The most effective methods of pedagogy (the theory and practices related to teaching the young learner) and andragogy (specialized strategies for adult learning) should not be practiced without an understanding of the human brain. Educators should be intimately familiar with important principles of cognitive science. If they are not, they will try to force 4.2 million years of brain development into the practices and assumptions of the 140 year-old model used in contemporary education. This model is not working well and warrants the exchange of older components with more brain-considerate practices.
Macroscopic View of the Human Brain
The human nervous system is composed of two major parts: the peripheral nervous system and the central nervous system. The sensory receptors of the peripheral nervous system (PNS) receive stimulation from the outside environment and forward it to the central nervous system (CNS) where the incoming information is systematically processed. The CNS is made up of the spinal column and the brain, forming the central command station. Typically, the spinal column sends information to the brain for sophisticated processing, decision-making, and other deliberate actions.
The human brain is divided into three interconnected anatomical components or regions: the cerebrum, the cerebellum and the brain stem.
The cerebrum makes up the largest part of the brain and has changed very little over the past 130,000 years. It is divided into distinctive asymmetrical left and right hemispheres which oversee specialized brain functions. The most striking feature of the cerebral cortex, home to all higher human brain processes, is the wrinkled two-millimeter-thick surface of the cortex. These folds permit the fixed interior volume of the human skull to house a fairly large amount of cortical surface tissue. If the human brain were “unfolded” and stretched out, its surface area would be approximately the size of a desktop (2.5 square feet or 2500 cm2). Six paper-like layers are neatly stacked together as the arranging principle underlying the cerebral cortex. The interactions of these neuron-rich layers foster the biological basis of all human behavior.
Normal human brains are lopsided, the left hemisphere being generally larger and more active than the right. Paula Tallal, of Rutgers University, and others have noted that whenever the two sides more closely approximate symmetry, the left hemisphere is usually somewhat underpowered. This symmetry is suspected as a leading cause in incidences of male language deficits and disorders. In females, the left hemisphere is typically larger than the right. However, the male brain appears slightly more symmetrical, as the average male brain comes equipped with a larger right hemisphere than would be typically found in females.
The second brain component is the cerebellum, a cauliflower-like structure that sits immediately behind and below the cerebrum. The cerebellum facilitates tasks such as balance, movement and coordinating the body’s senses. It orchestrates many of our automatic behaviors. Every time we get up in the morning, stand at a podium, or walk down the corridor, our cerebellum deserves an immense amount of the credit. The third brain component, the brain stem, controls the body’s vital processes such as heart rate, breathing, etc.
Three Critically Important Brain Processes
Synaptic Proliferation
Neurons constitute the basic building blocks of the mammalian brain and the spinal column, transmitting commands and information to muscles and glands and other neurons. Neurons are separated by synapses, the microscopic contiguous gaps between brain cells. These junctions form tiny synaptic gaps that are approximately 0.02 microns (8 millionths of an inch) wide. Synapses link the cells inside the brain through the process of synaptogenesis, which organizes those cells into the all-important operating circuits. Following birth, most new synapses come by way of new experiences or through pre- programmed genetic instructions. Billions of synapses form in utero, while trillions more will develop as a result of postnatal stimulation and learning experiences. Physically, synaptic connections build the neural networks that make the vast catalogue of human behaviors and all learning possible.
During neurogenesis, there is an overproduction of synapses, synaptic proliferation, which does more than just ensure that enough connections are available for the awakening body to “turn on” and operate the heartbeat, muscles, lungs, eyes, and other organs. This excess of connectivity provides its owner with a neural insurance policy for the young brain. Synaptic proliferation guarantees that the young brain is capable of adapting to virtually any environment into which a child is born. Thanks to this overabundance of synapses, the growing brain eventually has the neurological wherewithal to blend itself comfortably and seamlessly within a specific external environment.
A toddler’s brain has twice as many synapses among its 100 billion neurons as does the brain of a fully matured adult. His or her brain also operates at an energy level that is 225% of the capacity of an adult’s brain. This is a result of “wiring up” the neurons in his developing brain as he responds to the local environment. A single neuron may have as many as 50,000 dendrites, which are the short threadlike fibers that extend themselves away from the neuron’s cell body in order to receive electrochemical signals from other active neurons. With new learning, dendrites respond by reaching out to one another in an elaborate branching process that bonds previously unaligned brain cells with one another, thereby creating complex neural circuits. The outcome of these extensions or “dendritic trees,” is “dendritic density,” the formation of dense neural “forests” that are the neurophysiological by-products of learning within a stimulating environment. Synapses reach the peak of their postnatal production levels during approximately the fifth year of life, during kindergarten.
