Epigenetics

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Chapter 8 endnote 33, from How Emotions are Made: The Secret Life of the Brain by Lisa Feldman Barrett.
Some context is:

The human brain is itself a cultural artifact because it is wired by experience. We have genes that are turned on and off by the environment, and other genes that regulate how sensitive to the environment we are.

Chapter 10 endnote 28 & 33, from How Emotions are Made: The Secret Life of the Brain by Lisa Feldman Barrett.
Some context is:

[note 28] [Depression is] classified as a disorder of affect and often blamed on negative thinking: You’re too hard on yourself, or have too many self-defeating, catastrophic thoughts. Or perhaps traumatic events trigger depression, particularly if your genes make you vulnerable.


[note 33] Your genes could leave you sensitive to your environment and every little problem.

If we abandon a poorly informed and superficial treatment of genetics,[1][2] we learn that the genome changes under the influence of the environment. Genes are turned on and off by the world, and there are other genes that determine how sensitive we are to the world in the first place. So genes guide brain wiring, but do not fully determine it on their own like a preformation program.[3]

Here are two creative lines of research of potential interest:

  1. Neuroscientists Huda Akil and her husband Stanley Watson started with rats that either explored a novel environment or remained close to a wall. Then they in-bred the rats. After over 40 generations, they had created a strain of novelty-seeking animals who are not bothered by uncertainty, and they look resilient to developing behavioral analogs to anxiety and depression. The other more restricted animals are not resilient.[4][5]  The very cool thing is that if you give the rats a treatment to change their gene expression, just once while they are babies, and then test them as adults, you can make the restricted rats look more resilient.[6] This reminds me of research by the psychologist Jerome Kagan on children with inhibited vs. non-inhibited temperaments.
  2. There is also the "orchid hypothesis."[7][8] Orchids do fabulously in enriched environments (like a greenhouse) but put them in the cold and they die. A dandelion can grow just about anywhere. And so it is with children. Dandelion children are resilient. They grow and develop fine just about anywhere. To them, the entire world is a patch of soil.  Orchid children, on the other hand, flourish in an enriched environment, and falter in an impoverished one. The short allele of the 5HTT serotonin transporter gene (that has been linked to stress and mental illness) is a genetic variant that contributes to orchids (vs. dandelions).[9]


Notes on the Notes

  1. Charney, Evan. 2012. "Behavior genetics and postgenomics." Behavioral and Brain Sciences 35 (5): 331-358.
  2. Turkheimer, Eric, Erik Pettersson, and Erin E. Horn. 2014. "A phenotypic null hypothesis for the genetics of personality." Annual Review of Psychology 65: 515-540.
  3. Lewontin, Richard. 2002. The Triple Helix: Gene, Organism, and Environment. Cambridge, Massachusetts: Harvard University Press.
  4. Clinton. Sarah, Sue Miller, Stanley J. Watson, and Huda Akil. 2008. "Prenatal stress does not alter innate novelty-seeking behavioral traits, but differentially affects individual differences in neuroendocrine stress responsivity." Psychoneuroendocrinology 33(2): 162-177.
  5. Chaudhury, Sraboni, Elyse L. Aurbach, Vikram Sharma, Peter Blandino, Cortney A. Turner, Stanley J. Watson, and Huda Akil. 2014. "FGF2 is a target and a trigger of epigenetic mechanisms associated with differences in emotionality: Partnership with H3K9me3." Proceedings of the National Academy of Sciences 111 (32): 11834-11839.
  6. Litvin, Yoav, Cortney A. Turner, Mariel B. Riosa, Pamela M. Maras, Sraboni Chaudhury, Miriam R. Bakera, Peter Blandino, Jr., Stanley J. Watson, Jr., Huda Akil, and Bruce McEwen. 2016. "Fibroblast growth factor 2 alters the oxytocin receptor in a developmental model of anxiety-like behavior in male rat pups." Hormones and Behavior 86: 64-70.
  7. Boyce, W. Thomas, and Bruce J. Ellis. 2005. "Biological sensitivity to context: I. An evolutionary-developmental theory of the origins and functions of stress reactivity." Development & Psychopathology 17 (2): 271–301.
  8. Ellis, Bruce J., and W. Thomas Boyce. 2008. “Biological Sensitivity to Context.” Current Directions in Psychological Science 17 (3): 183–187.
  9. Conley, Dalton, Emily Rauscher and Mark L. Siegal. 2013. "Beyond orchids and dandelions: Testing the 5HTT 'risky' allele for evidence of phenotypic capacitance and frequency dependent selection." Biodemography and Social Biology 59 (1): 37-56.