1.1 Brain architecture
Brain development begins soon after conception and continues well beyond birth. The building blocks of the brain – specialized cells known as neurons – and the basic structures are formed before birth. Genes, the basic physical unit of heredity, are also key to brain development. Genes and experiences work together, and we can think of them as being inextricably linked. Genes set the parameters for 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.
For some background on gene expression, listen to these explanations by child psychiatrist Sir Michael Rutter of King’s College London and neuroscientist Dr. Charles Nelson of Harvard University.
The next interactive activity provides some clear visuals to help you understand how, physiologically, genes ‘listen’ to the environment.
Listen now as Sokolowski describes cell differentiation during the early prenatal period. She discusses differential gene expression that leads to the production of different types of cells. – Not available in this preview.
The following reading describes brain development during the prenatal period and following the baby’s birth.
The next game will help you review key points from the reading: – Not available in this preview.
The link below is to part of an interactive website about the human brain and behaviour called The Brain from Top to Bottom. Visit the section below for a wealth of information on brain changes from conception through the embryo stage.
Neurons
Neurons are the basic building blocks of the brain. Each neuron has a nucleus, axons and dendrites. The connections between neurons are called synapses. Neurotransmitters are chemicals in the ends of the axons that carry messages across the synapse from one neuron to the next. Connected neurons make up millions of neural pathways in our brain and in the central nervous system.These pathways form the brain’s communication system with the rest of the body. Glial cells are another type of neural cell that help to support and protect the neurons forming neural pathways.
Based on interactions between genes and experience, neurons are connected to form networks. Even during pregnancy, experiences and genes interact to establish neural circuits and shape the brain’s architecture. We know from research that many experiences during pregnancy have the potential for detrimental life-long consequences on fetal brain development, for example: exposure to tobacco, drugs and alcohol; violence during pregnancy; certain medications; limited access to prenatal care and screening; and environmental hazards.
Building neural connections and pathways is not all that happens in the first months and years of life. Neurons, connections and even whole neural pathways are discarded, while others are strengthened. The brain increases its efficiency by eliminating little used pathways and reinforcing useful ones. This process of connecting (“wiring”) and refining (“sculpting”) continues through infancy, childhood and adolescence. Synaptic connections are overproduced then pruned over time, so that by age six, a child’s brain has many more synapses than the adolescent or adult brain.
In the next video, Sir Michael Rutter discusses that biology is not deterministic. While genetic programming organizes neuron development, there is individual variation in that neural connections that aren’t being used are pruned or eliminated. – Not available in this preview
Brain structures
This PBS website contains a 3-D tour of the brain. Explore the areas of the brain as well as the functions of each area. Note: You may get a message prompting you to download the “Shockwave Player” to view this site. Just follow the instructions on the site.
The following activity shows a way to demonstrate the structures of the brain, using your hands.
The brain is divided into three regions from the most primitive to the most evolved brain area: 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 four lobes: frontal, temporal, parietal and occipital. Play the following game to learn more about the brain structures.
The following labelled diagram provides more information on some brain structures, including the four lobes within the cerebral cortex. Play the game that follows to test your understanding of the function of each brain structure. – Not available in this preview
