lecture 10: emotion 1 Flashcards
What is EMOTION?
A discrete affective response indicating the salience/value of an internal or external event comprised of:
– Klaus Scherer: “interrelated, synchronized changes in the states of all or most of the five subsystems in response to the evaluation of an external or internal stimulus event as relevant to major concerns os the
organism”
– Joseph LeDoux: Subjective Feelings
parasympathetic system (rest and digest)
The parasympathetic nervous system predominates in quiet conditions while the sympathetic nervous system drives the “fight or flight” response in stressful situations. The main purpose of the PNS is to conserve energy to be used later and to regulate bodily functions like digestion and urination
sympathetic system (fight or flight)
Your sympathetic nervous system is best known for its role in responding to dangerous or stressful situations. In these situations, your sympathetic nervous system activates to speed up your heart rate, deliver more blood to areas of your body that need more oxygen or other responses to help your get out of danger
CRF
Cortocotropin
releasing factor released by the thalamus
Corticotropin-releasing hormone (CRH; previously known as corticotropin-releasing factor) is the central regulator of the hypothalamic-pituitary-adrenal (HPA) axis, which is the main organizer of the body’s response to stress.
ACTH
Adrenocorticotropic hormone (ACTH) is a tropic hormone produced by the anterior pituitary. The hypothalamic-pituitary axis controls it. ACTH regulates cortisol and androgen production. Diseases associated with ACTH include Addison disease, Cushing syndrome, and Cushing disease
Mood
Diffuse affect state, characterized by a
predominance of subjective feelings that affect the experience and behavior of the person. May be longlasting, and not event focus
an emotion can trigger a mood, which is longer lasting
Affect Dispositions
Stable personality traits and dispositions that have an affect core. The tendency of a
person to experience certain moods (anxious, jealous).
Can also describe psychopathologies
Social Emotions
Love, Guilt
Parsing emotional experience
A widely accepted theory of basic emotions and their expressions, developed Paul Ekman, suggests we have six basic emotions. They include sadness, happiness, fear, anger, surprise and disgust
Cross cultural affect labels
– around 35 (Scherer, Keltner)
There are a few primary dimensions to emotional
experience:
Valence (good-bad) and Arousal (how
intense).
Three Theories of Emotion:
The interaction between subjective experience and physiological state
james-lange theory
cannon bard theory
schachter singer two factor theory
james-lange theory
The James-Lange theory of emotion suggests that physical changes in the body happen first, which then leads to the experience of emotion. Essentially, emotions stem from your interpretation of your physical sensations. For example, your heart beating wildly would lead you to realize that you are afraid
problem: Another criticism of the James-Lange theory is that physical reactions don’t have a single corresponding emotion. For instance, heart palpitations could suggest fear, excitement, or even anger. The emotions are different, but the physical response is the same.
cannon bard theory
The Cannon-Bard theory of emotion states that stimulating events trigger feelings and physical reactions that occur at the same time. For example, seeing a snake might prompt both the feeling of fear (an emotional response) and a racing heartbeat (a physical reaction).
problem: One of the predominant criticisms of the Cannon-Bard theory is that it assumes that physical reactions don’t influence emotions. However, a large body of research on facial expressions and emotion suggests otherwise.
schachter singer two factor theory
Schachter and Singer’s (1962) Two-Factor Theory of Emotion suggests that physiological arousal determines the strength of the emotion, while cognitive appraisal identifies the emotion label. So, in this theory, the “two-factor” represents physiological change and cognitive appraisal change.
For example, if you were to see a venomous snake in your backyard, the Schachter–Singer theory argues that the snake would elicit sympathetic nervous system activation (physiological arousal) that would be cognitively labeled as fear (cognition) based on the context.
problem: However there are many weakness of the method used by Schachter and Singer. The experiment definitely lacked ecological validity. We do not usually experience emotions in the way in which Schachter and Singer induced them.
Neural Systems of Emotional Processing
Early concept: The Limbic System
Papez (1932) proposed a circuit of neural structures involved in emotional processing including: hypothalamus, anterior thalamus, cingulate gyrus and hippocampus
- Maclean (1949), inspired by demonstrations of Kluver-Bucy Syndrome, named these structures “Papez Circuit” and extended the network of emotion to include the amygdala, orbitofrontal cortex and portions of basal ganglia. This
extended system was called the “limbic system”
Kluver-Bucy Syndrome:
Bilateral Damage to Medial Temporal lobe
Kluver-Bucy syndrome (KBS) is a rare neuropsychiatric disorder due to lesions affecting bilateral temporal lobes, especially the hippocampus and amygdala. It is characterized by hyperorality, hypermetamorphosis, hypersexuality, bulimia, placidity, visual agnosia, and amnesia
*Problems with limbic system concept:
Unclear why some structures are “limbic” and not others, what is the criteria for a
limbic structure?