Neurons communicate when the chemical composition of a pre-synaptic or sending neuron’s cell body is modified by the in-coming chemical signals transmitted from another neuron. An electrical impulse or signal is sent down a neuron’s axis at speeds up to 270 miles per hour. The electrical impulse causes the tiny chemical reservoirs (synaptic vesicles) at the end of the neuron to rupture, sending neurotransmitters, the chemical messengers, across the synaptic gap to the post-synaptic or receiving neuron. The molecules released by one neuron traverse the synaptic gap and bind at the receptor sites of the next neuron, causing a chain reaction along a neural pathway. Neurons send messages to and from one another permitting vital information to travel from one part of the brain/body to another. These chemical communications sponsor all human thinking, learning, and behavior.
Neurotransmitters can be excitatory or inhibitory, sending signals for cells to communicate, or explicitly instructing them not to communicate at all. When the lightning-fast electrical impulse flashes and prompts the discharge of its chemicals, the process mimics the sequence of events taking place during a winter storm, giving rise to a unique neurophysiological interpretation of the term brainstorm.
Neural Pruning
All efficient organisms need a method by which unused or damaged cells are discarded. Even healthy brain cells will perish through neural pruning if they fail to find a job to perform during the critical or sensitive periods of development. There is no neuronal welfare agency operating inside the cranium that is designed to sustain non-working neurons. Controlled cell death, or apoptosis, is a merciless process that occurs by necrosis, deliberately killing brain cells. Each neuron must connect to a functioning neural pathway or it will be subjected to programmed neural cell death.
As the twentieth week of fetal life approaches, nearly 200 billion neurons have already been created. During the third trimester, the process of neural pruning occurs to reduce the dangerously excessive numbers of brain cells. Following this pruning period, only fifty percent of the original cells remain. The surviving 100 billion neurons are ready for assignment to a functional neural circuit at birth. The appropriate number of postnatal neurons is critical in forming highly functional networks that will aid the growth and development of a thriving newborn.
Following birth, billions of synapses are nourished while others are eliminated over time, changing the nature of how information gets communicated among the neurons. Future cortical adaptations will come by way of further synaptic pruning to reduce the numbers of synapses. Some neural pruning results from healthy environmental stimulation, while the balance typically occurs from the lack of stimulation, poor nutrition, reduced physical activity, minimal social interaction, or abuse. Under these adverse conditions, there will often be a decrease in neurons, a correlative decrease in the thickness of the cerebral cortex, lower numbers of synapses, and accelerated synaptic pruning in cases of extreme impoverishment.
Apoptosis, the regulated destruction of a cell, may be triggered by either external or internal factors. If a child does not hear words by the age of nine or ten, he or she will encounter enormous difficulty in ever learning to speak any language and may not speak at all. The lack of any visual stimuli reaching the visual cortex for processing during infancy can rob a healthy eye of the gift of sight. Only those brain cells with important linkages to active neural circuits are permitted to survive the ongoing pruning-down and linking-up processes to which most neural networks are subjected.
Cortical Plasticity
Brain growth and development are immensely influenced by cortical plasticity, the brain’s remarkable ability to allow different regions, structures, and connections to change physically as a consequence of experiences and input from the external environment (e.g., Goldblum, 2001; LeDoux, 2002). Connections among the one trillion brain cells are consistently impacted by incidents processed consciously and unconsciously. Synapses are also changed by experience as the neurotransmitters released by a particular synapse are modifiable. Neurons release multiple neurotransmitters and/or neuromodulators and are capable of altering their chemical messages over time.
As new behaviors, skills, and learning tendencies emerge, there are neurophysiological correlates representing each of them. They largely determine how much cortical growth will take place, in what regions the growth will take place, and where subsequent development will occur or become delayed. The very architecture of each human brain is adjusted as a result of all newly acquired competencies. Even the corpus callosum, the neural superhighway connecting the two corrugated hemispheres of the brain, is modified by skills development. There is recent evidence that literacy can impact the thickness of this connecting structure. These processes pave the way for a uniquely structured brain within every individual.
Neurophysiological processing does not change from the early pre-school learner to adults, although the brain continues to reorganize itself. Neural patterns with the greatest likelihood of developing elaborate neural connections are those emerging talents and capabilities that an individual devotes significant amounts of time and attention to, those that have key emotional, personal or survival value, and those that are often repeated. These neural patterns are nearly impervious to destruction short of disease or regional brain trauma (Black, 2002). Substantial amounts of nerve growth factors, vital for brain cell growth and survival, are regularly carried to these essential regions and circuits, assuring their continued healthy existence.
