2:25
- Biological approach to emotion
- Behavior
- Physiological states
- Subjective feelings
- Adaptive function
- Networks of brain systems, multiple NT systems
2019-03-20 14:28:00
Don't You Worry 'Bout a Thing
Today's Topics
- Quiz 3; Exam 2 review on Thursday
- Biology of emotion
- Happiness/pleasure and reward
- Fear & stress
Biology of Emotion
- What is emotion?
- What are the types of emotions?
- Biological systems involved in emotion
What is emotion?
- Feelings
- Physiological state
- Actions (now)
- Propensity to act (in the future)
What is cause? What is effect?
"Do we run from a bear because we are afraid or are we afraid because we run? William James posed this question more than a century ago, yet the notion that afferent visceral signals are essential for the unique experiences of distinct emotions remains a key unresolved question at the heart of emotional neuroscience."
Competing views
- James-Lange
- Physiological response -> subjective feelings
- Cannon-Bard
- Severing CNS (spinal cord & vagus) from rest of body leaves emotional expression unchanged
- Physiological states slow, don't differentiate among emotions
Competing views
- Schacter-Singer
- Physiological arousal + cognitive appraisal -> emotional states
What are the different types of emotions?
Emotions
- Vary in
valence
- Positive/negative
- Vary in intensity (arousal)
- Vary in
action tendency
- Approach/avoid
Emotions (can) serve biological goals
- Ingestion
- Defense
Reproduction
Affiliation
Plutchik
Is emotion different from cognition?
(Swanson 2012)
Is emotion different from cognition?
(Pessoa 2008)
Here, I will argue that complex cognitive–emotional behaviours have their basis in dynamic coalitions of networks of brain areas, none of which should be conceptualized as specifically affective or cognitive. Central to cognitive–emotional interactions are brain areas with a high degree of connectivity, called hubs, which are critical for regulating the flow and integration of information between regions.
(Pessoa 2008)
Here, I will argue that complex cognitive–emotional behaviours have their basis in dynamic coalitions of networks of brain areas, none of which should be conceptualized as specifically affective or cognitive. Central to cognitive–emotional interactions are brain areas with a high degree of connectivity, called hubs, which are critical for regulating the flow and integration of information between regions.
Emotion as "computing" (or information processing)
- Input
- Internal states
- External world
- Processing/evaluation
- Output
- Internal states
- External world
Happiness and reward
Components of happiness
- Aristotle
- Hedonia
- Pleasure
- Eudaimonia
- Life satisfaction
- Relates to motivation
"Computing" happiness
- Inputs
- External
- Internal
- Processing
- Outputs
- Feelings
- Actions
Brain mechanisms
- Circuits for signaling pleasure and pain
- Similarities across animal species
- Behavior & brain
- Dopamine and endogenous opioid neurotransmitter systems involved
Neuroanatomy of 'happiness'
Rewards
- A reward reinforces (makes more prevalent/probable) some behavior
- Milner and Olds (Milner 1989) discovered 'rewarding' power of electrical self-stimulation
- (Heath 1963) studied effects in human patients.
