“The brain is without doubt our most fascinating organ. Parents, educators, and society as a whole have a tremendous power to shape the wrinkly universe inside each child’s head, and, with it, the kind of person he or she will turn out to be. We owe it to our children to help them grow the best brains possible.” – Lise Eliot
Parents and educators are among the most voracious consumers of the latest research about the brain, searching for strategies to enhance learning and brain development. They are finding a wealth of new answers. Discoveries from the field of neuroscience are reported in the media almost daily. Twenty Nobel prizes have been awarded to neuroscientists during the past 26 years, as they open windows into the workings of the human brain.
Though we often say that we learn “in school,” learning actually takes place in the brain. It happens anywhere, anytime we encode an experience as a memory. Our cerebral universe never stops moving and changing as long as we are alive. Learning impacts how the brain is built in its developmental stages, and the ways in which it changes over a lifetime. UCLA neuroscientist Dr. Robert Jacobs found that college graduates create up to 40% more brain connections than those with only high school diplomas or less. Other researchers have concluded that those additional connections can protect our brains from Alzheimer’s disease by making it easier for an impaired brain to re-wire itself.
What is Neuroplasticity?
Although we cannot regenerate limbs, we can re-invent our brains (and thereby ourselves) through neuroplasticity. Early theories depicted the human brain as a “machine,” which could not physically change its makeup. Today, we know that our brains undergo daily renovations to adapt to our ever-changing world.
By the 20th century, genetics was widely accepted as the basis of human characteristics, displacing John Locke’s 17th-century notion of the tabula rasa, which suggested that the mind started as a blank slate from which our competencies, including intelligence and personality, were developed. Locke and others argued that the environment indelibly etched its signature on each individual. The resulting “nature vs. nurture” binary dispute is collapsing today under the weight of a mounting body of evidence. Yes, we enter the world with some brain physiology already set, but each brain is reshaped into its own unique configuration.
Open architecture is a computer science term used to describe processing systems that can adapt to changes in user requirements. Similarly, in neuroscience, brain plasticity refers to the ability of the brain to modify its structures and neural mechanisms. Changes in brain function occur as the brain re-wires itself in response to new demands placed on it by the external environment. Our malleable brains help us thrive by crafting environmentally appropriate survival strategies. Brain plasticity underlies the brain’s extraordinary capacity to learn, unlearn and relearn.
How is the Brain Organized?
A significant part of neural processing is the coding of sensory stimulation. Information enters the brain in the form of sensation, auditory and visual information. All incoming stimuli, with the exception of data sent through the olfactory system, are first channeled through the thalamus – the “waiting room,” where sensory information is sent before going to the cerebral cortex where it is disaggregated into its constituent parts. Each element – colour, motion, lines, angles or texture – is sent to a specialized region of the cerebral cortex for processing. The brain compares the new information to aspects of earlier experiences that are already stored in permanent memory. If a match is found, an appropriate response is performed. Our response time to familiar stimuli grows faster as those reactions become hard-wired.
Examining the brain at the macro level, the cerebral cortex is composed of four large lobes, each of which can be subdivided into as many as 200 functional areas. Damage to a particular cortical area can disrupt or destroy any given competency. With today’s brain-mapping techniques, we can predict precisely which capacities will be diminished or lost through damage due to disease, stroke, injury or disuse.
Without your brain’s high degree of variability, what would make you any different from the next person? There is a unique cytoarchitecture, representing the special cellular organization and the precise connections inside each human brain. Neural pathways connect the brain stem, cerebellum, and subcortical structures (including the limbic system) to specific areas of the cortex, which are rearranged by the minute to reflect our most recent experiences. Since nature only allows us one chance to make a fatal blunder, our neural circuits constantly update our version of the world, which we find full of opportunities to pursue and dangers to avoid. Developing efficient pathways is vital to our survival.
From a micro perspective, the brain is made up of neurons and glial cells. There are over 150 different kinds of neurons, making them the most diverse cell type in the entire human body. The work of each neuron is to carry out the input-processing-output framework of our experiences. Twenty percent of our neurons are inhibitory in function. Their job is to suppress network activation to stop a particular response or behavior. (ADHD arises from an inability to stop a response to one stimulus and choose to respond in a more appropriate manner instead. While this is often referred to as an attention deficit, it is more accurately an executive function deficit.)
Glial cells serve as “nannies” to the neurons. They transport nutrients and oxygen to them and remove debris from them, keeping neurons healthy and alive. Each human brain has over 100 billion neurons: the brain’s “gray matter,” which is composed of neuron cell bodies. Glial cells, however, far outnumber neurons; there are 10 to 50 times more “nannies” than neurons in the human brain.
Neuroscientists are fond of saying, “Neurons that fire together, wire together” and “Neurons not in sync, do not link.” Dendrites form tree-like extensions that put a neuron in touch with as many as 200,000 of its neighbors, resulting in what we call new thinking and learning. When the brain learns, new dendrites grow. Early brain theorists believed that with each new memory, a new neuron grew. Today, we know that newly learned information is encoded as new dendrites sprout to connect neurons to specific sites, producing a new pathway that represents the experience.
