Brain Development

Summary:

Prenatal Period

The formation of neurons begins in the prenatal period. A few weeks after conception, the neurons begin dividing and migrating to their specific area of the brain. In this stage, the neurons will also begin myelination which is the forming of the myelin sheath around the axon of the neurons.

Newborn Period

At birth, the newborn brain has about 100 billion neurons and weights 2/3 to 3/4 pounds. The areas in charge of basic survival and reflexes are almost fully developed and the neurons controlling vision and hearing are quickly developing at this stage. The connections of neurons in the brain begin to rapidly develop in the newborn period.

Childhood

During early childhood the brain goes through rapid change. The brain forms and refines neuron networks through the processes of synaptogenesis, pruning, and myelination.

Synaptogenesis is the process of forming connections in the brain. This process, although it is biologically driven, is affected by experiences. During early childhood the brain will go through a process called synaptic overproduction which is when the brain forms more synapses than it will use. That’s when pruning comes into the picture. Pruning is the process that refines the synapses, which were created during synaptogenesis, based on experience. The connections that are used regularly are strengthened, and the connections that are not are pruned by the brain.

Adolescence

The brain of an adolescent reaches its adult weight at about fourteen.  Myelination in the frontal lobes enables the adolescent to become more capable of insight, judgment, inhibition, reasoning, and social conscience.  This front lobe development continues until age 25-30. The regions responsible for judgment, planning, assessing risks, and decision-making are the last areas to finish developing.

In this stage, the connections that are used regularly become stronger and more complex. Pruning also continues through adolescence. Also, new synapses form in response to new experiences.

Adulthood

In adulthood the brain is still changing but at a much slower rate than in childhood. The brain continues to develop connections but they are formed based only on specific experiences.

Keeping the mind active is important in order to prevent brain atrophy. Activities such as reading, crossword puzzles, talking to others, and maintaining relationships can help maintain healthy brain growth.

Analysis:

The fact that neurons form in the prenatal period and that the areas in charge of basic survival and reflexes are highly developed at birth shows that everyone starts with pretty much the same abilities. Synaptogenesis is also a biologically driven process. All of this is then shaped by experience. If an infant is not exposed to new information and experiences during early childhood, many of their synaptic connections will be lost. Early childhood is a critical period during a person’s life that can definitely affect that person’s intelligence levels later on. If the connections are used regularly and the brain is kept active these connections will become stronger and more complex which will lead to higher intelligence levels. Exposure to new experiences is important, not only during childhood, but all throughout that person’s life in order to keep the brain active.

Questions:

·         What could be the consequences of lack of exposure to experiences during early childhood?

·         What plays a bigger role, genes or exposure to experiences?

Link:

http://www.fcs.uga.edu/ext/bbb/brainTimeNewBorn.php

·         Brain development timeline. (2012). Retrieved from http://www.fcs.uga.edu/ext/bbb/brainTimeNewBorn.php

Epigenetics


Summary:

          Epigenetics is the study of all modifications to genes other than actual changes in the DNA sequence itself. Although we can’t change genes that are already in our DNA, it is possible to control the switching on and off of these genes. This is what epigenetics strives to understand and achieve. Being able to accomplish these genetic alterations comes with great advantages such as the treatment of inherited diseases and cancer.

          What we know as “good genes” or “bad genes” is not as important as the actual activation of these genes. Genes are in charge of providing cells with instructions to make proteins. In the cell, DNA sequences are transcribed into RNA, which is then translated into the sequence of a protein. Epigenetic modifications, by turning genes on or off, allow or prevent the gene information from being transcribed into a protein.

          For example, in cancer, tumor-suppressor genes are mistakenly turned off, which prevents the growth-limiting protein from being made. Also, there are many growth-promoting genes for which a single dose is enough for normal cell proliferation. But if another copy of this growth-promoting gene is mistakenly turned on, uncontrolled cell growth can occur.

          Epigenetic changes can be caused by environmental factors such as diet, exercise and drugs. But what’s even more surprising is that these alterations can also be caused by exposure to other people in whom the genes are already active. This supports the idea that “You become more like whatever you are surrounded by.” It also explains familial traits, which are the characteristics shared within a family but that are not genetically inherited.

          Epigenetics alterations are not concrete. Instead, they are present throughout the lifetime of a person and are generally accumulated over time. For example, identical twins, although they have the same DNA, may have different epigenetic material due to difference in their environments.

          Epigenetics also explains brain plasticity, not only in the neurons themselves, but also in the genes that enable or disable their function. Certain environmental cues are necessary for turning on certain genes in charge of network development. However, if these cues aren’t present, these genes may not be activated. Also, wrong environmental cues can cause dysfunction. Environment plays a huge role in manipulating the structure and function of neurons. This proves that intelligence enhancement is possible and epigenetics shows how this alteration works. Epigenetics will also all
ow us to determine the factors that affect intelligence growth and decline.

Analysis:

          Epigenetics shows how nature and nurture interact. Although most of our characteristics are genetically predisposed, our environment determines to what extent we will be affected by them. This applies to the genes responsible for intelligence. We could have them or not, but that wouldn’t be as important as knowing how to activate and use them to their full potential. In a previous source, it was mentioned that every human is born being a genius, but not all of us take advantage of that privilege. If certain environment cues are not present or if we are influenced by the wrong ones, our level of intelligence could be altered. What we eat, how often we exercise, and whether or not we take certain drugs are all factors that could affect our intellectual power. Even the people we spend a lot of time with could influence the development of some genes that may or may not be responsible for intelligence. Although there is still not a specific way to control the activation of these genes, thanks to epigenetics we are closer and closer to finding this answer.

Questions:

• Is it possible that spending time with people with higher intelligence levels affect our own intellectual power?
• If scientists developed a drug that could activate these "intelligence" genes, what could be the advantages and disadvantages?

Source:
Plasticity & epigenetics: The basics. (2009, April 29). Retrieved from http://neurohackers.com/index.php/en/menu-top-nhalib-neurohacking/37-cat-nh-basics/69-plasticity-epigenetics-basics

Link:
http://neurohackers.com/index.php/en/menu-top-nhalib-neurohacking/37-cat-nh-basics/69-plasticity-epigenetics-basics