06 Nov WHAT IS NEUROPLASTICITY, ANYWAY?
Read why Functional Neurology is so effective!
John Lieurance, D.C.
WHAT IS NEUROPLASTICITY, ANYWAY?
The human brain is incredibly adaptive. Our mental capacity is astonishingly large, and our ability to process widely varied information and complex new experiences with relative ease can often be surprising. The brain’s ability to act and react in ever-changing ways is known, in the scientific community, as “neuroplasticity.” This special characteristic allows the brain’s estimated 100 billion nerve cells, also called neurons (aka “gray matter”) and depicted in the image below, to constantly lay down new pathways for neural communication and to rearrange existing ones throughout life, thereby aiding the processes of learning, memory, and adaptation through experience. Without the ability to make such functional changes, our brains would not be able to memorize a new fact or master a new skill, form a new memory or adjust to a new environment; we, as individuals, would not be able to recover from brain injuries or overcome cognitive disabilities. Because of the brain’s neuroplasticity, old dogs, so to speak, regularly learn new tricks of every conceivable kind.
WHAT PARTS OF THE BRAIN HAVE PLASTICITY?
Plasticity Happens Wherever Neuro-processing Occurs
Neuroplasticity is not a trait found in a single brain structure, nor does it consist of just one simple type of physical or chemical event. Rather, the brain’s ability to be molded – its plasticity – is the result of many different, complex processes that occur in our brains throughout our lifetime. However, it is demonstrated starkly in the process of brain development in the first two years of life. A baby spends first two years growing neuronal connections, called synapses – many millions A SECOND – and also busily pruning them. Only those synapses that are stimulated by experience or practice will be preserved – the rest will be eliminated. All of our experiences, knowledge and understanding are encoded in the brain by a pattern of synapse strengths. A host of different structures and types of cells play some part in making neuroplasticity possible. There are even different types of plasticity that, depending on one’s age, are more or less involved in reshaping the brain as it handles new information. Plasticity works throughout the brain not just in the normal processes of learning and adaptation (most obvious in the early developmental years, though continuing throughout life), but also in response to injuries or diseases that cause loss of mental functioning.
NEUROPLASTICITY AND THE NATURE/NURTURE DEBATE: WHICH IS IT?
On The One Hand There’s Nature, On The Other, Nurture.
While genetics certainly play a role in establishing the brain’s plasticity, the environment also exerts heavy influence in maintaining it. Take, for example, the newborn’s brain, which every day is flooded with new information. When the infant body receives input through its many different sensory organs, neurons are responsible for sending that input back to the part of the brain best equipped to handle it – and this requires each neuron to “know” something about the proper neural pathways through which to send its bits and pieces of information. To make this mental roadmap work, each neuron develops an axon to send information to other brain cells via electrical impulses, and also develops many dendrites that connect it to other neurons so that it can receive information from them. Each point of connection between two neurons is termed a “ synapse.” Our genes have, at birth, laid down the basic directions for neurons to follow along this roadmap, and have built its major “highways” between the basic functional areas of the brain. Environmental influence then plays the key role in forging a much denser, more complex network of interconnections. These smaller avenues and side roads, always under construction, can make the transfer of information between neurons more efficient and rich with situation-specific detail. This is clearly evidenced by the rapid increase in synaptic density that can be seen in a normally developing human. Genetics form a neural framework that, at birth, starts each neuron off with roughly 2,500 connections. By age two or three, however, sensory stimulation and environmental experience have taken full advantage of the brain’s plasticity; each neuron now boasts around 15,000 synapses. This number will have declined somewhat by the time we enter adulthood, as many of the more ineffective or rarely used connections – formed during the early years, when neuroplasticity is at its peak — are done away with.
HOW DOES NEUROPLASTICITY WORK?
A Matter Of Neuron Networks And Connections.
Neuroplasticity can work in two directions; it is responsible for deleting old connections as frequently as it enables the creation of new ones. Through this process, called “synaptic pruning,” connections that are inefficient or infrequently used are allowed to fade away, while neurons that are highly routed with information will be preserved, strengthened, made even more synaptically dense. Closely tied in with the pruning process, then, is our ability to learn and to remember. While each neuron acts independently, learning new skills may require large collections of neurons to be active simultaneously to process neural information; the more neurons activated, the better we learn.
DOES NEUROPLASTICITY HELP ME LEARN AND REMEMBER?
Remolding Connections Through Synaptic Transmission.
Learning affects the brain in two different ways, neither of which would be possible without the special plasticity of our brains. In response to a new experience or novel information, neuroplasticity allows either an alteration to the structure of already-existing connections between neurons, or forms brand-new connections between neurons; the latter leads to an increase in overall synaptic density, while the former merely makes existing pathways more efficient or suitable. In either way, the brain is remolded to take in this new data and, if useful, retain it. While the precise mechanism that allows this process to occur is still unclear, some scientists theorize that long-term memories are formed successfully when something called “reverbration” occurs. When we are first exposed to something new, that information enters our short-term memory, which depends mostly upon chemical and electrical processes known as synaptic transmission to retain information, rather than deeper and more lasting structural changes such as those mentioned above. The electrochemical impulses of short-term memory stimulate one neuron, which then stimulates another; the key to making information last, however, occurs only when the second neuron repeats the impulse back again to the first. This is most likely to happen when we perceive the new information as especially important or when a certain experience is repeated fairly often. In these cases, the neural “echo” is sustained long enough to kick plasticity into high gear, leading to lasting structural changes that hard-wire the new information into the neural pathways of our brains. These changes result either in an alteration to an existing brain pathway, or in the formation of an all-new one. In this way, the new information or sensory experience is cemented into what seems, at its present moment, to be the most useful and efficient location within the massive neurocommunication network. Further repetition of the same information or experience may lead to more modifications in the connections that house it, or an increase in the number of connections that can access it – again, as a result of the amazing plasticity of our brains.