– Some limbic regions originally thought to be primarily involved in emotion are now
known to be more important for non-emotional, cognitive behaviors (e.g.,
hippocampus)
– No evidence these regions represent a ‘system’ or ‘circuit’ of emotion
– Because of these issues, some have suggested abandoning the ‘limbic’ system concept
– Terms “limbic system” or “limbic” regions are still used today, primarily because of inclusion of orbitofrontal cortex and amygdala
what part of the brain is involved in Acquiring fear/threat
amygdala
How do objects and people acquire emotional
significance?
what part of the brain is involved in Controlling fear/threat
amygdala and prefrontal
cortex
– How do we alter emotional significance?
Ivan Pavlov
In the study of digestion, Pavlov observed that the experimental dogs salivated when fed red meat. Before feeding a dog, Pavlov might set a metronome at, say, sixty beats a minute. The next time the dog heard a metronome at any speed, it would salivate. But when only that particular metronome setting was reinforced with food the dog became more discriminating
Classical conditioning theory states that behaviors are learned by connecting a neutral stimulus with a positive one, such as Pavlov’s dogs hearing a bell (neutral) and expecting food (positive). The learned behavior is called a conditioned response
Pavlov’s famous experiment of the drooling dog shows that there are two types of reflexes: innate reflexes that are evoked by the irritant itself and acquired reflexes that are evoked by subsequent associations’
The Amygdala Fear/Threat Circuit
Sensory information converges in the lateral nucleus (LA - site of memory storage), which projects to the central nucleus (CE), which projects to the
brainstem/hypothalamus
The amygdala can respond to learned threats quickly, prior to full sensory
processing, via projections from the sensory thalamus (LGN, MGN)
amygdala
The amygdala participates in the regulation of autonomic and endocrine functions, decision-making and adaptations of instinctive and motivational behaviors to changes in the environment through implicit associative learning, changes in short- and long-term synaptic plasticity, and activation of the fight-or-flight response
Like other animals, the human amygdala is necessary
for the physical expression of a learned
aversive response in fear conditioning
Threat Conditioning in Humans
- This simple model of threat learning applies to the social communication of threat
- Cognitive (language) and social
(observation) means of threat learning takes
advantage of phylogentically older
mechanisms of fear conditioning
Germs
the social communication of fear/threat
Mechanisms of Threat/Fear Control
Two techniques currently used clinically
extinction
cognitive emotion regulation
Extinction
– Forms the basis for exposure therapy
Amygdala BOLD Decreases During Extinction
vmPFC BOLD Increases During Extinction
Exposure therapy is a type of therapy in which you’re gradually exposed to the things, situations and activities you fear. There are a few different approaches to this therapy. It can help treat several conditions, like phobias, post-traumatic stress disorder (PTSD) and panic disorder
- Cognitive Emotion Regulation
– Forms the basis for cognitive therapy
Cognitive behaviour therapy (CBT) is a type of psychotherapy. It may help you to change unhelpful or unhealthy ways of thinking, feeling and behaving. CBT uses practical self-help strategies. These are designed to immediately improve your quality of life. CBT can be an effective way to treat depression and anxiety.
what part of the brain is necessary
for the learning and retrieval of
extinction
The ventral medial prefrontal
cortex (VMPFC)
amygdala
plays a role in the acquisition of extinction
flashbulb memory
A flashbulb memory is an accurate and exceptionally vivid long-lasting memory for the circumstances surrounding learning about a dramatic event. Flashbulb Memories are memories that are affected by our emotional state
The Amygdala Fear/Threat Circuit
The Prefrontal Cortex inhibits the expression of the threat memory to allow the expression of the safe (extinction) memory and the cognitive regulation of
threat memories
explain relapse following extinction
Following extinction and emotion regulation
threat/fear reactions are susceptible to relapse under stress, passage of time, context shifts and other reexposure to the US
This is reflected clinically in the relapse rate following
exposure and/or cognitive therapy
* Can we enhance the persistent control of threat using novel techniques?
