Posts Tagged ‘Genetics’


March 6, 2020

This post is based on portions of a book, Resilience: The Science of Mastering Life’s Greatest Challenges by by Steven Southwick and Dennis Charney. A common question that arises when discussing many topics is the nature nurture issue. That is how much of a person is determined by that person’s genes and how much by the environment. That is a naive question that is difficult to answer for two reasons. One is that there is natural confound here, and that is how to distinguish the effects of genetics and the environment. IQ measurements can be separated mathematically into a genetic component and an environmental component. Although this can be done mathematically it cannot be done empirically as these two components are confounded.
There is a true anecdote illustrating this confound. It tells of two sisters who are identical twins, yet one is academically and socially successful, whereas the other has the autistic spectrum disorder.

Epigenetics is the study of how genes are read out or expressed. It matters not if you have fantastic genes, but the information in these genes is not manifested. A variety of internal and external environmental events, such as stress, social support, and fear, can trigger biochemical reactions, such as methylation, that then turns genes on or of. Moreover, these processes are dynamic and potentially reversible. So when a gene is “turned on” it directs the making of gene products, such as proteins. But, when a gene is “turned off” these gene products are no longer produced.

Zang has conducted studies showing that if a mother rat provides only low levels of licking and grooming to her pups, which is analogous to neglectful parenting in the rat world, the pub will exhibit increased susceptibility to stress throughout their lives. But attentive maternal care, as reflected by high levels of licking and grooming, can contribute to later stress resilience. These effects of maternal licking and grooming appear to be mediated, at least in part, by epigenetic changes in gene expression. Research conducted in Michael Meaney’s laboratory has shown that variations in maternal care have been associated with variations in expression of glucocorticoid receptors and hippocampal sensitivity to stress. According to Nestler, similar epigenetic effects of maternal care, as well as other lifetime experiences, on later vulnerability or resilience to stress are likely to “hold up in humans.”

The authors write, “A variety of environmental events, including stress, social interactions, and drug use, can cause epigenetic changes in gene expression. Although much remains to be learned, the rapidly expanding field of epigenetics may soon help us to better understand the origins of stress vulnerability and discover ways to manage it. It may also help us to better understand resilience and the mechanisms by which training can enhance factors associated with resilience (e e.g. exercise, social support, cognitive reframing). And as noted by psychopharmacologist Steven Stahl, “psychotherapy can now be conceptualized not only by its classic psychodynamic principles, but also indeed as a neurological problem capable of inducing epigenetic changes in brain circuits, not unlike the ultimate actions of psychotropic drugs.”

The Epigenetics Revolution

October 20, 2016

The title of this post is identical to the title  of a book by Nessa Carey.  The Subtitle is How Modern Biology is Rewriting Our Understanding of Genetics, Disease, and Inheritance.  The research has shown how naive the nature nurture distinction was and how wrong headed was IQ research that estimated numerical contributions of genes and environment to IQ.  Presumably the immediately preceding post has disabused you of those issues.  But Flynn does not specifically mention how epigenetics further muddies any distinction.

Epigenetics refers to how information is read out of our genes.  Carey tries to make the topic easy, but it is a very complicated topic.  It is better to have the modest goal of understanding the ramifications of the topic.

Even identical (monozygotic) twins can vary.  A television program presented the case of two identical twin sisters.  One was quite successful both academically and socially.  The other was autistic.  To be sure, such extreme cases are exceedingly rare, but the differences between identical twins increase as they age.  Much of this can be attributed to errors in the readout from the genes.  But childhood experiences can affect this readout.

Go to the healthy memory blog post “Turning on Genes in the Brain” to learn how adverse childhood experiences can cripple a child psychologically for life and lead to drug addiction and criminal behavior.  Moreover, the negative changes in the DNA of the child can be passed on to her children.

However, good habits and good experiences can lead to beneficial epigenetic experiences.  There is a series of healthy memory blog posts on how meditation can produce these changes.  First go to the post “An Update of the Relaxation Response Update. Then ago to the next in the series, “The Genetic Breakthrough—Your Ultimate Mind-Body Connection.”  Then go to “Cancer and the Genetic Horizons on the Mind
Body Treatment.”  Then go to “Cognitive Benefits of the Relaxation Response and Mindfulness.”  You might also want to review “The Two Step Process,” and for some personal tips on meditation, “Personal Tips on Meditation Techniques In General and the Relaxation Response in Particular.”