THE DAMAGED OR DISABLED BRAIN: CAN NEUROPLASTICITY HELP?
Rebuilding Connections That Rebuild Skills.
Neuroplasticity is the saving grace of the damaged or disabled brain; without it, lost functions could never be regained, nor could disabled processes ever hope to be improved. Plasticity allows the brain to rebuild the connections that, because of trauma, disease, or genetic misfortune, have resulted in decreased abilities. It also allows us to compensate for irreparably damaged or dysfunctional neural pathways by strengthening or rerouting our remaining ones. While these processes are likely to occur in any number of ways, scientists have identified four major patterns of plasticity that seem to work best in different situations. Take, for example, the case in which healthy cells surrounding an injured area of the brain change their function, even their shape, so as to perform the tasks and transfer the signals previously dealt with by the now-damaged neurons at the site of injury. This process, called “functional map expansion,” results in changes to the amount of brain surface area dedicated to sending and receiving signals from some specific part of the body. Brain cells can also reorganize existing synaptic pathways; this form of plasticity, known as a “compensatory masquerade,” allows already-constructed pathways that neighbor a damaged area to respond to changes in the body’s demands caused by lost function in some other area. Yet another neuroplastic process, “homologous region adoption,” allows one entire brain area to take over functions from another distant brain area (one not immediately neighboring the compensatory area, as in functional map expansion) that has been damaged. And, finally, neuroplasticity can occur in the form of “cross model reassignment,” which allows one type of sensory input to entirely replace another damaged one. Cross-model reassignment allows the brain of a blind individual, in learning to read Braille, to rewire the sense of touch so that it replaces the responsibilities of vision in the brain areas linked with reading. One or several of these neuroplastic responses enable us to recover, sometimes with astonishing completeness, from head injury, brain disease, or cognitive disability.
NEUROPLASTICITY CAN’T LAST FOREVER . . . CAN IT?
From Fresh Experiences Throughout Your Lifetime.
Contrary to widespread belief, the “garden” of the brain never ceases being pruned and newly planted. Though long believed by scientists to be the case, research over the past decade or so has proven that our neural connections do not ever reach, by some age, a fixed pattern that thereafter cannot change. Rather, the ongoing process of synaptic reformation and death is what gives the brain its plasticity – its ability to learn and remember, to adapt to its environment and all the challenges brought with it, to acquire new knowledge and learn from fresh experiences – throughout an individual’s lifetime. Groundbreaking new research suggests that, beyond modifying pathways and forming new ones between existing neurons, the human brain is even able to generate entirely new brain cells. While this neural regeneration was long believed to be impossible after age three or four, research now shows that new neurons can develop late into the life span, even into the golden years of age 70 and beyond. Thus, the old adage “use it or lose it” is brought soundly home. If one’s brain is constantly challenged by and engaged with a variety of stimulations and new experiences, while also exposed regularly to that which it already knows, it is better able to retain its adaptive flexibility, regenerative capacity, and remarkable efficiency throughout life.
WHAT DIRECTIONS MIGHT NEUROPLASTICITY TAKE IN THE FUTURE?
Seeking A World Without Mental Health Issues.
Current research suggests that neuroplasticity may be key to the development of many new and more effective treatments for brain damage, whether resulting from traumatic injury, stroke, age-related cognitive decline, or any number of degenerative diseases (Alzheimer’s, Parkinson’s, and cerebral palsy, among many others). Plasticity also offers hope to people suffering from cognitive disabilities such as ADHD, dyslexia, and Down Syndrome; it may possibly lead to breakthroughs in the treatment of depression, anorexia, and other behavioral and emotional disorders as well. Some scientists have even ventured to suggest that, one day, neuroplasticity could be used in short-circuiting the brain’s racist, sexist, or otherwise culturally unacceptable thinking patterns; even the body’s ability to perform intricate sequences of activities necessary for sports and other highly complex physical processes might eventually be perfected through the power of neuroplasticity. Whether currently in use or only the product of futuristic hopes, the theory upon which harnessing the brain’s plasticity is based is a relatively simple one. With “directed neuroplasticity,” scientists and clinicians can deliver calculated sequences of input, and/or specific repetitive patterns of stimulation, to cause desirable and specific changes in the brain. As further research reveals the best ways to create and direct these stimuli, the amazing potential of the brain’s plasticity can begin to be taken advantage of in medicine, mental health, and a wealth of as-yet-uncharted territory in human behavior and consciousness. Thus, increasing our understanding of neuroplasticity holds great promise – through its complex workings skills lost can be relearned; the decline of abilities can be staved off, even reversed; and entirely new functions can even, perhaps, be gained.