– Reconsolidation
explain a study of reconsolidation
Memory consolidation is a category of processes that stabilize a memory trace after its initial acquisition
Studies in rats block the reconsolidation of memory (and erase the fear) by injecting protein synthesis inhibitors into the amygdala during the
reconsolidation window
not safe in humans
targeting reconsolidation May prevent the relapse of threat responses by reducing
dependence on prefrontal inhibitory mechanisms, but successful clinical translation may be difficult
How do scientists think about emotion?
- Basic emotions (as seen through facial expression)
- Dimensions of emotion (as reactions to events)
Basic emotions
People all of the world show pretty much the same facial
expressions for 6 basic emotions:
High agreement for anger, happiness, disgust, surprise, sadness,
and fear
Basic emotions: Ekman’s “Universal Facial Expressions”
Anger, happiness, disgust, surprise, sadness, fear
- Basic emotions
(as seen through facial expression)
- Dimensions of emotion
(as reactions to events)
Emotions tap into a “core affect” system and are
CONSTRUCTED as reactions to events along continuous
dimensions
* Example:
VALENCE (negative – positive)
vs.
AROUSAL (low – high)
VALENCE
(negative – positive)
AROUSAL
(low – high)
- Emotions involve a core affect system with two primary dimensions:
pleasantness and activation
l* Emotions are constructed by combining this core affect system with
thought, language, and theory of mind
* pleasantness = valence
* activation = arousal
- Basic core emotions (according to Ekman) as revealed by facial expressions:
anger, happiness, disgust, surprise, sadness, and fear
* Appears that there are a basic set of emotions that have universal expression (across culture, infants, blind)
* But does not deny that at least some emotions are constructed (e.g., combinations
of 2 or more basic emotions)
alternative dimensional approach
focuses on emotion as constructions that
vary along continuous dimensions in response to events
* ALL emotions are constructed in reaction to some stimulus in your environment
* Example: The experience and expression of anger can be very different depending on
who/what elicits it (i.e., “constructed” in response to a friend betraying you, your dog
chewing your shoes, your younger sibling messing with you, etc
Fear conditioning:
A form of classical conditioning in which
a neutral stimulus (e.g., light) acquires aversive properties by
virtue of being paired with an aversive event (e.g., shock)
conditioned stimulus
A conditioned stimulus is a stimulus that can eventually trigger a conditioned response. In the described experiment, the conditioned stimulus was the ringing of the bell, and the conditioned response was salivation
unconditioned stimulus
causes a response without any prior learning on the part of the subject. The response is automatic and occurs without thought
For example, if the smell of food (the unconditioned stimulus) had been paired with the sound of a whistle (the conditioned stimulus), the sound of the whistle would eventually come to evoke the conditioned response of hunger
conditioned response
an automatic response established by training to an ordinarily neutral stimulus.
unconditioned response
An unconditioned response is an automatic response to a stimulus. The dogs salivating for food is the unconditioned response in Pavlov’s experiment. A conditioned stimulus is a stimulus that can eventually trigger a conditioned response
Extinction
After repeated presentation of conditioned
stimulus (light) without the unconditioned stimulus (shock),
the rat will no longer show startle to the light alone
Amygdala Lesions in Emotional Learning
Lesions to rat amygdala do not affect
natural response to fear-inducing stimuli
(will still startle in response to shock,
loud noise)
* Fear expression is intact
However, lesions to amygdala do
prevent learning of the conditioned
startle response (e.g., won’t startle from
light alone)
* Impaired conditioned fear
Amygdala
Your amygdala is a small part of your brain, but it has a big job. It’s a major processing center for emotions. It also links your emotions to many other brain abilities, especially memories, learning and your senses. When it doesn’t work as it should, it can cause or contribute to disruptive feelings and symptoms
Amygdala is connected to many other parts of cortex
(sensory cortex, MTL, etc.)
Inputs from multiple brain regions converge on the
lateral nucleus (LN) of the amygdala
what part of the amygdala is critical binding the association between
pain (from shock) and unconditioned stimulus (light)
lateral nucleus of the amgydala
LN projects to central nucleus (CN), which is connected to parasympathetic and
sympathetic nervous systems (to activate an emotional response)
damage to what part of the amygdala severely disrupts fear conditioning
Damage to lateral nucleus or central nucleus
amygdala
- Inputs from multiple brain regions (e.g., sensory areas, MTL, etc.)
converge on lateral nucleus (LN) of amygdala, the main input
center of the amygdala - This pattern of convergence allows for the formation of
associations that underlie fear conditioning (e.g., pairing pain from
the shock with seeing the light) - LN projects to central nucleus (CN) of amygdala, which is well
connected to parasympathetic/sympathetic nervous system - Projections from LN to CN initiate will initiate an emotional
response (e.g., fight/flight) if a stimulus is determined to represent
something threatening or dangerous
Thus, damage to LN or CN severely disrupts fear conditioning.