A high level of dense neural connections represents one’s acquired knowledge, abilities, and skills. Thus, it is easier to expand concept understanding by tapping into the existing fertile networks that correspond to a person’s strengths. A comparatively large number of neural pathways must exist to support proficiency or mastery. These efficient circuits are subsequently used in skill enhancement or refinement and play a vital role in the comprehension of newer, but related, concepts or events. We use stored knowledge bases to dissect, process, and make sense of novel experiences in order to understand and act upon them. The absence of an adequate neuronal investment is often responsible for talent deficits, conceptual misunderstandings, and learning difficulties.
Unfortunately, schools spend an inordinate amount of time identifying academic deficiencies and devote even greater numbers of hours to subsequent remediation by concentrating on a student’s problem areas. Instead, schools should focus on further cultivation of a student’s strengths which indicate the presence of healthy, efficiently working neural networks (e.g., Clifton & Anderson, 2002; Kovalik & Olsen, 2001). This focus will result in far more cognitive resources to work with in any plan for performance improvements or skill level enhancements in the classroom. A disproportionate level of cortical real estate gets devoted to proficient skills, and an abundance of complex learning networks are dedicated to supporting those manifested competencies.
There is an interesting method by which the brain oversees and modifies the distribution of cortical real estate. Certain areas of the body have more neurons and more cortical space designated for them. The undemocratic assignment of cortical territories is initially based on the degree of importance that a given area of the body has in relation to one’s survival. However, the brain is not a static organ. Later, the allocations are gradually but regularly reallocated as a consequence of how frequently a particular area of the brain is used, how its related functions are valued in one’s specific environment, and its importance to survival and emotional fulfillment.
For example, if a region of the motor cortex responsible precisely for right-hand movement in a human is damaged, the use of his right hand will be substantially diminished or lost completely. Conversely, if movement in the right hand is grossly limited, the cortical regions of the brain responsible for movement in that hand will atrophy. Interestingly, the cortical areas representing the opposite (left) hand will often increase to compensate for the loss of right-hand use, and a marked improvement in left-hand dexterity and proficiency will take place. This phenomenon, known as compensatory hypertrophy, is how all brains physically reorganize themselves in such a way that the opposite hand (or leg, or eye, etc.) gets stronger as a response to the lost service of its counterpart. Thus the brain adapts to life’s changing conditions, always looking toward survival and the future.
Many “facts” in the field of neuroscience continue to change based on new research. It is now a widely accepted fact that neural plasticity takes place in the sensory-motor cortex at all ages, and that the brain continues to rewire itself as it responds to new input, permitting new learning, new skills, and new behaviors throughout a lifetime (Byrnes, 2001). There is also evidence that the human brain actually does grow new neurons in the cerebral cortex throughout our lives. This discovery has forced us to re-write our “brain facts,” and it is revolutionizing our understanding of postnatal neural regeneration (Nathanielsz, 2001).
Concluding Thoughts
Through its elastic power to undergo physical and chemical changes as it responds to its environment, the human brain may either expand or shrink based on the quality, quantity, and richness of the learning experiences encountered. Neural plasticity is one of the chief cognitive enablers of all formal education benefits. The latest findings in neuroscience leave little doubt that the human brain grows and feeds on consistently healthy stimulation. Unfortunately, the very same healthy cerebral cortex can also exercise its flexible nature and be molded by severely negative events. But when the brain is properly nourished and allowed to grow and develop in a positive, reassuring, and encouraging atmosphere, it responds favorably to that rich supportive environment. Under these conditions the probability of maximizing the brain’s remarkable potential increases dramatically. When the opposite conditions prevail, whether early in life, later in life, or consistently during one’s life, there is a frightful price to pay. The neurophysiological costs are seldom cheap and rarely short term.
With the latest discoveries, the human brain is regaining its rightful place as the centerpiece for all conversations about learning. Understanding how the brain processes information can assist kindergarten through university-level educators in crafting instructional practices and designing classroom environments that are consistent with the brain’s natural inclinations for learning. Devising methodologies that accommodate the brain’s processing techniques will enhance the prospects of academic success for any student, regardless of age.
References
Black, I. B. (2002). The changing brain: Alzheimer’s disease and advances in neuroscience. UK: Oxford University Press.
Byrnes, J. (2001). Minds, brains, and learning: Understanding the psychological and educational relevance of neuroscientific research. New York: Guilford Press.
Clifton, D. O., & Anderson, E. (2002). StrengthsQuest: Discover and develop your strengths in academics, career, and beyond. Princeton, NJ: The Gallup Organization.
Goldblum, N. (2001). The brain-shaped mind: What the brain can tell us about the mind. UK: Cambridge University Press.
Kovalic, S. J., & Olsen, K. D. (2001). Exceeding expectations: A user’s guide to implementing brain research in the classroom. Covington, WA: Susan Kovalik.
LeDoux, J. (2002). Synaptic self: How our brains become who we are. New York: Viking Press.
Nathanielz, P. (2001). The prenatal prescription. New York: HarperCollins.