Centuries of philosophy and science have been dedicated to unraveling the mystery behind how cognition occurs, how it maps to areas of the brain, and to what degree cognition is dependent upon these various areas in which cognitive activities are located. Modern neuroscience has helped tremendously to provide some answers as have tests on brain trauma patients such as Phineas Gage which revealed startling changes in individual behavior that can be linked to damage in specific locations of the brain. Even though studies continue to discover new information, there is strong evidence to support the premise that specific brain locations are dedicated to certain cognitive functions.dedicated to certain cognitive functions.
Phineas Gage was an upstanding citizen that lived Cavendish, Vermont in the mid-1800s. Phineas worked as a railroad crew foreman and was considered by his employer to be a highly reliable, responsible man with morals, and a true model citizen. However, an accident that occurred in 1848 drove an iron pole called a tamping iron, through Phineas left cheek and out the top of his skull. According to reports, Phineas was able to get help from a physician, John Martyn Harlow, with whom Phineas carried on a discussion even during the initial treatments. John Martyn Harlow continued to treat Phineas for months after the accident and recorded the substantial changes in Phineas behavior that occurred during that time. It was a significant discovery in modern medicine and some even argue, the beginning of cognitive neuroscience as we know it today. Phineas did not lose motor movement capability, speech ability or apparent cognition abilities. However, Phineas did become a “different person.” Phineas was no longer the model citizen, having little regard for others, known for profane speech, unreliable, and no longer able or willing to follow plans and schedules. In fact, the railroad crew where Phineas was working and which had referred to Phineas as a “model citizen” refused to take him back after he had recovered from the accident because of his drastic, negative change in personality. According to people that knew Phineas prior to the accident, Phineas was Phineas no longer.
In 1861 Paul Broca made another startling discovery regarding a man named “Tan” during a post mortem investigation. Tan was able to understand language spoken to him, and had full motor function of all areas of his mouth required for speech, but was unable to speak the same language (or any language for that matter). Essentially, Tan could communicate with others using spoken language but only in one direction. Tan could receive communication but not speak the same. Paul Broca discovered during the post-mortem investigation that Tan had damage to a specific brain location located in the left frontal cortex (now known as Broca's Area). This discovery again, like the case of Phineas Gage, reinforced the idea that there are locations in the brain dedicated to specific forms of cognition and activities. Broca's Area was defined by Paul Broca as a “speech centre” and became the first location in the brain identified with a specific function.
In 1871 neurologist Carl Wernicke discovered another brain location responsible for handling specific aspects of speech. Located in the posterior portion of the brain's left temporal lobe, this area processes speech and words that are both spoken and received. Wernicke found that patients with a lesion (damage spot) in that specific brain location were able to speak and receive spoken language however their speech was unintelligible and they also had a hard time understanding what others were communicating to them. This brain location, now known as Wernicke's Area, was later found to be directly connected to Broca's area by a series of nerve fibers that are now referred to as arcuate fasciculus.
The discoveries noted by Paul Broca and Carl Wernicke, and the case study of Phineas Gage, as a whole, reveal that the brain indeed does have areas that are dedicated to specific functions. Since the time of these discoveries, maps of brain locations that define functions handled by specific areas have been drafted based upon a combination of scientific experimentation and the study of patients with damage in specific areas of the brain, also known as lesions. Other experimentation involved testing specific brain locations during surgery in an attempt to alleviate the symptoms of patients with neurological disorders such as epilepsy. Using this method, Dr. Wilder Penfield was able to map the functions of the Primary Motor Cortex area consisting of the pre-motor area or PMA and the supplementary area or SMA to determine which areas can be removed and which areas should not be removed when working to decrease epileptic symptoms. It was also found that areas dedicated to a specific function may not be the only areas involved in that function. For example, in the case of voluntary motor activities, the prefrontal cortex and posterior parietal cortex also play a role in voluntary motor activities.
Areas of the brain that handle cognitive functions have also been identified following the methods used by Wernicke (lesion method) and Dr. Wilder Penfield (through direct stimulation). For example, there is a distinct difference between the functions of the right and left hemispheres of the brain. It has been found and is now generally accepted that the left hemisphere of the brain handles logical functions with detail orientation, such as math and problem solving whereas the right hemisphere handles emotions, imagination, and is less detail oriented and more focused on holistic viewpoints
Research continues to move forward, gaining insight into the particulars of how our brain is mapped using more advanced methodologies such as infrared spectroscopes so that non-invasive experimentation can be performed on subjects enabling scientists to have a more in-depth understanding of how cognition and brain locations are linked together.