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The social brain: new clues from old skull.

Phineas Gage died in 1861, about a dozen years after surviving a horrifying accident in which an iron rod hurtled through his face, skull, and brain. More than 130 years later, brain imaging techniques have provided a new look at Gage's wounds that adds to emerging evidence on how the brain's frontal lobes facilitate social decision making and a sense of responsibility toward others.

"The damage involved left and right prefrontal [areas] in a pattern that, as confirmed in Gage's modern [brain-damaged] counterparts, causes a defect in rational decision making and the processing of emotion," argue Hanna Damasio, a neurologist at the University of Iowa Hospitals & Clinics in Iowa City, and her colleagues. The 25-year-old Gage envisioned no such contributions to science in 1848 as he directed the controlled blasting of uneven terrain in Vermont prior to the laying of new railroad tracks. He mistakenly triggered one explosion before an assistant had covered the strategically placed explosive powder with a buffer of sand; the force of the blast threw a 3-1/2-foot-long tamping iron through his head.

Remarkably, Gage regained consciousness almost immediately and walked away from the site with the help of his work crew. Although he remained as able-bodied and intelligent as before the accident, his personality changed irrevocably. Formerly a top-flight worker and popular with peers, Gage began to behave in irresponsible ways. He refused to honor commitments on the job and with friends. He offended others with his sudden tendency to sprinkle profanities throughout his conversation and to otherwise depart from social conventions of the time.

Gage lost his job soon after the accident and spent years wandering. He died in the custody of his parents.

The physician who treated Gage in the months after his injury, John Harlow, learned of his former patient's death and convinced Gage's family to have his body exhumed in 1866 so his skull could be removed and kept as a record of this unusual medical case. The skull and the offending tamping iron, which had been buried with Gage, have since resided in a Harvard University museum.

Harlow wrote a paper in 1868 arguing that Gage suffered localized damage to the frontal lobe, an indication that the brain contained structures responsible for "rational" personal and social behavior. But the exact position of Gage's injury could not be determined from his skull alone, and researchers generally dismissed Harlow's theory.

Enter modern technology. Damasio's group created a three-dimensional computerized skull from X rays and measurements of Gage's skull. Their digital version included the tamping iron's entry and exit holes. They then simulated possible trajectories of the projectile through a reconstruction of a human brain that closely matched Gage's estimated brain dimensions.

The rod's most likely path ran diagonally through the middle of the frontal lobes, missing structures involved in language production and muscle control, the scientists report in the May 20 SCIENCE. Gage's injury closely resembles brain damage documented for 12 patients at the University of Iowa, they contend. Like Gage, these individuals display pervasive irresponsible behaviors, as well as difficulty in expressing and interpreting emotions.

Brain circuits that mediate emotion may participate in various types of social decision making, Damasio and her coworkers theorize. This collaborative effort may depend on the cerebral terrain Phineas Gage unintentionally blasted away, they assert.
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Title Annotation:digital versions of Phineas Gage's skull suggests that iron rod wounded areas of frontal lobe responsible for personal and social behavior
Author:Bower, Bruce
Publication:Science News
Article Type:Brief Article
Date:May 21, 1994
Words:549
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