It's easy enough to understand the ghastly accident that befell poor Phineas Gage in Cavendish, Vermont on Sept. 13, 1848: the 25-year-old railroad worker was using an iron rod to tamp down blasting powder when the stuff exploded, sending the 43-inch-long, 13-pound rod through his left cheek and out the top of his head.
What's not so easy to understand is why Gage survived the accident--or the precise reason for the dramatic change in his personality afterward. John Harlow, the doctor who treated the once-affable Gage, wrote that he "could not stick to plans, uttered 'the grossest profanity' and showed 'little deference for his fellows,'" Smithsonian magazine reported in 2010.
But now researchers are closing in on answers.
For a new study published in the May 16 issue of the journal PLoS One, scientists at UCLA used brain-mapping data from computed tomography (CT) and magnetic resonance imaging (MRI) scans to determine the specific damage inflicted on the neurological "pathways" in Gage's brain.
"What we found was a significant loss of white matter connecting the left frontal regions and the rest of the brain," study co-author Jack Van Horn, an assistant professor of neurology at the university, said in a written statement. "We suggest that the disruption of the brain's 'network' considerably compromised it. This may have had an even greater impact on Mr. Gage than the damage to the cortex alone in terms of his purported personality change."
Only about 4 percent of Gage's cerebral cortex was directly affected by the rod, the study showed. But more than 10 percent of the white matter was damaged. The white matter is the fatty tissue within the brain that coordinates communication between its different regions.
In addition to helping explain Gage's deterioration, the study showcases the power of brain mapping--a technology that neurologists believe will lead eventually to an understanding of the links between the brain's "wiring" and specific mental disorders, according to the statement.
"The extensive loss of white matter connectivity, affecting both hemispheres, plus the direct damage by the rod, which was limited to the left cerebral hemisphere, is not unlike modern patients who have suffered a traumatic brain injury," Van Horn said in the statement, adding that the loss of connectivity was analogous to that seen in Alzheimer's disease and other neurodegenerative diseases.
What happened to Gage after the accident? He worked at a stable in New Hampshire and then as a stagecoach driver in Chile before moving to San Francisco. He died there after a series of seizures 12 years after the accident.
But not all of Gage is gone. His 189-year-old skull is on display at Warren Anatomical Museum in Boston. The tamping rod? It's there too.