Electrical self-stimulation
"Reward" circuitry in the brain
Nodes in the "reward" circuit
- Ventral tegmental area (VTA) in midbrain
- Nucleus accumbens (nAcc), ventral striatum
- Hypothalamus (Hyp)
- Amygdala (Amy)
- Hippocampus (HP)
- Dorsal Raphe Nucleus/Locus Coeruleus (DR/LC)
- Prefrontal cortex (PFC)
Nucleus accumbens and dorsal striatum
Psychopharmacology of 'happiness'
- Dopamine
- Opioids
- Cannabinoids
- Serotonin, Norepinephrine
- ACh
Endogenous morphine-like NTs (endorphins) from hyp, NST
Endogenous cannabinoid system
- Cannabinoids == psychoactive compounds found in cannibis
- Cannabinoid receptors, CB1 in CNS; CB2 in body, immune system
Brain contains its own systems for binding drugs associated with 'pleasure'
- Endogenous morphine-like compounds (endorphins)
- Morphine an opioid
- Endogenous cannabinoids, too
Generalizations about happiness/pleasure
- Types of pleasure activate overlapping areas
- Pleasure/happiness engage a network of brain areas
- Pleasure/happiness signaling involves multiple neuromodulators, but DA especially important
- “Reward” pathways activated by many different inputs
Fear and stress
Inducing "fear-like" behavior in animals
Rat vs. Human
Adapted from (Davis 1992)
Amygdala circuits
Amygdala's inputs
- Convergent inputs
- Thalamus ("direct" or "fast"")
- Cerebral cortex ("indirect" or "slow")
Amygdala's outputs
- Project to
- CG (central gray matter) of tegmentum: behavior
- LH (lateral hyp): ANS
- PVN (paraventricular n. of hyp): hormones
- Fast-acting, involuntary responses
- Lesions of amygdala impair 'fear conditioning'
Cerebral cortex role
- Response discrimination?
- Cortex lesions cause generalized not cue-specific fear response
- Fast, crude responses vs. slower, detailed ones
- That’s a stick, not a snake!
- Prefrontal cortex and response inhibition
But, are we really studying learned 'fear'?
- Amygdala connected to other 'affective' nodes in neural network
- Emotion not just about subjective feelings
Amygdala as processing hub
Amygdala as key hub in circuit for survival
Emotion as global physiological/behavioral "state"
"Emotional" stimuli serve multiple roles
Stress
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Stressors linked with biological imperatives
- Sustenance
- Hunger, thirst
- Well-being/defense
- Threat
Stressors linked with biological imperatives
- Reproduction
- Rejection
- Affiliation
- Loneliness
Stress and the brain
Brain under stress
- Acute stress
- Short duration
- Fast action required
- HPA (Cortisol), SAM (NE/Epi) axes
- Brain detects threat
- Mobilizes physiological, behavioral responses
Brain under stress
- vs. Chronic stress
- Long duration, persistent
Glucocorticoids
- Adrenal cortex releases hormones
- Cortisol (hydrocortisone)
- Increases blood glucose levels
- Suppresses immune system
- Reduces inflammation
- Aids in metabolism
- Receptors in brain and body
- Cortisol (hydrocortisone)
Cortisol and the brain
Glucocorticoid cascade hypothesis
- Cort receptors in hippocampus, amygdala, hypothalamus
- Hippocampus regulates HPA axis via hypothalamus
- Prolonged cortisol exposure reduces hippocampus response
- Reduces volume, connectivity in hippocampus
- Hip critical for long-term memory formation
- Chronic stress impairs long-term memory
But, cortisol -> stress link not straightforward
Stress and coping across the animal kingdom
- Pain thresholds lower (sensitivity greater) when a mouse's cage mate is also in pain
- Rats will cooperate to release distressed cage mage, foregoing food rewards
- (Sapolsky 2016)
Why Zebras Don't Get Ulcers
Your (zebra) stress ain't like mine
- Phasic (short-term) vs. chronic (long-term)
- Physical stress (hunger, thirst, injury, disease) vs. social stress
Main points
Next time
- Quiz 3
- Review Exam 2
References
Clapp, Peter, Sanjiv V. Bhave, and Paula L. Hoffman. n.d. “How Adaptation of the Brain to Alcohol Leads to Dependence.” http://pubs.niaaa.nih.gov/publications/arh314/310-339.htm.
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Faresjö, Åshild, Elvar Theodorsson, Marios Chatziarzenis, Vasiliki Sapouna, Hans-Peter Claesson, Jenny Koppner, and Tomas Faresjö. 2013. “Higher Perceived Stress but Lower Cortisol Levels Found Among Young Greek Adults Living in a Stressful Social Environment in Comparison with Swedish Young Adults.” PLoS ONE 8 (9): e73828. doi:10.1371/journal.pone.0073828.
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