Upload
bennett-harrison
View
222
Download
0
Tags:
Embed Size (px)
Citation preview
Affective Neuroscience
Leah Somerville, PhD
Sackler Institute for Developmental Psychobiology
Weill Medical College of Cornell University
What is emotion?
• “one of the most significant things ever said about emotion may be that everyone knows what it is until they are asked to define it”– Joseph LeDoux (1996)
What is emotion?• Emotion = reflects a kind of motion outward• An inferred complex sequence of reactions to a
stimulus including cognitive evaluations, subjective changes, autonomic and neural arousal, impulses to action, and behavior designed to have an effect (functional) upon the stimulus that initiated the complex sequence (Plutchik, 1982)
– Inferred– Reaction– Functional– ***Cognitive appraisal, feeling, and action***
Today’s agenda
1. What are emotions and do they have a purpose?
2. How does we study emotions in the laboratory?
3. What brain circuits support emotional processes?
4. How does emotion go awry in psychiatric conditions?
What are emotions and do they have a purpose?
A brief History of Affective Neuroscience
• The Expression of the Emotions in Man and Animal, Charles Darwin (1872)– Emotions are similar across species and cultures.
James-Lange Theory of emotion (late 1800s)
Physiology Appraisal
“My heart is pounding, so I must be afraid.”
Cannon-Bard Theory of emotion(1920s)
Appraisal Physiology
“I feel afraid, so my heart pounds.”
Where these theories fall short
• J-L: Assumes there is a unique physiological signature to each emotion.
• C-B: Physiological responses are generated so quickly, it’s unlikely that we could have perceived the emotion first.
Schachter Two Factor Theory(Schachter and Singer, 1962)
Physiology + Context Feeling and action
Schachter & Singer’s classic study
• Shot of adrenaline to participants– Explained as having arousing
side effects or not mentioned• Placed in room with happy or angry
confederate• Participants with no explanation for
arousal experienced happiness or anger
There is still debate about what an emotion “is”, but nowadays it is agreed on that it involves interactions
between physiology, feeling, and context.
Adaptive purpose of emotions• Emotions induce motivation
Spring us into action
Lower sensory thresholds
Facilitates learning- enhance memory- modulates appropriate
approach/avoidance behavior- the arousal associated with
emotions facilitates performance (to a certain extent)
Yerkes-Dodson law
How do we study emotions?
Affective Neuroscience Toolbox
• Animal models (especially fear)• Lesion studies• Psychophysiology
– Heart Rate– Skin conductance (ANS arousal)
• Neuroimaging:– fMRI (Hemodynamic response)
• Various other electrophysiologytechniques
– Electroencaphalography– Magnetoencephalography– Single unit recordings– Transcranial magnetic stimulation
How to study emotion in the lab?• Tapping into emotional experiences and perception
– Make people emotional in the lab– Mood inductions– Paradigms that induce fear or anxiety (threat-of-shock) or other
emotions (displaying evocative imagery)– Measure responses to emotional cues (facial expressions)
• Tapping into emotional regulation and the outcome of experiencing emotion– Induce emotion measure subjects’ ability to dampen– Measure how emotions facilitate secondary behaviors (memory,
action)
• Directly test individuals who experience emotional dysregulation– Psychiatric illnesses involving fear, anxiety, depression
Understanding the neurobiology of emotions
Dalgleish, 2004
Functional Neuroanatomy of Emotion
Nucleus Accumbens
Prefrontal Cortex
Dorsomedial
Orbital
Hypothalamus
Ventral Pallidum
Amygdala
Anterior Cingulate
Appraisal
Experience
Action
The Amygdala
The amygdalae are almond shapes bodies located in bilateral medial temporal lobe.
Amygdala
Hippocampus
© BrainConnection.com
Klüver-Bucy Syndrome (1939)• Bilateral removal of temporal cortex in monkeys.• Drastic Change in behavior:
– Loss of emotional reactivity,
– Hypersexuality,
– Orality,
– Disrupted social behavior,
– Falling in social standing.
• Weiskrantz (1956) bilateral lesions of amygdala produced similar behavioral changes.
• Improved methods (ibotenic acid lesions) showed that central site is amygdala (e.g. Murray et al., Behavioral Neuroscience, 1996)
Pavlovian ConditioningConditioned Stimulus (CS)
Unconditioned Stimulus (US)
Conditioned Response
Fear Conditioning
Ledoux, 1995
Defensive BehaviorANS arousalHypoalgesiaReflex potentiationStress hormones
Auditory fear
conditioning
Phelps and Ledoux, 2005
Information about the CS is integrated with information about the US within the amygdala.
