Monday, October 21, 2013

Our genome as a memory stick

We tend to see humans as a combination of nature and nurture, nature being represented by the genes we inherit from parents and nurture by the impact of environment. But the reality is far more complex and subtle. What if the genes are only a biological data base especially built for saving the relevant changes from the environment we live?


 For people who are more or less familiar with psychology there is a well-known theory that intelligence is classified into two main categories: fluid and crystallized. Fluid intelligence is thought to deal with solving new problems, while crystallized intelligence is a sort of reservoir of knowledge. And the later are thought to be developed through the investment of fluid intelligence (hence the name “investment theory of intelligence”). But a new  study made by Dutch scientists from Tilburg and Amsterdam universities contested this view. In striking contrast with the general view that fluid intelligence would have a heavy genetic base while the crystallized one would be based on learnt knowledge or cultural load rather than genes, this new study found the exact opposite. Using an IQ test which has both culture free and culture loaded items, they found that highly culturally items had higher heritability coefficients (hence a stronger genetic component) and were also highly related to general IQ score. How to interpret these findings? The authors advanced the theory that people with more complex minds tend to seek out intellectually demanding environments, and as they develop higher levels of cognitive ability, they will be more favored to achieve higher levels of knowledge. So cognitive abilities and knowledge dynamically feed off each other. This is similar with studies which tried to find if there is an effect of brain fitness exercises on increasing the performance of working memory and attention. They found that these exercises help especially people with more powerful minds, not those with poorer cognitive abilities – which should be the main beneficiaries of this sort of training. Why? Because smart people tend to be more interested in self development, seek out more stimulation and also are more able to motivate themselves long enough (6 weeks of daily exercising) to benefit from the effect of this enduring mental training. 
It seems that societal demands influence the development and interaction of multiple cognitive abilities and knowledge, and giving rise to general intelligence factor. This is something similar to the Flynn effect. The Flynn effect is the substantial and long-sustained increase in fluid and crystallized intelligence test scores (average test scores) measured in many parts of the world from roughly 1930 to the present day. Some explanations have included improved nutrition, better education, and greater environmental complexity. The fact is that this effect tends to be strongly associated with the economic boom of a country.



As I mentioned above, brain fitness exercises increase performance of working memory and attention. In addition, another type of mental exercise – mindfulness meditation is proved to strengthen connections between regions of the brain called Default network and to increase the volume of the hippocampus (a brain structure critical for learning).  The brain’s Default network comprises several brain regions which are viewed as the biological basis of Self, storing our life experiences and contributing to introspection and other self-relevant processing, but also to creativity. Also these people which meditate 20 minutes a day for 90 days develop a more wrinkled cortex – the brain outer layer which is used for the most sophisticated mental abilities – and their brain become more efficient. Animal studies using enriched environment also discovered the effect of environment upon the brain. Enriched environment means housing mice in complex cages, where they have the possibility to play with toys, to explore, to make physical exercises and to interact with other mice. All these impact the brain’s circuits responsible with learning, increased brain plasticity and modify the expression of more than 40 genes involved in learning, building synapses and regulating blood supply in the brain.
So we have an important clue here! The environment, a new, complex environment seems to modify brain’s circuitry involved in learning and also the expression of the genes which build the brain. This process is called epigenetics, and represents the ability of the genes to be changed in their expression by the environment. And also to pass these changes to the next generation. So the environment leaves a mark on the brain, even a genetic mark, and this mark is heritable. This is the explanation for the discovery of the Dutch scientists presented at the beginning of this post. In psychology there is the assumption that genotype (meaning genes) and environment are independent and do not covary. These data suggest they very much do.

The tools we use during our lifetime, the games we play, the gadgets, the internet, all of these seems to shape our genes. Genes are not something created to build “the brain”. They are building specific brains according to the environment were that species use to live.  In the last 5000 years approx. 7 % of our genes have changed. And given that life on Earth is 3,5 billion years old, and our species is 190.000 years old, 5000 years is a blink of an eye! The human brain has adapted to the cultural information from the environment and these adaptations changed the expression of its genes. And some of these changes are passed to the next generation in order to be more adapted. Part of our culture is already in our genes and probably we can say that basically they are a biological form of culture.


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