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Stroke Smart Magazine


July/August 2007
AMAZING BRAIN

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Right vs. Left: What Does It Mean?


By Jay Schneiders, PhD


The human brain is divided into two sides or hemispheres. The right side of the brain is often said to be the creative side. Artists tend to say they are “right brained." The left side is thought to be the more analytical side. Bankers and math whizzes may describe themselves as “left brained."


Although there is some truth to this basic formula, it simplifies the story. Each side of the brain does influence different functions differently. But different people's brains do this in rather different ways.


For example, let's look at speech and language, which tend to be more strongly influenced by the left side of the brain. When tests are done to shut down the left half of the brain, about 98 percent of right-handed people will have a significant problem with language and speech. Similarly, about 70 percent of left-handers will also have a major speech problem when the left side is turned off. For the others, there will be a significant disruption of speech when either side of the brain is turned off, or sometimes only when the right side is.


What does this mean? Most importantly it shows us how variable and complex the brain really is. In the case of tasks such as talking, listening, reading and writing, both sides of the brain constantly communicate and work together no matter what we think, feel or do.


Still, the left side of the brain does process information differently from the right side. This is especially important to stroke survivors who have had a stroke on one side of the brain or the other.


The left side of the brain (again, in most, but not all of us) deals with putting information in order and analyzing things in a more sequential way. It handles details, is (in some ways) superior for reading and writing, and is probably more responsible for positive emotions such as joy. People with left-sided strokes may have trouble with skilled movements, depression and speech.


In contrast, the right side of the brain has a more big-picture, large-scale processing style. It pulls information together, seems better at handling new information, and is probably more responsible for negative feelings. People with right-sided strokes may have problems with music, melody in speech, confusion and anxiety reactions.


It is also important to consider whether a stroke has affected the front or back of the brain. For example, strokes affecting the front of the brain tend to affect the ability to recall verbs. Conversely, strokes that occur in the back of the brain may cause problems recalling nouns. And strokes affecting the back of the brain (on either side) tend to disrupt the way we make sense of what our eyes (and various other senses) perceive.


For the stroke survivor the complexity of the brain can be good, but also frustrating, news. It's beneficial that multiple brain regions are involved in every human function and experience. This is because stroke damages specific areas of the brain, leaving others intact and sometimes able to take over some lost function. But that same complexity makes every patient's symptoms so often seem to be “exceptions to the rule” — hard for clinicians to pin down, assess with precision and predict with accuracy.


Neuropsychologists approach evaluations of patients' brains after stroke with the general differences between the left and right hemispheres in mind. But we are also aware that the brain is far too complicated and elegant an organ to be reduced to such simple terms. It is this very fact that enables us in stroke rehabilitation to work so hard for and hopefully with stroke survivors to mobilize different parts of the brain to try to compensate for damage that may have occurred primarily on one side or the other.



 

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