Hemispherectomy Reading
The hemispherectomy provides a vivid example of brain plasticity. Dating back to 1928, the hemispherectomy was devised as a treatment for malignant brain tumors. However, not only did it fail to cure the patients, but it was also associated with high mortality and morbidity. The surgery was used again in the 1940s and 1960s as a treatment for seizure disorders, but each time it fell into disfavor because of postoperative complications.
A number of medical advancements have contributed to its more recent success. As the text indicates, one Johns Hopkins medical team, which has followed up on the 58 child hemispherectomies they have performed, are "awed" by how well the children retain their memory, personality, and humor after removal of either hemisphere. The most dramatic change is a positive one. The children are happier. Jason Brandt, Johns Hopkins neurologist, concludes, "That a child with half a brain can indeed be a whole person speaks to the malleability of both the human brain and human spirit. It's amazing, it's wonderful. I'm at a loss to describe it."
Surely some drawbacks will always remain. For example, some neurological functions do not transfer from one hemisphere to the other. All the "hemis" remain blind in one-half of each eye. They also continue to have some degree of paralysis on one side of their bodies. Fine motor movement is lost in one hand. In general, the effect of removing one hemisphere is inversely related to the age of the child at the time of surgery. If performed early enough, the surgery does not seem to cause deficits in higher mental functions in adulthood. Two different theoretical conclusions have been drawn from this finding. One is that no shift from one hemisphere to the other has occurred because lateralization of function is not present in early infancy. The other is that hemispheric differences are present very early in life, but the young brain has the ability to reorganize itself in the face of damage to specific areas. Recent studies comparing the abilities of persons with left and right hemispherectomies suggest that the latter plasticity explanation is more likely to be correct.
For example, research on those who had hemispherectomies (some in the first few months of life) indicate that those who have had the left hemisphere removed have some continuing difficulty with both syntax and the processing of speech sounds. When asked to judge the acceptability of the three sentences "I paid the money by the man," "I was paid the money to the lady," and "I was paid the money by the boy," those who had had the left hemisphere removed failed to recognize the first two as grammatically incorrect. The researchers concluded that the right hemisphere does not accurately comprehend the meaning of passive sentences. There are limits to the plasticity of the infant brain, and some hemispheric differences seem to be present very early in life.
Springer, S., & Deutsch, G. (1998). Left brain, right brain (5th ed.). New York: W. H. Freeman.