In order for us to move, feel and think, neurons relay messages to one another, using both electricity and chemistry. Once incoming stimuli reach a threshold point, a 270 mph electrical impulse “fires” down the axon. Once the electrical impulse reaches the end of the axon, a tiny pocket of chemicals bursts, sending neurotransmitters (the “chemical couriers”) across the synapse, the microscopic space between neurons. As neurotransmitters cross the synaptic gap they lock into receptor sites on the postsynaptic neuron and convey their chemical message only if their molecular properties fit the precise configuration of the receptor sites on the postsynaptic neuron. Over one quadrillion (1,000 trillion, or 1015) synaptic connections can be established inside the human brain.
To optimize message transmission, myelin, a fatty substance, coats the long axonal region of a neuron, speeding up signaling and insulating the axon from extraneous electrical or chemical impulses. A breakdown in myelin exposes the axon to misdirected electrical impulses. When diverted to unintended neurons, extraneous impulses can have devastating mental and physical consequences. Multiple sclerosis is caused by progressive degeneration of myelin.
Different regions of the brain become heavily myelinated during pre-programmed sensitive periods, which opens up windows of opportunity for developing specific skills or competencies. After a region is myelinated, a performance permanence sets in. Language-learning is one example. Every brain begins life with the capacity to learn any of the 6,000 languages spoken on Earth. When a child consistently hears the regular sounds (phonemes) in a given language, neural connections are created in the auditory cortex. The “window” for language-learning closes with the onset of puberty. Afterward, learning a new language will be more difficult and will typically be accompanied by a noticable accent.
Pruning the Garden of the Brain
Synaptic proliferation is the prenatal overproduction of synapses that gives a young brain its incredible adaptability. We are born with many more connections than our adult brains will use. This neural insurance policy guarantees that infants born in San Francisco, Shanghai or Soweto can flourish with equal ease. In the first two decades of life, the human brain “prunes” away connections in a dynamic self-reorganization that operates by the use-it-or-lose-it principle.
There is an old story about a man who walked from his farmhouse to his barn every day. After following the same path day in and day out, it wore into a groove. Eventually, the old man could walk to the barn blindfolded, since the deep channel would steer him directly where he was going. Neural pathways in the brain follow a similar pattern: They are strengthened with repeated use, while neglected networks become unreliable and eventually are pruned away.
Pruning helps the brain protect itself from devoting precious resources to useless networks and inefficient over-wiring. Apoptosis, programmed cell death, eliminates unneeded neurons, just as roads that are seldom traveled fall into disrepair and eventually are closed down for good. Unused skills suffer a similar fate: what we call “forgetting.” (While memory failures are generally due to degraded neural networks, accelerated memory loss is associated with stress, aging or acute brain damage.) Decreased use of skills reduces the nourishment of their networks, diminishing memory and performance.
In the absence of nearby land, some tadpoles will arrest the natural process of metamorphosis into frogs, because environmental conditions suggest that such a change is by no means beneficial to survival. Instead, those tadpoles remain swimmers. It is an apt metaphor for the developing brain.
Mother Nature offers a trade-off: instinct or flexibility. Those species whose behavior is dominated by instinct—e.g. reptiles, fish, amphibians, and insects—have brains that leave little room for neuroplasticity but are highly efficient. As a result, they are less adaptable. Human brains, on the other hand, were shaped by evolutionary pressures that rewarded adaptability. One example of our flexibility is the way our brains accommodate stimuli in multiple patterns and formats, but still accept them as the same object.
Early Brain Growth
Neurogenesis is the rapid production of brain cells in utero, when neurons are produced at the incredible rate of 250,000 to one million per minute. The rapid growth of the young brain system begins 18 days after fertilization. The brain develops quickly through first-hand experiences. Computer simulations and early-learning videos are no substitute for the real world. A mere picture of an orange short-changes the learner, who cannot directly experience its smell, texture, taste and mass. Learners create meaning from what they do in their world, not from exposure to its representations.
While genetics and prenatal influences may calibrate the brain at birth, it is largely dependent on subsequent experiences to determine its capacities and deficiencies. Author Joseph Epstein stated, “We are what we read.” Neuroscientists would assert, “We are what we experience.” Neural circuits are constantly reorganized and rerouted, based on the quantity, quality and timing of our experiences. This has profound implications for what we should do in every home and school.
The stimulation young children receive from early interactions determines how their brains develop in the crucial postnatal period, when experiences have a decisive impact on the brain’s architecture and later capabilities. Brain cells create connections each time we integrate something new. Whether we are learning to crawl or dance, these experiences create brain pathways that capture what we know and who we are.
In its early years, the brain goes on a connectivity binge. The immature brain quickly links hundreds of millions of neurons together, forming efficient brain circuits. During these stages, children make learning look easy. By adding, removing, or changing the strength of the connections among neurons, linking cells together or eliminating brain cells from existing neural pathways, neuronal activations change, making specific new learning possible. The word specific must be underscored here. All learning must be specific and transferable if it is to have any currency.