Conditioned Fear in Humans
Conditioned with a blue square (conditioned stimulus) and a
mild electric shock (unconditioned stimulus)
* Dependent measure: Skin conductance response (SCR)
Skin conductance response (SCR)
- Place electrodes on fingers
- Hook up to measuring device
- Measures autonomic arousal
the conductance is measured by placing two electrodes next to the skin and passing a tiny electric charge between the two points. When the subject increases in arousal, his/her skin immediately becomes a slightly better conductor of electricity because they sweat
Unlike the epidermis and dermis layers of our skin — which are poor conductors of electricity — our sweat is rich with electrolytes such as sodium and chloride, which makes our sweat a surprisingly decent conductor of electricity (though not quite as good as metal)
Healthy subjects show an increase in SCR when they experience something
emotionally arousing (can be pleasant or unpleasant)
Case Study: Patient S.P.
- Bilateral amygdala damage
- Although normal subjects show increased SCR after
conditioned fear, Patient S.P. does NOT show increased SCR to
conditioned stimulus (i.e., no emotional learning) – impaired
implicit learning
Patient S.P.’s explicit learning is intact à she explicitly
learns that blue square = shock, even though no SCR
response
double dissociation with amygdala
- Although normal subjects show increased SCR after
conditioned fear, Patient S.P. does NOT show increased SCR to
conditioned stimulus (i.e., no emotional learning) – impaired
implicit learning - Patient S.P.’s explicit learning is intact à she explicitly
learns that blue square = shock, even though no SCR
response - What pattern of results would you expect for someone with
damage to the hippocampus but intact amygdala? - No explicit memory of the pairing (e.g., don’t remember seeing
blue square) - Intact implicit memory, showing a normal conditioned fear
response (increased SCR) to the blue square - Thus, double dissociation!
What pattern of results would you expect for someone with
damage to the hippocampus but intact amygdala?
No explicit memory of the pairing (e.g., don’t remember seeing
blue square)
* Intact implicit memory, showing a normal conditioned fear
response (increased SCR) to the blue square
2 Pathways to the Amygdala
- Low road
- High road
low road pathway to amygdala
Sensory information goes from thalamus to
cortex (e.g., VMPFC) for more elaborate processing, then routed
to amygdala à slow but more accurate analysis
high road pathway to amygdala
Sensory information goes directly from thalamus
to amygdala à fast and crude analysis
– Good for quick action upon detecting threat
name 2 things that support Schachter-Singer two-factor theory
- Misattribution of arousal supports this framework
- Excitation transfer supports this framework
Misattribution of arousal
- Participants injected with epinephrine without their knowledge
- Drug alone did not cause participants to report emotion
- James Lange Theory would predict that the drug alone should cause emotion
- The presence of a grumpy or happy person did
- Drug made the reported emotions more intense (in either direction!)
Excitation transfer
- Emotional responses can be intensified by arousal from previous stimuli not
directly related to the stimulus that originally provoked the response - When a person becomes aroused physiologically, there is a subsequent period
of time when the person will experience a state of residual arousal yet be
unaware of it - If additional stimuli are encountered during this time, the individual may say
their emotional response is more intense to the additional stimuli
Encoding
the is the interface between STM and LTM à How
we perceive and interpret our experiences
How does emotion affect encoding, or how we perceive our
experiences?
- Captures attention
- Improves perception and memory for central event
- Decreases memory for non-emotional items that occur at the same time
Evidence that Emotion affects encoding by capturing our attention and
improving perception
- The Emotional Attentional Blink
- Visual perception enhancement experiment
Attention selection over time: The
attentional blink paradigm
If a second item is right after the first, it is often
missed. If it is presented later, participants catch it.
Demonstrates attention selection over time
The increase in detection for ‘early’ words is evidence for
improved attention during emotional processing
- Emotional arousal improves perception
- The amygdala influences perception to ease/improve processing
Which brain regions are responsible for increasing attention for
emotional information
amygdala
Emotion and encoding: visual
perception enhancement
Cue attention with a face in one location. The face is either fearful
or neutral
* Task: detect specific gabor patches in that location
* If the face is fearful, participants are able to detect fainter patches.
