What Is Brain Plasticity?

Brain plasticity from learning
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Brain plasticity, also known as neuroplasticity, is a term that refers to the brain's ability to change and adapt as a result of experience. When people say that the brain possesses plasticity, they are not suggesting that the brain is similar to plastic. Neuro represents neurons, the nerve cells that are the building blocks of the brain and nervous system, and plasticity refers to the brain's malleability.

 

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 mostly 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.

History and Research on Brain Plasticity

Psychologist William James suggested that the brain was perhaps not as unchanging as previously believed way back in 1890. In his book The Principles of Psychology, he wrote, "Organic matter, especially nervous tissue, seems endowed with a very extraordinary degree of plasticity." However, this idea went largely ignored for many years.

In the 1920s, researcher Karl Lashley provided evidence of changes in the neural pathways of rhesus monkeys. By the 1960s, researchers began to explore cases in which older adults who had suffered massive strokes were able to regain functioning, demonstrating that the brain was much more malleable than previously believed.

Modern researchers have also found evidence that the brain is able to rewire itself following damage.

In his book The Brain that Chances Itself: Stories of Personal Triumph from the Frontiers of Brain Science, Norman Doidge suggests that this belief that the brain was incapable of change primarily stemmed from three major sources.

First was the ancient belief that the brain was much like an extraordinary machine, capable of astonishing things yet incapable of growth and change. Second was the observation that people who had suffered from serious brain damage were often unable to recover. Finally, the inability to actually observe the microscopic activities of the brain played a role in the idea that the brain was relatively fixed.

Thanks to modern advances in technology, researchers are able to get a never-before-possible look at the brain's inner workings. As the study of modern neuroscience flourished, researchers demonstrated that people are not limited to the mental abilities they are born with and that damaged brains are often quite capable of remarkable change.

How Does Brain Plasticity Work?

The human brain is composed of approximately 86 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.

There are are a few defining characteristics of neuroplasticity:

  1. It can vary by age. While plasticity occurs throughout the lifetime, certain types of changes are more predominant during specific life ages. The brain tends to change a great deal during the early years of life, for example, as the immature brain grows and organizes itself. Generally, young brain's tend to be more sensitive and responsive to experiences than much older brains.
  2. It involves a variety of processes. Plasticity is ongoing throughout life and involves brain cells other than neurons, including glial and vascular cells.
  3. It can happen for two different reasons. As a result of learning, experience, and memory formation, or as a result of damage to the brain. While people used to believe that the brain became fixed after a certain age, newer research has revealed that the brain never stops changing in response to learning. In instances of damage to the brain, such as during a stroke, the areas of the brain associated with certain functions may be damaged. Eventually, healthy parts of the brain may take over those functions and the abilities can be restored.
  4. Environment plays an essential role in the process. Genetics can also have an influence. The interaction between the environment and genetics also plays a role in shaping the brain's plasticity.
  5. Brain plasticity is not always good. Brain changes are often seen as improvements, but this is not always the case. In some instances, the brain might be influenced by psychoactive substances or pathological conditions that can lead to detrimental effects on the brain and behavior.

Types of Brain Plasticity

  • Functional Plasticity refers to the brain's ability to move functions from a damaged area of the brain to other undamaged areas.
  • Structural Plasticity refers to the brain's ability to actually change its physical structure as a result of learning.

The first few years of a child's life are a time of rapid brain growth. At birth, every neuron in the cerebral cortex has an estimated 2,500 synapses; by the age of three, this number has grown to a whopping 15,000 synapses per neuron.

The average adult, however, 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.

References

Doidge, Norman (2007). The Brain That Changes Itself: Stories of Personal Triumph from the frontiers of brain science. New York: Viking.

Gopnic, A., Meltzoff, A., Kuhl, P. (1999). The Scientist in the Crib: What Early Learning Tells Us About the Mind, New York, NY: HarperCollins Publishers.

Kolb, B., & Gibb, R. (2011). Brain plasticity and behavior in the developing brain. Journal of the Canadian Academy of Child and Adolescent Psychiatry. 20(4), 265-276.

Hockenbury, D., & Hockenbury, S. E. (2007). Discovering Psychology. New York, NY: Worth Publishers.

Neuroscience for Kids. (n.d.) Brain plasticity: What is it. http://faculty.washington.edu/chudler/plast.html

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