Creating new neural pathways is physically exhausting. The infant brain requires near-constant feeding to keep up with the energy consumption necessary for early brain development. Infants tax their energies when they are learning how to walk, talk, think, speak and remember, along with familiarizing themselves with all of the people, places and objects in their environment. Toddlers must also learn the complexities of language, and must master critical cultural and socialization skills. All of these are the minimum challenges that must be successfully and simultaneously met for adaptation to the environment. Synaptic connectivity maxes out during the second year of life. At its peak level, each neuron averages 15,000 connections. That number occurs in the early years of child development, when a toddler’s brain consumes 225% of the energy of an adult brain.
Enrichment studies have shown that a caring environment aids learning and development. But neuroplasticity also has a darker side. Impoverished environmental conditions, prenatal substance exposure, sensory deprivation, emotional trauma and nutritional deficiencies can cause plasticity to play its unkind hand, wreaking havoc on the developing young brain. Long-term chronic stress (“toxic stress”) provokes the release of high levels of the hormone cortisol that can lead to permanent damage to hippocampal neurons, causing learning difficulties and memory impairments.
On the brighter side, the human brain responds favorably to emotional support, challenge and steady constructive—it need not always be positive—feedback by increasing the myelination and nourishment of neural pathways. Individuals who are blind at birth have highly resilient brains eager to compensate for any deficiency. With their acute hearing ability, some of the world’s best musicians have emerged among the blind. In the absence of appropriate stimulation, the brain reassigns underutilized areas for other, sometimes completely different, functions.
Failure is not an option is a popular educational mantra that was unwisely borrowed from the business world. It inaccurately reflects how the young human brain learns. Students who struggle in school often appear to be impervious to the best efforts of well-trained professionals. The notion of “rigor” becomes almost academic rigor mortis for them. In nearly all cases, each learning difficulty is indicative of a neurological underinvestment in the necessary brain wiring needed to be successful. When we point to a concept or skill that is not “developmentally appropriate,” the reference we are making is to brain development, not curriculum development.
With this backdrop, certain academic shortcomings are expected. However, these events foster frustrations when the child “doesn’t get it.” With time, maturation and the appropriate brain wiring, s/he will one day “get it.” When it comes to learning, failure is often a prerequisite. This is particularly true when learners lack related prior experiences, as the new information cannot merge with brain circuits that don’t exist yet. When there is nothing with which to integrate new knowledge, the building process must begin from scratch. The child is not “slow”; the process of brain-building is sometimes slow.
In Outliers: The Story of Success, author Malcolm Gladwell hypothesizes that exceptional performances in any field have little to do with innate talent. He proposes the “10,000-Hour Rule”: devoting approximately 10,000 hours of time to a skill fosters a dendritic density representing competency in that area. Whether we are examining achievement in academics, professional careers, athletics or public speaking, practice makes permanent, not perfect, when it comes to the human brain.
Long years of continuous practice create the hard-wired neural pathways of proficiency and expertise. Complex interconnections among the pathways in the brain give an expert four distinct neurological advantages:
1. Highly used neural pathways are easily activated, because they are nearly always “on alert.”
2. Extensive hardwiring provides neural “shortcuts” to answers that their under-wired counterparts might find puzzling for hours, days, years or forever.
3. Their jam-packed cognitive tool chest serves as a repository of information, precluding the time-consuming data searches required by others.
4. Most importantly, cognitive resources are freed up to engage in ideational exploration and conceptual processing. The question asked about experts such as golfer Tiger Woods changes from “Is he any good?” to “Is he always that good?”
Experts routinely take the time to learn, unlearn and relearn relevant information related to their craft. For them, learning is not an informing experience, where they simply build networks to represent their new experiences; instead, their experience is transforming: Their brain circuits are rearranged in order to integrate new data.
The Future of the Brain
With each major advance in the human condition over the past 4.5 million years, our brain volume has increased to accommodate our behavioral improvisations. Is the human brain on the doorstep of another “brain spurt”? Our evolutionary history would suggest that we may be. The remarkable world of technology will likely be accommodated by an even more remarkable brain plasticity.
As we come to the close of the first decade in the 21st Century, we recognize that we are living in a unique, historic time. Neuroplasticity is shaping today’s young brains for a future that is less like our recent past than any other time in human history. Technology is extending the range of human information processing, shattering the previous limitations of our sensory systems. Previously, the walls of time and place dictated the scope of the human experience. These barriers are falling rapidly.
If you are a parent, educator, or anyone charged with the responsibility of developing young minds, brain literacy is no longer optional. When you are asked by your former students, children or grandchildren, What did you do to help me when that new research on the brain suddenly became accessible to you?, hopefully, your answer will be, I did everything I could, based on everything we knew from every field in neuroscience at that time.
Kenneth Wesson 2010