Phineas Gage and Cognitive Function
The brain is responsible for how humans think, learn, remember, see, hear, and speak. The decisions made based on these perceptions are responsible for a person’s behavior and emotional reactions. The decision making process is a complex brain function that takes place via interconnected neurons throughout the cerebral cortex. The brain makes predictions about the appropriate responses to stimuli based on learned experience from previous outcomes. The inability to predict the consequences of an action results in poor decision-making behavior insensitive to all outcomes. Railroad worker Phineas Gage survived extreme damage to the prefrontal cortex of his brain; after his recovery he continued life with the physical and most intellectual skills intact. The damage to Gage’s brain did cause major changes in his behavior, though.
Cerebral Cortex
“Perception, attention, emotion, planning and action, learning and memory, thinking, language and all other aspects of cognition all take place in the brain” (CNBC, 2009, para. 1). Cognitive function depends on the many subregions of the cerebral cortex, namely, the thalamus, amygdala, caudate and putamen, hippocampus, and cerebellum (Willmingham, 2007). Some of these structures, such as the caudate and putamen, are associated with more obscure cognitive functions, so the focus here will be on the amygdala, which is an important part in processing emotional information; and the hippocampus, which is involved in storing and retrieving memories. Advances in technology have allowed scientists an inside look at cognitive function in these areas of the brain. Magnetic resonance imaging (MRI) and positron emission tomography (PET) are imaging techniques that show brain activity quite clearly. Scientists use these images to compare normal and dysfunctional brains; and create computer simulations of functions in the brain after simulated damage, so that they can better understand the behavioral deficits a patient experiences after brain injury or damage (CNBC, 2009). Understanding how normal and dysfunctional brains operate cognitive function will help researchers develop new ways to treat patients with severe brain damage because of injury or other brain-deteriorating disorders. Perhaps the most famous case in cognitive psychology is that of Phineas Gage, a railroad worker who miraculously survived a freak accident. Gage’s story has left an enormous amount of information for neurologists and psychologists regarding cognitive function.
Phineas Gage
In 1848 while working on the railroads in Vermont, Phineas Gage detonated an accidental explosion that launched his tamping iron, a three-foot long solid steel bar, through his cheekbone and out through the top of his head; irreparably damaging the left side of his brain in the frontal area. The area of the brain believed to be damaged was Gage’s ventromedial prefrontal cortex (VMPFC) (Wagar & Thagard, 2004). Before his accident Gage worked as a foreman, and was considered to be efficient, well-balanced, and a successful businessman. Although Gage recovered physically enough to go back to work, he had become “…fitful, irreverent, and grossly profane, showing little deference for his fellow coworkers…” (Wagner & Thagard, 2004, p. 68). Contractors, who worked with Gage previously, were reluctant to rehire him after the accident, mostly because he was no longer efficient in making decisions regarding his own building plans, but also because of his unpredictable and irritable behavior. It is clear that the damage to Gage’s brain left him with a severe cognitive deficit, unable to control his inhibitions and emotional reactions. Simon Gerhand states that damage to the posterior regions of the brain produce obvious dysfunction of cognitive ability, whereas damage to the frontal region usually does not affect intellectual function so much as it changes a person’s behavior, as was the case with Phineas Gage (1999). Anyone who ever met Phineas Gage after his accident would probably never know there was anything wrong with him; accept maybe that he was kind of a jerk, which are qualities that many people embody without damage to their brains. To the people that knew Gage, though, he was a completely different person after the accident, which left a strain on his professional and personal relationships.
Dysfunction of the Cortex
Damage to the prefrontal cortex can have negative effects on cognitive abilities such as planning, reasoning, and problem-solving. Prefrontal dysfunction is also prevalent in affective disorders such as schizophrenia, whereas ventromedial lesions show a dysfunction in the ability to “…experience appropriate emotional responses…,” which can impair decision-making (Gerhand, 1999, para. 2). Neuronal activity in the cortex is fueled by the experiences humans gain through the environment; the information is taken in, delivered, and processed by the interconnected neurons (CNBC, 2009). Somatic markers in the VMPFC convert emotional signals that influence decision-making by outlining positive and negative actions, and highlighting the options with the predicted highest positive outcomes. The predictions are based on memories of previous outcomes, which influence the prevalence of a positive or negative prediction. In a normal brain the amygdala, in association with the VMPFC, helps form memory traces, which enable a person to predict the outcome of an emotional response (Wagar & Thagard, 2004). The data produced by the correspondence between the VMPFC and the amygdala is forwarded to the nucleus accumbens (NAcc) where it is analyzed to be a correct response, and sent to the motor areas of the cortex to produce an emotional reaction (Wagar & Thagard, 2004). The NAcc acts as a gateway unlocked by the hippocampus, and which allows access to the VMPFC and the amygdala during the processing of somatic markers.
Conclusion
People like Phineas Gage that have experienced damage to the VMPFC lose the ability of communication through the NAcc gateway, which inhibits the process of somatic markers; thus retarding the ability “…to integrate cognitive and emotional information to discern the future consequences…” of one’s actions (Wagar & Thagard, 2004, p. 67). With the help of technology, scientists can explore the effects of damage to the frontal cortex on behavior, reasoning, and decision-making abilities. Dysfunctional behavior prompts the study of the origins of the behavior, and understanding why humans behave in certain ways can produce solutions to dysfunctional behavior. Understanding the origins of cognitive functions enables researchers to specify the areas of the brain responsible for different functions, which provides an avenue for the research of treatments to rectify cognitive dysfunction.
References
Gerhand, S. (1999). Book review: The prefrontal cortex—executive and cognitive functions.
Brain: A Journal of Neurology, 122(5), pp. 994-995. Oxford University Press. Retrieved
From http://brain.oxfordjournals.org/cgi/content/full/122/5/994
The Center for the Neural Basis of Cognition (CNBC): Integrating the Sciences of Mind and
Brain. (2009). Research in the CNBC. Retrieved from http://www.cnbc.cmu.edu.research
Wagar, B. M., & Thagard, P. (2004). Spiking phineas gage: A neurocomputational theory of
Cognitive-affective integration in decision making. Psychological Review, 111(1).
Retrieved from http://cogsci.uwaterloo.ca/Articles/spiking.pdf
Willmingham, D. T. (2007). Cognition: The thinking animal (3rd ed.). Upper Saddle River, NJ:
Pearson/Allyn & Bacon.
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