Localization of Brain Function

Psychologists have found that the brain often shows “localization of function”. This means that different parts of the brain carry out different tasks, for example, vision, voluntary movement and speech. The idea is that not all parts of the brain do the same thing, and that each part functions on its own, without the aid of other areas of the brain. This may seem obvious, but other organs, such as the liver, do not show localization of function; one part of the liver does the same thing as a part on the opposite side. A famous example of brain localization is the case of Phineas Gage; a railway worker in 1848, who one day, while trying to blow out a hole in the side of a mountain, had a metal rod shoot through his cheek, into his brain, and out the top of his head, landing over 100 meters away. The pole took with it a substantial amount of Gage’s brain, but surprisingly enough he was awake and mobile throughout the experience, even able to sit up and ride to the nearest hospital and wait for a doctor to examine him.

After his examination, Dr Harlow came to the conclusion that Gage was fine. This shocked many people, as brain localization had not yet been studied, and at the time the idea of a man loosing part of his brain and still being able to function was outrageous. It was only a few weeks later that Phineas’s friends and family began to notice significant changes in his personality and his moods; he had become inappropriate, rude, impulsive and irritable. The longitudinal study of his brain showed damage to his frontal lobe, an area of the brain that is now known to affect personality and social behavior. This case study opened up the floor for other psychologists to further study the idea of brain localization. This change in personality and mood never reversed to its normal state, which shows that another area of the brain did not take over the role of the damaged frontal lobe in balancing Gage’s personality and mood regulations. Another example of localization of brain function is that of a 60 year old Italian man, AD. AD suffered cardiac arrest, which damaged his frontal and temporal lobes. The damage done caused him to alter his personality when in the company of different people; gaining the patient the nick-name “The Human Chameleon.”

When AD was in the company of lawyers, he would invent a detailed background story to support his claim of being a lawyer. When in the company of a doctor, he would do the same but claim to be a doctor. The interesting twist on his case is that AD had anosognosia; a lack of insight into his odd behavior. This meant that AD truly believed his own lavish stories. His condition is a form of anterograde amnesia, which caused him to forget everything prior to the cardiac arrest, thus allowing him to invent past lives. The case of AD shows that the area that was damaged (the frontal and temporal lobes)’s function was not taken over by another area of the brain, as AD never regained the memories lost in the accident.

However, psychologists have also found a counter-argument for localization of brain function; and that is brain plasticity. Brain plasticity is the idea that if one part of the brain stops functioning, another part will take over that role. The idea of brain plasticity has been around for hundreds of years. The ancient Greeks accepted the idea, believing that one could train their mind, just like training a body. Around the time of Galileo, the idea was dismissed, as scientists began to see the world mechanically, with each object/organ being well-defined with unchanging roles. It was these ideas that led to the idea of our brains being “hardwired”, an idea that today is being slowly disregarded.

An example of brain plasticity is the case of Cheryl Schiltz, a 39 year old woman who in 1997 developed an infection in her inner ear canal after a routine operation. The infection caused her to be prescribed gentamicin, an antibiotic that when over used, can cause damage to the cells in the inner ear. In Cheryl’s case, gentamicin destroyed her vestibulary system (the inner ear canals that allow us to tell up from down). Tests showed she had only 2% of her vestibulary function left, and as a result had severe issues with her balance. Her doctor found an bizarre way to treat her. He fitted her with a helmet fitted with motion sensors.

These gave signals to a metal strip that was placed in her mouth. Now, as she tipped forward, she felt a tingle ripple to the tip of her tongue. As her head moved to the side, the tingle rolled sideways. After time, her brain learnt to turn the tingles into a sense of balance. Eventually she needed the helmet less and less. Her doctor, Dr Norman Doidge, came to the conclusion that her brain learned from the tiny signals left in her inner ear, and “recruited” other brain cells to help Cheryl balance. This case shows that the brain is capable of learning and adapting to certain injuries. In conclusion, psychologists have found evidence to support the idea of Brain Localization; the idea of different areas of the brain having individual roles to perform, as well as evidence that may help prove the idea of Brain Plasticity; where other areas of the brain can stand in for damaged regions and help perform their tasks.

References:

http://pd.scisdragons.net/ibpsych/2011/09/04/localization-of-brain-function-4/ http://viper.eng.iastate.edu/ncseminar/presentations/week5.pdf http://www.guardian.co.uk/science/2009/apr/07/brain-neuroscience-stroke-depression