© Douglas Griffith and, 2016. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and with appropriate and specific direction to the original content.

Does Your Family Make You Smarter?

October 18, 2016

The title of this post is identical to the title of a very important book by Professor James R. Flynn.  The subtitle is ”Nature, Nurture, and Human Autonomy.”  Flynn is the founder of the “Flynn Effect,” which describes the inflation of the Intelligence Quotient (IQ) over time.  This effect has been so large and consistent that the IQ has to have been periodically updated and recalibrate so that the mean would be 100.  Flynn had argued that this must be an artifact as we apparently had not become as smarter as the recalibration of the test indicated.  However, further research and collaboration with his colleague W. T. Dickens led to the conclusion that we were becoming smarter, and an explanation of how we were becoming smarter.

“Does Your Family Make You Smarter” is highly technical.  For those whose area of interest is this topic, then reading is mandatory.  However, this book should be of interest to everyone, so HM shall try to summarize the salient points that are of general interest.

Historically, IQ has been a hot topic with respect to the distinction between genetic and environmental effects.  Although we can distinguish between the two factors with mathematics, it is important to realize that in the real world we cannot view genetic as distinct from environment effects.  HM is reminded of a story, perhaps apocryphal, of an experiment that was done to determine what was the true language for humans.  So the plan was not to interact or speak with a newborn baby.  They thought that when the baby did speak, they would know what the true human language was.  Of course, in this environment the baby would never learn a language and would be severely handicapped.

The truth is that the effects of genes and environment are inextricably intertwined.   Flynn does not even touch the topic of epigenetics, which refers to the information that is read out from the genes.  Recent research has found that the nature of this readout can be beneficial or detrimental depending on the nature of the environment.

Flynn’s colleague Dickens posited that genes and environment become more highly correlated as we age, meaning that their influence was additive.  The potency of the environment was based by combining the two, which erroneously had been ascribed to genes alone in the twin studies.  By the time we reach maturity, current environment has only a feeble memory of past environments except under unusual  circumstances such as brain trauma.

What has been happening is that modernity is causing our habits of processing information to adapt so that we can more readily handle abstract concepts. So most of us have become more intelligent.  There is a social multiplier effect, which is aided and abetted by technology.  The example provided is basketball.  The televising of basketball games enabled everyone to see how the game was played by experts.  Young players try to model on the playground what they saw on television.

There are adverse effects of new technology, such as the spread of misinformation.  But there are also good effects as better ways of thinking and doing things can be readily communicated.

Flynn speaks of family effects.  Family effects include genes and the environment provided by the family.  A family of professionals will have a higher level of communication and will follow more media with better quality information.  These effects continue until the young adult leaves home.  Intelligence should continue to develop depending upon the environments in which she works and plays.  In good environments intelligence should continue to grow.  This growth can stop when people retire unless they continue to foster their cognitive development with mental and social activities that promote continued growth.

Healthy memory readers should immediately recognize that this is in consonance with the message that is repeated over and over in this blog.  Should you not have recognized this consonance, then you have a lot of remedial reading to do.  Start by entering “growth mindsets” into the search block of the healthy memory blog.

Dr. Flynn is 82 years old and provides an ideal individual to try to emulate.

© Douglas Griffith and, 2016. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and with appropriate and specific direction to the original content.

Nature vs. Nurture: Genetics, Environment, and Cognition

June 17, 2014

This is the title of Chapter 12 in Greenwood and Parasuman’s Nurturing the Older Brain and Mind. They begin the chapter with a quote from Rene Dubos, So Human an Animal. “Genetics and experiential factors shape the biological and behavioral manifestations of human life, but they do not suffice to account for the totatality of human nature. Man also enjoys a great degree of freedom in making decisions; he is par excellence the creature that can choose, eliminate, organize, and thereby create.”

