It has long been thought that genes are fixed from birth and that the expression of genes is not affected by the environment. There is, however, evidence that the expression of our genes is less “fixed” than we thought, and that our environment and our experiences can alter how our genes work.
Since the study of epigenetics emerged in the 1940s, scientists have learned that certain environments promote the switching on or off of certain genes at certain times. These biological processes, which we call epigenetic modifications, can define how the information in genes is expressed and taken up by cells.
This research can help explain how cells carrying identical DNA differentiate into different cell types, and how they maintain these different cellular states. In this way, epigenetics is considered to act as a bridge between our genetic make-up and our environments, which both shape our personality and behaviour.
What Is Dopamine?
Dopamine is one of many neurotransmitters in the human brain. A neurotransmitter is a chemical released by nerve cells to send signals to other nerve cells, and this allows neurons to communicate information.
The brain has several distinct dopamine systems, one of which plays a major role in feelings of pleasure as well as reward-motivated behaviour. Most naturally rewarding stimuli that are required for our survival as a species, such as food and sexual activity, increase the level of dopamine in the brain.
Dopamine helps to organise our behaviour so that we are more likely to get things we need to survive. For example, dopamine activity increases when we are successful at getting something we desire. This is linked to feeling good, and increases the chance we will do the same thing again.
However, dopamine activity dramatically decreases when we are unsuccessful at getting something we want. This is associated with feelings of frustration, prompting us to try a different strategy next time. In this way, dopamine helps us learn how to get what we want from our environment.
A variety of drugs of abuse also increase dopamine neuronal activity and appear to “hijack” this motivation system, which is why they are thought to be so addictive.
What Is Brain Plasticity?
Humans are born with largely underdeveloped brains. In fact, the human brain takes the longest of all mammals to reach maturity – around 25 years from birth. During this time the brain undergoes a number of structural and functional changes. Structural changes refer to how the shape, volume and connections between neurons change, while functional change refers to how the pattern of electrical activity in the brain changes.
These developmental changes are examples of the plasticity of our brain, and largely explain why our mental and physical abilities change so dramatically throughout our childhood and into adulthood.
Even when the brain has reached maturity there are some areas of the brain that remain plastic and can be remodelled through experiences in adulthood. However, the degree of brain plasticity in adulthood is considerably reduced compared with childhood.
