Learning from Brain Damaged Individuals

Abstract

One of the early ways for learning about the brain was to study people who have had brain damage. Researchers took note of what the patient could not do. Then by studying the absence of function, what was not there, they could infer by comparison the specific brain area associated with that function in the healthy brain. The best clinical evidence for how the brain influences function has been found when researchers could study patients who had suffered a known type of injury or gone through surgery on a specific part of the brain. They discovered that damage influences functioning in various ways, either specifically or globally. Chapter 4 covers one of the earliest documented cases, Phineas Gage. The dramatic transformation that Gage underwent from his injury became a pivotal example of how vitally important the frontal cortex is to personality. Another groundbreaking case was H. M. who underwent elective surgery to deal with his debilitating epilepsy. From the many years of study with H. M., neuroscientists gained strong evidence that memory functions are varied and some are localized to specific areas of the brain. An additional rich source of learning has come from the study of split-brain patients. The brain is divided into two hemispheres with many structures that seem to be repeated on both sides. Neuroscientists have studied patients who had damage to one side or the other, as well as those who had the connections between the two hemispheres, the corpus callosum, severed to help contain epilepsy. Some of the functions were found to be localized to one side or the other, but not both. This chapter explains the differences between the hemispheres. Also covered are patients with damage from brain injury, who suffer a specific loss such as temporal lobe damage, Capgras syndrome. Taken together, the cases covered in this chapter help to put the pieces of the puzzle together, to learn from what is and what is not, for a deeper understanding of the whole brain.