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The Evolution of Neuroplasticity

The notion of “neuroplasticity,” that is the ability of the human brain to repair and rewire after injury or change in function, has undergone dramatic changes in the last 120 years. As early as the late 1800’s the father of modern psychology, William James, wrote extensively on the notion of neuroplasticity of the brain and quite accurately for his time. Starting in the earlier 20th century, scientists looked even closer at the brain and this notion, oddly, changed. The work of Ramon y. Cajal and others began to show structural areas of the brain that have never been described before. Further research was able to tie these newly discovered brain structures to specific functions in the human body. From this point, the 1920’s to almost the late 1990’s, the idea that the brain could significantly alter itself after injury or produce new brain cells was a lost idea. We all grew up with the idea that “You are born with a number of brain cells and then they begin dying.”

In the last twenty years amazing findings regarding the neuroplasticity of the brain have been published, including:

  • Taxi cab drivers after being forced to learn thousands of addresses in London, for purposes of training, developed larger areas of the brain known as the hippocampus, which is associated with memory;
  • The hippocampus in the olfactory areas of the brain were constantly producing new neurons though out our lives;
  • Children under six who undergo, unfortunately, a hemiectomy, whereby one half of their brain is taken out, are able to regain almost normal function because of the brain’s ability to rewire and literally take over the functions of the missing other half of the brain. There are limitations to this. For example, in a child who’s brain had managed to move control of a function to a new part of the brain because of the surgery, it was found that he was almost unable to learn any mathematics because the area of the brain where mathematics was learned had been occupied by another function after the surgery;
  • There are two types of stem cells in the human brain that can be activated for a number of reasons including injury, and can take the form and function of the missing brain matter and make repairs known as neuroregeneration. It is likely that neuroregeneration will be found to occur in all areas of the brain in the next ten years. However, it obviously does not occur at a scale where miraculous recovery from catastrophic injury can occur. Therapies and future modalities might be able to tease these cells into doing more repairs in the future.

So at the present time the brain science neuroplasticity is back in and is being talked about in thousands of studies a year. We now know that some of the plasticity, for example, in learning languages, ends at a very early age. Dr. Jeffery Schwartz in his fascinating recent book “The Mind and The Brain: Neuroplasticity and the Power of Mental Force” describes many interesting examples of neuroplasticity. It has been shown for example, that very young children of the age of two can understand and hear all of the many sounds in every language in the world. That is why language acquisition is spectacularly easy if it is done at a young age and is significantly harder as we age. Studies in Japanese adults, whereby they were asked to listen to certain English language sound, were literally unable to hear some of those sounds at all, as if they did not exists.

The young brain also responds quite adversely to lack of use. It has been shown that there is a crucial three month period in many mammals whereby if they are kept in a dark room or otherwise unable to use their eyes, that proper connections between the brain and the eye simply do not form and permanent blindness is a result. However, when there are areas in the brain that are under utilized or not utilized at all because of the lack of hearing, vision or other sensory input, that area is taken over by nearby parts of the brain and recruited to do work for them. Thus, nothing is wasted.

In a 2011 Wall Street Journal article, they described findings that show teenagers intellects and IQ can rise or fall as many as 20 points in just a few years. This is certainly contrary to the thinking of the last hundred years. These changes are consistent with other findings, where scientists have determined that experience can easily alter the brain and its networks of billions of neural synapses. This is consistent with some of the tenets of the relatively new concept of “Cognitive Reserve” whereby persons going through life with more active and stimulating everyday lives are more able to fend off the ravages of old age dementia and Alzheimer’s. All of these new findings put a ball squarely in each person’s court – you can alter your brain for the better and as the past President of the American Psychological Association noted “Those who are mentally active will likely benefit. The couch potatoes among us, who do not exercise themselves intellectually, will pay a price.”

While many of these findings are good news for those who have suffered brain injury, a widespread or diffuse brain injury caused by a high speed collision, for example, is currently resistant to full recovery. “Focal” or specifically located injuries are much easier for the brain to readapt and deal with. Also, unfortunately for the moderate to severely brain injured, the likelihood of becoming a couch potato because of their injury, will likely have the effect of decreasing the likelihood of positive brain restructuring through life and will result in the injured falling further and further behind their peers.