1.1 Brain architecture
As described on the previous page, the basic structure of the brain is being formed before a child is born and grows rapidly in the first three years of life as illustrated in the Brain Growth graphic.
The building blocks of the brain are specialized cells known as neurons. Neurons and basic brain structures are formed before birth. These are described further down on this page. First, learn more about genes, which guide the set up of the brain.
Inside the neurons or brain cells is where our genetic material – genes and DNA – are located. Genes are the basic physical unit of heredity, and together with the influence of the environment, set up the basic structures of the developing brain.
In the next video, biologist Dr. Marla Sokolowski of the University of Toronto describes what a gene is.
As we saw on the previous page, experiences after birth also play a big role in how the brain (and the person) develops. Genes and experiences work together. Genes guide the basic structure of the developing brain. Experiences affect how genes are “expressed”. Dr. Charles Nelson of Harvard University explains gene expression.
Nelson explains that gene expression is influenced by the environment; in other words, one’s experiences. In the next video, Dr. Meaghan Jones, of the University of Manitoba, uses the analogy of a dimmer switch to explain epigenetics.
In the next KidCareCanada video, Dr. Thomas Boyce adds to our understanding of epigenetics and explains that experiences – both positive and negative – affect how genes are expressed without changes to the genes themselves.
Neurons and synapses
Neurons – brain cells – are the basic building blocks of the brain. The connections between neurons are called synapses. Neurotransmitters are chemicals that transfer across the synapse from one neuron to the next.
Connected neurons make up millions of pathways in our brain and in the central nervous system (includes the brain and the spinal cord; receives input from all body parts and coordinates activities). The “wiring” of these pathways is how the brain “communicates” with the rest of the body.
More neural connections are developed in the first few years of life than at any other time. In fact, over 1 million neural connections form every second during these years (Center on the Developing Child at Harvard University, Brain Architecture, n.d. para 2). These connections are important in building a healthy brain.
Connections form because of interactions between genes and experience. Even during pregnancy, experiences and genes interact to establish pathways and shape the brain’s architecture. We know from research that many experiences during pregnancy can have serious, life-long consequences on fetal brain development. Some examples are:
- exposure to tobacco, drugs and alcohol, certain medications
- violence during pregnancy
- limited access to prenatal care and screening
- environmental hazards
Building neural connections and pathways is not all that happens in the first months and years of life. Some neurons, connections and whole pathways are eliminated, while others are strengthened. The brain becomes more efficient by getting rid of pathways that are not being used and reinforcing the more useful ones.
This connecting (“wiring”) and refining (“sculpting”) continues through infancy, childhood and adolescence. Connections are overproduced and then pruned over time, such that by age six a child’s brain has many more synapses than the adolescent or adult brain.
Brain structures
The brain is divided into three regions: the hindbrain, the midbrain, and the forebrain. These three regions include the main structures of the brain. The hindbrain at the back of the brain includes the cerebellum. The brain stem is in the midbrain, at the base of the brain. The forebrain includes the corpus callosum, limbic system, and cerebral cortex.
In humans the cerebral cortex is highly specialized and significantly larger than the cortex found in other mammals, including monkeys and chimpanzees. The cerebral cortex is comprised of two hemispheres (right and left), each of which is divided into five lobes: frontal, temporal, parietal, occipital, and insular. Play the following game to see where the brain structures are located. (Note: the insular lobe is not included.)
The following activity shows a way to demonstrate the structures of the brain, using your hands.
The following labelled diagram provides more information on some brain structures. After reviewing the diagram, play the game that follows to test your understanding of the function of these brain structures.
On the next page, you will look more closely at how experiences early in life affect the developing brain. Remember, genes determine the basic structure of the brain, but the quality of experiences has a big role to play.