It is unfortunate but all too often the nature vs nurture issue is regarded as a deterministic dichotomy. Behavioral geneticists have done studies, identical twins have been frequently used, to estimate topics such as how much is IQ determined by genetics and how much is determined by the environment. What these studies neglect is the interaction between genetics and the environment. Neither exists in isolation from the other. Behavior and performance are the result of the interaction between genes and the environment.

Fortunately molecular genetics provides an alternative approach to behavioral genetics. The molecular approach allows for the study of specific genes and their alleles. This research has found that a particular allele of the apolipoprotein E (APOE) gene is a major risk factor for the development of Alzheimer’s. Pay attention to the term “risk factor.” Rather than causing Alzheimer’s this particular allele increases the risk of suffering from the disease. Moreover, it is possible that age-related cognitive decline may occur only in those who possess one or two copies of this allele. It is estimated that this could include about 14% of the US population.

The weight of evidence from research on this allele suggests that this risk factor interacts with lifestyle factors. Carriers of this allele obtain a greater benefit from exercise than non-carriers for late-life cognitive functioning. This benefit is most strongly evidenced when the exercise is carried out in mid-life. Cognitive experience also confers stronger benefits on allele carriers than people who do not carrier the allele. Understand that cognitive experience benefits everyone, but it is even more beneficial for those carrying this threatening allele.

So no evidence has been found that condemns any of us to Alzheimer’s or dementia. The activities covered in Nurturing the Older Brain and Mind and the healthymemory blog should be undertaken by all of us. This advice is further underscored for those with risk factors.

© Douglas Griffith and, 2014. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and with appropriate and specific direction to the original content.


August 18, 2010

This blog post is another in the series inspired by the book, The Scientific American Brave New Brain.1 That book presents a table contrasting the way the brain once was regarded, the way it is presently regarded, and some conjectures about what tomorrow might hold. According to Brave New Brain, we once thought that environment determines mental potential and that today we think that genes determine mental potential. Here I must take strong exception to Brave New Brain. There were some philosophical arguments that the mind began as a blank plate, tabula rasa, and that experience was written on that plate. The father of behaviorism, John Watson, argued that he could take an infant and raise it to be anything, a butcher, a baker, a candlestick maker, a physician, a lawyer, another psychologist. For him the environment determined everything and that if the proper environments were provided a child could become anything.

Even before Mendel discovered genes, there was the notion of blood and royalty. Certain people were regarded as inherently superior to others. When genes were discovered, some thought that there might be a scientific basis for this superiority, and that genetics could account for individual differences. According to Brave New Brain, that is the current belief. This is certainly not the case. Early in the twentieth century intelligence tests were developed. Arguments as to know much intelligence is attributable to genetics and how much intelligence is attributable to the environment raged. Charges of racism entered these arguments and charges and evidence that IQ tests were culturally biased raged. It should be noted that there are statistical techniques and research designs (controlled identical twins studies, for example) that allow estimates of what percentage of intelligence is genetically determined and what percentage is due to the environment. But these are statistical abstractions. Nature (genetics) and nurture (environment) are inextricably intertwined; they never appear in isolation.

The recent birth of the study of epigenetics has highlighted the interaction between the environment and genetics. The genome cannot be considered alone. Another layer of information stored with the genome is called the epigenome. It is a chemical switch that determines which genes are activated and which genes remain dormant. It does not alter the genetic code, but affects the specific expression of genes. It shuts down or revs up the production of proteins that affect mental states.

Today we know the role of epigenetics. The question for the future is how well can we develop our understanding of epigenetics and whether we can use it to enhance brain function. Research using mice provides reasons for optimism. One study involved mice that were born with genetic disorder resembling mental retardation. They were given a drug that activated epigenetic activity three hours before a training session. They exhibited no learning problems. So perhaps someday mental retardation might be remedied via epigenitic manipulation.

Drugs are not necessarily required for epigenitic manipulation. Researchers at MIT restored mouse memories by enriching the rodents environment. Not only were memories restored but evidence of epigenetic activity was found. Research on the benefits of enriching environments was done years ago, but that was before anyone had ever heard of an epigenome.

1Horstman, J. (2010). San Francisco” Jossey-Bass.