Causes Brain Plasticity
From Barbaric to Elegant
Originally brain plasticity was defined as the ability to reorganize after injury. Fairly barbaric yet incredibly informative studies looked at how cats responded to brain injury. One of the causes of brain plasticity resulted when scientists removed ever larger sections of the cats' motor cortex. The brain reorganized so that cats were eventually able to walk again. Modern experiments show that simple electrical stimulation causes brain plasticity. From the earliest experiments until the present, the definition of brain plasticity and its causes has come to encompass many things.
Stimulating Brain Plasticity
Brain plasticity was understood to mean the relative strengthening of certain connections in the brain, called synapses, or an increase or decrease in the number of synaptic connections. When new information is learned, it causes brain plasticity since connections are added or strengthened. In fact one of the ways that neuroscientists study memory formation is by using long term potentiation or LTP. By administering a rapid and strong set of electrical stimuli, connections are strengthened which, in essence, causes brain plasticity. Scientists study LTP as a cellular correlate of how new memories from in the brain.
I Can Make New Neurons?
For a long time it was believed that once neurons in the brain were formed early in life, no more were made. If neurons died, that was it, they were gone. While for many brain regions that is still the case, there are certain areas of the brain that actually continue to make new neurons throughout life. This birth of new neurons is a form of brain plasticity. Scientists are aggressively studying the causes of this brain plasticity so that they can perhaps someday treat spinal cord injuries or neurodegenerative diseases like Alzheimer's and Parkinson's diseases.
Another interesting phenomenon is that of phantom limbs. The phantom limb phenomenon often occurs in people who have lost a limb through an accident or surgical amputation. Despite the fact that there is no longer a limb present, patients routinely report that they feel that their limb is still there. Sadly, they often find this "phantom limb" to be quite tender or painful. Note that this is different than pain at the edge of the remaining skin-the person actually feels that the limb is still there. This is situation eventually causes brain plasticity as the brain learns that there is no longer a limb present.
One ingenious experiment shows how our brain is rapidly able to adapt to strange stimuli. Wolfgang Kohler had subjects wear a special pair of glasses in which the lenses were prisms. These prisms inverted everything that was seen. What was up was down and down was up. The first few days of wearing this glasses were challenging as people had trouble getting around. After a few days however, they began to adjust and could do daily activities. Some could eventually ski or ride a bike! Wearing the glasses actually causes brain plasticity. How do we know? When the subjects stopped wearing the glasses, they did not immediately go back to normal but needed to adjust. Thus taking off the glasses causes brain plasticity, too!
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