* If fearful faces all over (no relationship to where the gabor appears), there is no benefit to attention.
* Take home point: emotion enhances perception
- Emotion enhances perception and perceptual benefit of attention
Emotions distracts from non-central
information
- Fearful faces direct attention away from the the location
where a dot will appear. - Participants are slower at finding the dot when this happens
Why?
* The parietal lobe is involved in voluntarily shifting attention
* If a fearful face is presented on the right side of the visual field, the
left parietal lobe (which is responsible for shifting attention in that
visual field) does not activate as much -> lower ability to attend to
other information
Flashbulb memories
Kennedy’s assassination, the Challenger space shuttle explosion and, more recently, the 9/11 attacks. Known as “flashbulb memories,” these detailed recollections can be as clear as something that happened yesterday, right down to the dialogue, the weather and even what people were wearing when they heard the news
amygdala and hippocampus
- Based on neuroimaging and patient data, a number of researchers have proposed that during emotional arousal, the amygdala modulates activity in
hippocampus, resulting in improved memory for positive and negative stimuli,
most likely as a result of stronger encoding and less forgetting of the positive and negative items
Emotion and storage (or consolidation)
- Emotion prevents memories from being forgotten because of
interactions between the amygdala and the hippocampus - Evidence:
- Emotional and non-emotional stimulus forgetting
Emotion and retention: patient evidence
- Study a series of taboo and
neutral words - Asked to recall the words after
a delay - Controls did not forget as
many taboo words as neutral
words - Amygdala patients show no
such benefit of emotional
words on consolidation
Remember/Know
in the remember–know–new paradigm (Tulving, 1985), participants are first given a study list, and they are subsequently presented with a test list consisting of previously studied (old) and new items. Participants judge whether each test item is new or old. If they judge the item as old, then they further judge whether they remembered the item or knew it. According to proponents, the endorsement of a remember response indicates a conscious, recollective recall, and the endorsement of a know response indicates automatic activation based on familiarity.
Emotion and Retrieval
Independent neural systems underlie the subjective sense of
remembering for emotional and neutral scenes
The amygdala is involved in ‘remembering’ emotional words. The parahippocampus is involved in both, but more for neutral
Parahippocampus and amygdala show opposite patterns:
* Amygdala responds more to remembered emotional scenes than
just known emotional scenes
* Parahippocampus responses more to remembered neutral scenes
than just known neutral scenes
Parahippocampal cortex: Emotion and Retrieval
- Effect of remembering vs knowing depended
on whether the stimulus was emotional. - For neutral images, greater response to
scenes that were remembered in detail
versus scenes that the participant just had a
familiarity with - For emotional images, there was no
difference between remember vs know
Amygdala: Emotion and Retrieval
- Effect of remembering vs knowing depended
on whether the stimulus was emotional. - For emotional images, greater response to
scenes that were remembered in detail
versus scenes that the participant just had a
familiarity with - For neutral images, there was no difference
between remember vs know
Emotional memories are no more accurate in details later,
despite a high confidence
- Task: study negative and neutral pictures, sometimes
surrounded by a red frame. Later, ask participants whether
they remember having seen the frame. - Participants subjectively ’remember’ more, but actually are
worse for the peripheral frame detail
Summary: Emotion and Memory
* Encoding
* Storage (consolidation)
* Retrieval
Emotion affects encoding by capturing our attention and
improving perception
* Evidence:
* The Emotional Attentional Blink
* Visual perception enhancement experiment
- Emotion prevents memories from being forgotten because of
interactions between the amygdala and the hippocampus - Evidence:
- Emotional and non-emotional stimulus forgetting
Independent neural systems underlie the subjective sense of
remembering for emotional and neutral scenes
* Amygdala responds more to remembered emotional scenes than
just known emotional scenes
* Parahippocampus responses more to remembered neutral scenes
than just known neutral scenes.
