2017-10-23 11:18:00

Don't You Worry 'Bout a Thing

Today's Topics

  • Happiness, pleasure, and the reward system
  • Fear & stress
  • Quiz 3 Friday

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
  • 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 opioids (endorphins)
  • Endogenous cannabinoids

ACh projections in the CNS

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.

The neuroscience of fear and stress

Inducing "fear-like" behavior in animals

Rat vs. Human

Your thoughts: Can we use an animal model to study 'emotion'?

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

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 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 stress ain't like mine

  • Phasic (short-term) vs. Chronic (long-term)
  • Physical stress (hunger, thirst, injury, disease) vs. social stress

Main points

  • Biological approach to emotion
    • Behavior
    • Physiological states
    • Subjective feelings
    • Adaptive function
  • Networks of brain systems, multiple NT systems

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.

Cock, Valérie Cochen De, Marie Vidailhet, and Isabelle Arnulf. 2008. “Sleep Disturbances in Patients with Parkinsonism.” Nature Clinical Practice Neurology 4 (5): 254–66. doi:10.1038/ncpneuro0775.

Davis, Michael. 1992. “The Role of the Amygdala in Fear-Potentiated Startle: Implications for Animal Models of Anxiety.” Trends in Pharmacological Sciences 13. Elsevier: 35–41. doi:10.1016/0165-6147(92)90014-W.

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.

Flores, África, Rafael Maldonado, and Fernando Berrendero. 2013. “Cannabinoid-Hypocretin Cross-Talk in the Central Nervous System: What We Know so Far.” Neuropharmacology 7: 256. doi:10.3389/fnins.2013.00256.

Heath, Robert G. 1963. “Electrical Self-Stimulation of the Brain in Man.” American Journal of Psychiatry 120 (6). Am Psychiatric Assoc: 571–77. doi:10.1176/ajp.120.6.571.

Kohls, Gregor, Coralie Chevallier, Vanessa Troiani, and Robert T Schultz. 2012. “Social ‘Wanting’dysfunction in Autism: Neurobiological Underpinnings and Treatment Implications.” Journal of Neurodevelopmental Disorders 4 (10). BioMed Central Ltd: 1–20. doi:10.1186/1866-1955-4-10.

Kringelbach, Morten L, and Kent C Berridge. 2009. “Towards a Functional Neuroanatomy of Pleasure and Happiness.” Trends in Cognitive Sciences 13 (11). Elsevier: 479–87.

LeDoux, Joseph. 2012. “Rethinking the Emotional Brain.” Neuron 73 (4): 653–76. doi:10.1016/j.neuron.2012.02.004.

McEwen, B. S. 2007. “Physiology and Neurobiology of Stress and Adaptation: Central Role of the Brain.” Physiological Reviews 87 (3): 873–904. doi:10.1152/physrev.00041.2006.

Medina, Javier F, J Christopher Repa, Michael D Mauk, and Joseph E LeDoux. 2002. “Parallels Between Cerebellum-and Amygdala-Dependent Conditioning.” Nature Reviews Neuroscience 3 (2). Nature Publishing Group: 122–31. doi:10.1038/nrn728.

Milner, Peter M. 1989. “The Discovery of Self-Stimulation and Other Stories.” Neuroscience & Biobehavioral Reviews, The Neural Basis of Reward and Reinforcement: A Conference in Honour of Peter M. Milner, 13 (2–3): 61–67. doi:10.1016/S0149-7634(89)80013-2.

Nestler, Eric J, and William A Carlezon. 2006. “The Mesolimbic Dopamine Reward Circuit in Depression.” Biological Psychiatry 59 (12). Elsevier: 1151–9. doi:10.1016/j.biopsych.2005.09.018.

Pessoa, Luiz. 2008. “On the Relationship Between Emotion and Cognition.” Nature Reviews Neuroscience 9 (2): 148–58. doi:10.1038/nrn2317.

Sapolsky, Robert M. 2016. “Psychiatric Distress in Animals Versus Animal Models of Psychiatric Distress.” Nature Neuroscience 19 (11): 1387–9. doi:10.1038/nn.4397.