emotion - week 9 part 2 Flashcards
what is emotion regulated by?
the brain
evidence for the brain regulating emotion
clinical observations of patients with neurological damage
- in some cases the consequences of brain damage include an alteration in emotional behaviour and feelings
evidence for the brain regulating emotion
phineas gage
tamping rod through cortex
acident destoryed part of his pre-frontal cortex
unaffected speech, intelligence and memory
seemed to aquire a different personality
- described as reflecting dominance of animal propensities
evidence for the brain regulating emotion
vietnam war veterans
who suffered traumatic damage to ventral preforntal cortex revealed a greater propensity for aggressive and violent behaviour
evidence for the brain regulating emotion
monkeys (1939)
bilateral temporal lobectomies in 15 rehesus monkeys and one cebus monkey
no. of emotional changes (klüver - bucy syndrome in humans)
became tame with an absence or great reduction in fear and anger related behaviour and vocal responses
no hesitation in approaching new objects, animals and people
- normally display substatial neophibia which protects against harm from objects
evidence for the brain regulating emotion
superficial conclusion
temporal lobe and ventral prefrontal cortex mediate -ve emotions
–> fear and anger
however clear from other observations of monkeys showed changes in emotional behaviour were not limited to negative emotions
–> eg. increase in frequency and duration of sexual activity
- implicating the human ventromedial prefrontal cortex in social reward
- human participants showed activation when they were led to believe they were liked by people they admired
evidence for the brain regulating emotion
2 possible interpretations
- different areas within regions of interest mediate the different emotions
- individual brain areas serve common functions different emotions
limbic system
what?
the areas of the brain that mediate emotion
has been modified to accomodate brain areas that have emerged as being important in emotional function
eg. shell of nucleus accumbens (rewards) and cortical areas beyond the cingulate cortex
- this is to ensure the concordance between limbic system and emotion
therefore to say emotion is mediated by the limbic system is a truth that is ensured by its definition as the system that comprises the areas involved in emotion
the amygdala
implicated in what behaviour?
fearful
the amygdala
anatomy
almond shaped structure
deep within temporal lobe
recieves sensory inputs from all modalites
- info arrived both directly from sensory thalamus and also from sensory cortical areas
in a position to coordinate patterns of response
the amygdala
anatomy - downstream
no. of regions w/ functions related to emotional biological responses
- lateral hypothalamus –> HR and blood pressure
- paraventricular nucleus –> release of stress hormone
- periaqueductal grey matter –> freezing response
does the stimulation of the amygdala effect emotional responses?
if amygdala is connected to brain areas responsible for producing emotional responses, it follows that if we stimulate the amygdala this should produce activity downstream in regions t result in emotional states
does the stimulation of the amygdala affect emotional responses?
evidence - monkeys
1964
amygdala stimulation results in increase in HR
does the stimulation of the amygdala affect emotional responses?
evidence - rats
1964
increase HR and blood pressure
1986
corticosterone release into bloodstream
1988
produces fear like behaviour - acoustic startle reflex
does the stimulation of the amygdala affect emotional responses?
evidence - humans
amygdala stimulated in epilect patients
patients reported feeling their heart beating faster and some reported feelings of anxiety or fear
- other studies found might just be fearful of procedure itself
- only a subset of patients experienced these feelings
stimulating amygdala in aggressive patients led to aggressive behaviour
- possible that cognitive context affects the subjective impact of amygdala stimulation
these studies did not take physiological measurements of cardiovascular responses, so cannot make any links between these subjective feelings and any biological responses
does damage to amygdala impair normal emotional response?
just amygdala?
because small and 2cm3 deep in temporal lobe damage from stroke, trauma or surgical resection not limited to amygdala
- also impacts overlying cortex and hippocampus
does damage to amygdala impair normal emotional response?
selective amygdala degeneration
urbach-wiethe disease
patient SM
- appears to show little/no experience of fear
2011
despite hating snakes and spiders showed no hesitation in touching them showing a distinct lack of fear and avoidence
no fear when visiting haunted places
when repeatedly tested on standard questionnaires of fear and anxiety over 3 years scored consitatntly at a much lower level than controls
SM cannot be described as emotionless as she reported high levels of excitement in the haunted house therefore suggesting amygdala plays a role in subjective fear
first implication of amygdala in fear
mid 20thC
bi-lateral lesions to amygdala
- monkeys were tame and showed little neophobia
- showed impairments in experimental fear memory paradigms
—> conditioned avoidance and supression tasks
- light/sound and footshock
- marked reduction in avoidance and supression compared to controls
rats 1990
auditory information must be sent from the thalamus to some other region (primary canditate amygdala)
amygdala and emotional memory
study of SM
looked at her capacity to acquire conditioned fear responses
looked at SM’s physiological galvanic skin response to colours associated with an aversive startling sound
SM showed no evidence of a physiological emotional response –> controls did
amygdala and emotional memory
does impairment of normal amygdala function in experimental animals disrupts fear learning and memory?
huge amount of evidence to suggest yes
however the interpretation of effects on memory of permanent brain damage is complicated
–> reversible brain damage preferable but not current way to do this
amygdala and emotional memory
human functional imaging studies
focused on direct fear processes –> recognition
the amygdala is activated by exposure to fearful facial expressions and this activation is thought to be a necessary mechanism in processing fearful stimuli
urban-wiethe patients are impaired in the recognition of fear in facial expressions
however, while the recognition of fearful expressions may be supported by prior experience + learning it is not obvious from such studies that the amygdala necessarily plays an important role in fear learning and memory
amygdala and emotional memory
pavlovian conditioning procedures 1998
what?
used faces as stimuli - but had neutral expressions and they conditioned them such that the conditioned faces were paired half the time with an unpleasant tone
–> control faces were never paired w/ adversive outcome
amygdala and emotional memory
pavlovian conditioning procedures 1998
was the amygdala activated?
amygdala was activated on both sides during learning of conditioned faces and this activation corrolated w/ magnitude of skin conductance
provides strong evidence amygdala is critically invloved in fear learning in relation to facial stimuli it does not rule out possibility that the human amygdala is somehow specialised for emotional faces
amygdala and emotional memory
1998 - coloured squares + electric shock
shows?
showed same patterns of amygdala activation and skin conductance
amygdala and emotional memory
1998 - coloured squares + electric shock
means?
that involvement of amygdala in fear learning + memory is not limited to specific stimuli and outcomes
assumption is that synaptic plasticity (some) is taking place in the amygdala that mediates the learned fear and this plasticity process is reflected in the enhanced amygdala activity
amygdala and emotional memory
human and animal research
while studies of human fear conditioning seems to corroborate what is known from animal research
- aspects of human emotional learning that can only be studied in humans
- we can simply be instructed to fear a stimulus
- in an experimental situation subjects are told that one stimulus might be associated with a shock whereas, the other stimulus was completely safe
- despite never being any shock presentation of stimulus elicited activity in the left amygdala correlated w/ emergence of skin conductance
amygdala and emotional memory
significance of amygdala activation being unilateral when being told to fear in comparison to bilateral in standard fear conditioning?
not clear
however the existence of an apparently normal fear response after simple instruction may explain how fears can be acquired in a purely social manner