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, What is Going in There?
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 (See Chart 1: Neuroplasticity). 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 — color, 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 (See Chart 2: 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.