The human brain is composed of approximately 100 billion neurons. Early researchers believed that neurogenesis, or the creation of new neurons, stopped shortly after birth. Today, it is understood that the brain possesses the remarkable capacity to reorganize pathways, create new connections and, in some cases, even create new neurons. This is part of the amazing process called brain plasticity. What? Brain plasticity, also known as neuroplasticity or cortical remapping, is a term that refers to the brain’s ability to change and adapt as a result of experience.
Up until the 1960s, researchers believed that changes in the brain could only take place during infancy and childhood. By early adulthood, it was believed that the brain’s physical structure was permanent. Modern research has demonstrated that the brain continues to create new neural pathways and alter existing ones in order to adapt to new experiences, learn new information and create new memories. This is especially promising when it comes to traumatic brain injury, brain cancer, or other physiological problems.
There are four key facts about neuroplasticity. First, it can vary by age. While plasticity occurs throughout the lifetime, certain types of changes are more predominant during specific ages. Second, it involves a variety of processes. Plasticity is ongoing and involves brain cells other than neurons, including glial and vascular cells. A glial cell is a supportive cell in the central nervous system. Unlike neurons, glial cells do not conduct electrical impulses. The glial cells surround neurons and provide support for and insulation between them. Glial cells are the most abundant cell types in the central nervous system. Types of glial cells include oligodendrocytes, astrocytes, ependymal cells, Schwann cells, microglia, and satellite cells.
We know the first few years of a child’s life are a time of amazing brain growth. This, of course, is why many psychologists speak often on the importance of these so-called formative years. At birth, every neuron in the cerebral cortex has an estimated 2,500 synapses; by age of three, this number has grown to a whopping 15,000 synapses per neuron. Interestingly, the average adult has about half that number of synapses. Why? Because as we gain new experiences, some connections are strengthened while others are eliminated. This process is known as synaptic pruning. Neurons that are used frequently develop stronger connections and those that are rarely or never used eventually die. By developing new connections and pruning away weak ones, the brain is able to adapt to the changing environment. Synaptic pruning refers to the process by which extra neurons and synaptic connections are eliminated in order to increase the efficiency of neuronal transmissions. The entire process continues up until approximately ten years of age, by which time nearly fifty percent of the synapses present at two years of age have been eliminated. The point of this process is to improve the efficiency of the neurological system.
Neuroplasticity refers to changes in neural pathways and synapses due to changes in behavior, environment, neural processes, thinking, and emotions – as well as to changes resulting from bodily injury. This discovery has lead to new approaches in physical and occupational therapy. Although it takes patience and time, it is possible through therapy, and through the use of various cognitive challenges, to begin to rewire the brain. There is a claim that’s been around for decades which indicates we use only about ten percent of our brain. There is no scientific evidence that this is true. According to the believers of this myth, if we used more of our brain, then we could perform super memory feats and have other fantastic mental abilities – maybe we could even move objects with a single thought. Who knows what abilities there are hiding in the remaining ninety percent?
Certainly there are numerous pathways that serve similar functions. For example, there are several central pathways that are used for vision. This concept is called “redundancy” and is found throughout the nervous system. Multiple pathways for the same function may be a type of safety mechanism should one of the pathways fail. Still, functional brain imaging studies show that all parts of the brain function. Even during sleep, the brain is active. The brain is still being “used,” it is just in a different active state. It seems reasonable to suggest that if ninety percent of the brain was not used, then many neural pathways would degenerate. However, this does not seem to be the case. The popular notion that large parts of the brain remain unused, and could subsequently be “activated”, rests in popular folklore and not science. Though mysteries regarding brain function remain—e.g. memory, consciousness—the physiology of brain mapping suggests that all areas of the brain have a function. Frankly, we use one hundred percent of our brain.
If ninety percent of the brain is normally unused, then damage to these areas should not impair performance. Instead, there is almost no area of the brain that can be damaged without loss of abilities. Even slight damage to small areas of the brain can have profound effects. Brain scans have shown that no matter what one is doing, all brain areas are always active. Some areas are more active at any one time than others, but barring brain damage, there is no part of the brain that is absolutely not functioning. Technologies such as positron emission tomography (also known as PET) and functional magnetic resonance imaging (fMRI) allow the activity of the living brain to be monitored. They reveal that even during sleep, all parts of the brain show some level of activity. Only in the case of serious damage does a brain have “silent” areas.
The 2014 film Lucy, starring Morgan Friedman and Scarlet Johansson, depicts a character who gains increasingly godlike abilities once she surpasses ten percent – though the film suggests ten percent represents brain capacity at a particular time rather than permanent usage. The human brain is complex. Along with performing millions of mundane acts, it composes concertos, issues manifestos and comes up with elegant solutions to equations. It’s the wellspring of all human feelings, behaviors, experiences as well as the repository of memory and self-awareness. So it’s no surprise that the brain remains a mystery unto itself.
I believe the myth that we use only ten percent of our brain stems from people’s conceptions about their own brains. They see their own shortcomings as evidence of the existence of untapped gray matter. This is a false assumption. What is correct, however, is that at certain moments in anyone’s life, such as when we are simply at rest and thinking, we may be using only ten percent of our brains, but we are not limited to using only one-tenth of our brain. The brain has an extraordinary ability modify its own structure and function following changes within the body or in the external environment. The large outer layer of the brain, known as the cortex, is especially able to make such modifications.
Brain plasticity underlies normal brain function such as our ability to learn and modify our behavior. It is strongest during childhood — explaining the fast learning abilities of kids — but remains a fundamental and significant lifelong property of the brain. Adult brain plasticity has been clearly implicated as a means for recovery from sensory-motor deprivation, peripheral injury, and brain injury. It has also been implicated in alleviating chronic pain and the development of the ability to use prosthetic devices such as robotic arms for paraplegics, or artificial hearing and seeing devices for the deaf and blind.
In recent years, brain plasticity has been implicated in the relief of various psychiatric and neurodegenerative disorders both in humans and in animals. These disorders include obsession, depression, compulsion, psychosocial stress, Alzheimer’s disease, and Parkinson’s disease. Furthermore, recent research suggests that the pathology of some of these devastating disorders is associated with the loss of plasticity. Collectively, there is a growing recognition that brain plasticity plays a fundamental role in either the deterioration to, or the alleviation of, psychiatric and degenerative brain disorders.