Phineas Gage Paper At the age of 25 Phineas Gage was a bright, promising foreman working for the Rutland and Burlington railroad in Cavendish, Vermont. As was the practice of the times, tamping powder was used to blast drill holes for the preparation of laying track (Wickens, 2005). Gage was using a tamping rod to compact the powder in the holes before detonation when suddenly a precipitous explosion propelled the rod, which was 1.1 meters long, 6 millimeters thick, and weighing 6 kilograms, through his left cheek and brain, exiting out the vault of his skull (Leach & O'Driscoll, 1998). Surprisingly, Gage remained conscious on the ride to the doctor. Once there, Dr. Harlow, the attending physician, bandaged his wounds, which bled for an additional 2 days. Gage showed no obvious, immediate mental deficits, but an aggressive viral infection set in at the damaged area which led to a month of semiconscious recovery. The infection finally abated and Gage made a complete recovery, except for blindness in his left eye and weakness in the left side of his face. However, upon returning to work it became quite clear that Mr. Gage was not entirely himself. The damage to Gage’s brain was localized in the ventromedial prefrontal cortex; nevertheless, in order to understand the personality changes that Gage underwent after his recovery it is necessary to first examine the underlying neurological and cognitive interplay thereof. Cognition and Neurology of Consequence Prediction The somatic-marker hypothesis, first proposed by A. Damasio, stipulates that somatic markers, the feelings and emotional reactions that we associate with certain responses, play an integral part in the prediction of long-term outcomes (Thagard & Wagar, 2004). Somatic markers act as a mediating force in the cognitive representation of decision-making by highlighting outcomes that have positive predictions and negating outcomes that have negative predictions. It is through this process that an organism is able to integrate affective and memory information to properly predict the future outcome of current events. Implicated in the formation and integration of somatic markers into the mechanism of decision making is the ventromedial prefrontal cortex (VMPFC), the hippocampus, the amygdala, and the nucleus accumbens (NAcc). The VMPFC works in tandem with the amygdala to form the memory traces necessary to relate memory to affective information. It is the NAcc that acts as the contextual gateway, only allowing situation-relevant memory traces to pass into higher level cognitive processes, as mediated by hippocampal input. It is through the integration of situation relevant memory traces by the VMPFC and the amygdala, as arbitrated by the contextual gateway of the NAcc, which is in turn controlled by input from the amygdala, that gives rise to the assimilation of somatic markers into the cognitive mechanism of decision making. The Case of Phineas Gage The lesion to Gage’s brain was highly localized, only damaging the VMPFC. After his accident Gage was described as, “…being exceedingly capricious and childish, but with a will as indomitable as ever; is particularly obstinate; will not yield to restraint when it conflicts with his desires” (Leach & O'Driscoll, 1998, p. 1673). In fact, Gage’s supervisor recounted

…[he] considered the change in [Gage’s] mind so marked that they could not give him his place again… He is fitful, irreverent, indulging at times in the grossest profanity (which was not previously his custom), manifesting but little deference for his fellows… (Leach & O’Driscoll, 1998, p.

Because Gage’s VMPFC was lesioned he was not longer able to properly incorporate memory traces into the somatic markers that eventually affected upper-level cognition. He was not able to see the future consequences of his actions because he was not able to use affective information in conjunction with memory information to inform the decision to , say, abstain from profanity. Conclusion The story of Phineas Gage, however tragic, brought to light many questions of the mind-body interaction and the localization of the brain. At the time we did not possess functional magnetic resonance scans (fMRI) or computerized axial tomography scans (CAT). It was decades later before the scientific community was able to explain the specific way in which the damage to Gage’s VMPFC affected his ability to properly retrieve memory traces for the integration and assimilation of somatic markers for the use of upper-level cognitive decision making. References Leach, J. P., & O'Driscoll, K. (1998). `No longer Gage': An iron bar through the head. British Medical Journal, 317(7174), 1673. Retrieved July 21, 2009, from EBSCOHost Database. Thagard, P., & Wagar, B. M., (2004). Spiking Phineas Gage: A neurocomputational theory of cognitive-affective integration in decision making. Psychological Review, 111(1), 67-79.Retrieved July 21, 2009, from EBSCOHost Database. Wickens, A. (2005). Foundations of biopsychology, 2e. Upper Saddle River, N.J.: Pearson Hall.