and smiling
- rated fear as 0
When watching movies, abnormal emotional response was limited to fear - not other high arousal states (support BET?)
CO2 challenge: SM
When restricting amount of oxygen, SM showed signs of panic and fear for the first time
BUT when repeating, SM did not experience increased arousal (skin conductance) when anticipating oxygen restriction – no learning from fear
Could be a physiological response to lack of oxygen - instinctive part of body that could be more primitive than emotion
Disgust: role
Origins in distaste - avoidance of diseased food
- motivates to reject, expel or break off contact with the ‘diseased’ thing
Moved into the social-moral domain over evolution
- avoidance of serious social and moral transgressions
Electrical stimulation of insula
Monkey ate things it liked
Certain neurons (generally clustered together) triggered expulsion response to food - not the whole of region
Insula and disgust in humans: Calder et al.
14 healthy ppts
fMRI while viewing pictures of disgusting vs. appetising food
Before scan, measured trait disgust sensitivity
Higher trait disgust had strong linear correlation with increased activity in the anterior insula
– very specific
Also lights up when seeing someone else feeling disgust – support BET as it helps us coordinate social responses and protect others that we care for - empathic response?
NK
Unilateral damage to left anterior insula due to stroke
Otherwise normal IQ, vision, hearing
Emotion recognition was selectively impaired in disgust