Fear conditioning
- A form of classical conditioning in which a neutral stimulus
(e.g., light) acquires aversive properties by virtue of being
paired with an aversive event (e.g., shock)
Effect of amygdala lesions on fear conditioning
- After a lesion to the amygdala, fear can still be experienced in
relation to harmful stimuli, but fear conditioning is impaired - Lesions to rat amygdala do not affect natural response to fearinducing stimuli (will still startle in response to shock or loud
noise) - Fear expression is intact
- Lesions to rat amygdala prevent learning of the conditioned
startle response (e.g., won’t startle from light alone) - Impaired fear conditioning
Fear conditioning: Amygdala circuit
ln to cn to brainstem/hypothalamus
Fear Conditioning via Social Learning
Humans don’t always need to directly experience negative
events themselves to associate certain aspects of the
environment with danger
* e.g., We learn about germs and fear them without direct perception of
them
* You can tell a person that a stimulus will be associated with
pain, and that stimulus with activate the amygdala on its own
* Same thing happens when you see someone else get shocked after
they see a specific cue
Extinction of Fear Conditioning
Extinction: After repeated presentation of CS (light) without
US (shock), CS alone no longer causes a fear response
* Spontaneous recovery: Fear response can return the next day
though – tells us that memory hasn’t been “erased”
* During extinction, the vmPFC communicates with the lateral
nucleus to inhibit the fear memory
Spontaneous recovery
Fear response can return the next day
though – tells us that memory hasn’t been “erased”
- There are multiple sensory pathways to the amygdala:
- “Slow road” or “High road”: sensory stimuli are relayed through the
thalamus to the cortex where they are processed before information
is relayed to the amygdala
- “Slow road” or “High road”: sensory stimuli are relayed through the
- “Fast road” or “Low road”: sensory stimuli are directly relayed from
thalamus to the amygdala
- “Fast road” or “Low road”: sensory stimuli are directly relayed from
evidence of slow/fast pathways of amygdala
Amygdala is activated by fearful expressions in a blindsight patient
with damage to primary visual cortex who is not consciously aware of
the stimulus
* Amygdala is activated by fearful expressions in healthy participants
when images are masked so the participants is not consciously aware
of seeing them
What are the key distinctions between the basic (core)
emotions approach versus the dimensional emotions
approach?
People all of the world show pretty much the same facial
expressions for 6 basic emotions:
Anger, happiness, disgust, surprise, sadness, fear
Ekman’s “Universal Facial Expressions”
- What the basic emotions approach propose?
- Alternative framework to discrete, “basic emotions”
approach
- How do people study the basic emotions approach? Name
evidence that seems to support the basic emotions approach.
- People in Papua New Guinea, don’t watch TV or read magazines
What does the dimensions of emotion approach propose?
What are the two dimensions?
- Emotions tap into a “core affect” system and are
CONSTRUCTED as reactions to events along continuous
dimensions - Example:
VALENCE (negative – positive)
vs.
AROUSAL (low – high)
- Briefly describe circuitry of the amygdala, and why
lesions to the amygdala obliterate fear conditioning
LN projects to central nucleus (CN), which is connected to parasympathetic and
sympathetic nervous systems (to activate an emotional response) in hypothalamus and brainstem
Describe the 2 pathways to the amygdala and what
each pathway is good for.
- There are multiple sensory pathways to the amygdala:
- “Slow road” or “High road”: sensory stimuli are relayed through the
thalamus to the cortex where they are processed before information
is relayed to the amygdala
- “Slow road” or “High road”: sensory stimuli are relayed through the
- “Fast road” or “Low road”: sensory stimuli are directly relayed from
thalamus to the amygdala
- “Fast road” or “Low road”: sensory stimuli are directly relayed from
patient SM
Although clinical observations suggest that humans with
amygdala damage have abnormal fear reactions and
a reduced experience of fear [1–3], these impressions have
not been systematically investigated. To address this gap,
we conducted a new study in a rare human patient, SM,
who has focal bilateral amygdala lesions [4]. To provoke
fear in SM, we exposed her to live snakes and spiders,
took her on a tour of a haunted house, and showed her
emotionally evocative films. On no occasion did SM exhibit
fear, and she never endorsed feeling more than minimal
levels of fear. Likewise, across a large battery of self-report
questionnaires, 3 months of real-life experience sampling,
and a life history replete with traumatic events, SM repeatedly demonstrated an absence of overt fear manifestations
and an overall impoverished experience of fear. Despite
her lack of fear, SM is able to exhibit other basic emotions
and experience the respective feelings. The findings support
the conclusion that the human amygdala plays a pivotal role
in triggering a state of fear and that the absence of such
a state precludes the experience of fear itself.
The disconnection
between SM’s verbally stated aversion to snakes and spiders
and her actual real-life behavior was striking. She did not
display any signs of avoidance, but instead exhibited an
excessive degree of approach (a pattern highly reminiscent
of the behavior in monkeys with Kluver-Bucy syndrome [12]).
