With my maternal uncle hospitalised for a brain disorder, I spent few hours of this weekend in the hospital. It proved to be a brain opener for me. I had a little chat with my brother-in-law, who is doctor with MD (Gen). The inquistive questioning in me came to help and I really learned a lot from it.
The human brain is divided into two hemispheres (halves). The Left vs Right and each halves specializing in certain activities. Check out the comparison chart over here.
With the disorder in left part of the brain, my uncle has lost control over the right part of his body. His speech and languages tends to get affected. But still he would be able to retain his mother-tongue. Nature is really amazing.
More links about Left vs Right brain