Conjoined Twins and Split Brain Patients
As often is the case in science, the study of unique phenomenon can provide a wealth of knowledge and information about normal occurrences. This is true with regard to case studies of both split brain patients and conjoined twins. The unique experiences of these patients have contributed a great deal to our understanding of how the brain functions in a range of both normal and extraordinary circumstances.
Split brain patients are people who have had surgery to cut the corpus callosum, which you may recall, is the main pathway connecting the two halves of the cortex. Often this procedure was done to alleviate symptoms of epilepsy. These patients acted normal enough so that for the first few years after such surgeries were performed, physicians reported that there were no consequences of the procedure. Over the years, however, careful behavioral studies revealed that these patients appeared to have two minds at work in one body. One mind, mediated by the left hemisphere, could talk and respond to questions, while the other mind, in the right hemisphere, could only communicate by gestures and action. Remarkably, the left brain seemed to be unaware that another mind controlled half of the body.
In the case of dicephalic parapagus conjoined twins, (twins who share a body but have separate brains) it is clear that there are two minds because there are two separate brains and each of them can communicate. In craniopagus conjoined twins, there are two separate bodies but a shared brain or portions of brain.
The range of behavior, from relatively normal to unique, of split brain patients and conjoined twins raises questions about what it means to be a “person.” For this week’s Discussion, you compare and contrast split brain patients and conjoined twins, and explore what “personhood” means in light of what these patients can teach us about the brain and its functions.
With these thoughts in mind:
Explain how split-brain patients demonstrate the organization of the brain. Then, describe two similarities and two differences between split brain patients and conjoined twins. Finally, define “personhood” in your own words as it relates to split brain patients or conjoined twins and use the current literature to support your definition.