The study of brain injury is an imperative tool when trying to understand the in-depth workings of “the most complex object in the known universe”. We have been studying the brain for thousands of years. From Hippocrates in 468BC, describing epilepsy as a disturbance of the brain, to our modern day MRI and CT scans able to image the brain in great detail our knowledge is always growing. However the study of Brain Injury has given us the most advances throughout this journey of discovery.
The study of brain injury has given us great insight into the functionality of different regions allowing us to locate the areas of the brain affected by neurological disorders and other diseases and thus develop new strategies to treat brain disorders. There are two main types of brain injury. Traumatic Brain Injury (TBI) is caused by an external force such as a blow to the head that causes the brain to move inside the skull resulting in damage. An Acquired Brain Injury (ABI) occurs at the cellular level.
These include degenerative diseases such as parkinsons, brain development problems such as autism, blood flow issues including stroke and infection by bacteria and viruses. One of the pioneers of brain injury research was Pierre Paul Broca who reported inferior frontal gyrus impairments lead to a loss of ability to produce language after injury to this area. Since then, the approximate region he identified has become known as Broca’s area, and the deficit in language production as Broca’s aphasia.
Another prominent name in this field was Roger W. Sperry who won a Nobel prize in 1981 for his discoveries concerning the functional specialization of the cerebral hemispheres. The brain is divided into two hemispheres, the left and right, connected in the middle by a bridge known as the corpus callosum. People who suffered from epilepsy would sometimes have their corpus collosum severed thus seprating the two sides of the brain relieving the effects of epilepsy, a disease that causes intense and persistent seizures.
Sperry wanted to see if this severed corpus collusom had any effect on the patient’s language, vision, and motor skills. He conducted a series of experiments changed our view of the brain forever. He was able to define the the sides of the brain responsible for different functions and also how those function interlink. Another pioneer of brain injury was Carl Wernicke, a German neurologist and psychiatrist who, in 1874, hypothesized a link between the left posterior section of the superior temporal gyrus and the interpreatation of written and spoken language.
He did this on the basis of the location of brain injuries that caused aphasia. In this condition there is a major impairment of language comprehension and sentence or word construction. Probably one of the most famous cases of brain region functionality as a result of brain injury comes from the case of Phineas Gage. Phineas Gage was a railway engineer who had a large metal pole driven through his head damaging most of his left frontal lobe. John Martyn Harlow, the doctor who treated him for a few months afterward studied the mental chages that occured afterward.
The doctor found that his friends refered to him as “no longer Gage,” as in personality had changed dramatically. Harlow wrote the balance between his “intellectual faculties and animal propensities” seemed gone. He could not stick to plans, uttered “the grossest profanity” and showed “little deference for his fellows”. From this evidence it was learned that that region of the brain was associated with planning, temperment and also personality.
Another example would be Henry Molasion a patient who underwent a bilateral medial temporal lobectomy to surgically remove the anterior two thirds of his hippocampi and other memory related regions. He was widely studied from late 1957 until his death. HM was unable to form new long-term memories of new events. Since HM did not show any memory impairment before the surgery, the removal of the medial temporal lobes can be held responsible for his memory disorder.
Consequently, the medial temporal lobes can be assumed to be a major component involved in the formation of semantic and episodic long-term memories . Further evidence for this assumption has been gained by studies of other patients with lesions of their medial temporal lobe structures. His case played a very important role in the development of theories that explain the link between brain function and memory. Overall the study of Brain injury has had a massive contribution on our functional knowledge of the brain.