Fear conditioning in humans
LaBar et al., 1998
+
Insights on the role of the amygdala in appraising
emotions from Patient SM
S. M.
Insights on the role of the amygdala in appraising
emotions from Patient SM
Adolphs et al. 1994
Adolphs et al., 1995
• Subject with bilateral amygdala lesions was asked to draw facial expressions of emotions.
Amygdala lesions disrupt physiological responding to conditioned cues in humans
Labar et al., 1998
Processing emotional cues in the environment
Something really bad is going on near us, and you’d do well to find out what I know
Amygdala and healthy adults• Amygdala responses to fearful faces in normal humans (Breiter
et al., 1996).
•(Breiter et al., 1996)
Rapid processing in humans
Copyright ©1998 Society for Neuroscience
Whalen, P. J. et al. J. Neurosci. 1998;18:411-418
33 (17) msec
Whalen et al., 2004
Amygdala response habituates
Breiter et al., 1996
However, the role of the amygdala in emotion
processing is even more complicated than we thought
Resolving emotional ambiguity
Facilitating learning
What conclusions can we draw about the role of the amygdala in
emotional processing?• An intact amygdala is necessary for the
acquisition and expression of fear (animal, lesion patients)
• In humans, the amygdala carries the more general role of detecting and learning about important information in the environment.– motivational salience account
AppraisalExperience
Action
Emotions serve an important function, but we also need to be
able to put on the brakes.
On the Inside
On the outside
Emotion regulation
• The capacity to modify an emotional experience
– 2 examples• Fear extinction• Active reappraisal
Dalgleish, 2004
Functional Neuroanatomy of Emotion
Nucleus Accumbens
Prefrontal Cortex
Dorsomedial
Orbital
Hypothalamus
Ventral Pallidum
Amygdala
Anterior Cingulate
Fear extinction
Conditioned Response
Fear extinction
Extinction and the MPFC
• The ventromedial prefrontal cortex is critical to emotion regulation
• Enables new learning of a
positive interpretation of the
once-negative stimulus• Dampens amygdala response
via direct inhibitory gating• Behavior: no response to
previous fear cue
Animal findings
Milad & Quirk, 2002
Lesions to rodent infralimbic cortex prevent the retention of extinction memories
Human findings
VMPFC recruitment facilitates retention of extinction memory
VMPFC and regulation of reward approach
Bechara et al., 2005
Behavioral Results(Bechara et al., 1999)
$100 wins
$50 wins
Skin Conductance Results (Bechara et al., 1999)
Results• Healthy control participants developed:
– “Hunches” about how to maximize wins.– Showed elevated SCR responses in anticipation of
outcomes after poor choices.
• Patients with ventromedial PFC damage:– Performed poorly on task (risky/low payoff
choices).• Did not maximize wins and losses.
– Did not show elevated SCR responses after poor choices.
Kim et al., 2003
Kim et al., 2003
Emotion regulation via Cognitive ReappraisalOchsner et al., 2002; 2004
Ochsner et al., 2002
Amygdala activity modulated by regulation strategy
Ochsner et al., 2004
The story isn’t so simple – VMPFC may also be involved in reappraisal
• Other studies have used similar paradigms to show the VMPFC engaged while actively downregulating emotion
• Extinction == learning a new interpretation of a previously aversive cue
• Reappraisal == using cognitive strategies to actively ‘spin’ a new interpretation of a previously aversive cue
VMPFC
VMPFC, VLPFC
Emotions & Psychopathology
• The symptoms of many psychiatric illnesses involve inappropriate emotional responses and/or ineffective emotion regulation
PTSD, phobias : Hyperresponsive emotional appraisal? Failure to extinguish?
Depression : Failure to reappraise?
This field is still a work-in-progress!
Anxiety disorders and engagement of emotion circuitry
Meta-analysis Etkin & Wager, 2007
PTSD: failure to extinguish?
Summary by Milad et al., 2006
PTSD: Hyper-responsiveamygdala
Hypo-responsiveVMPFC
Depression: failure to reappraise?
Johnstone et al., 2008
Take-home points• Emotions are complex reactions involving feelings, physiological
reactions, and contextual interpretations.
• The generation and experience of emotion is primarily modulated through interactions between subcortical and cortical brain structures including the amygdala and subregions of the prefrontal cortex.
• The amygdala plays a critical role in emotional learning and generating appropriate responses to environmental cues.
• The VMPFC and VLPFC interact with subcortical structures like the amygdala to modulate emotional responses.
• Dysfunctional subcortical-cortical interactions play an important role in the pathophysiology of many psychiatric illnesses.