May 18, 2012
Probing Phineas Gage's Connectome
|Anyone familiar with psychology or neuroscience will be familiar with the incredible case of Phineas Gage, the railroad worker who had a metre-long iron rod propelled straight through his head at high speed in an explosion. Gage famously survived this horrific accident, but underwent dramatic personality changes afterwards. Now, neuroscientists from the University of California, Los Angeles have produced Gage's connectome - a detailed wiring diagram of his brain, showing how its long-range connections were altered by the injury.|
A similar recent case is that of Dante Autullo, who impaled his brain with a nail gun, and has experienced only minor damage.
Like Autullo, Gage lived, becoming the most famous case in the history of neuroscience because of the injury’s reported effects on his personality and behavior, which were said to be profound.
Gage went from being an affable 25-year-old to one that was fitful, irreverent and profane. His friends and acquaintances said he was “no longer Gage.”
Over the years, various scientists have studied and argued about the exact location and degree of damage to Gage’s cerebral cortex and the impact it had on his personality. Now, for the first time, researchers at UCLA, using brain-imaging data that was lost to science for a decade, have broadened the examination of Gage to look at the damage to the white matter “pathways” that connect various regions of the brain.
Reporting in the May 16 issue of the journal PLoS ONE, Jack Van Horn, a UCLA assistant professor of neurology, and colleagues note that while approximately 4 percent of the cerebral cortex was intersected by the rod’s passage, more than 10 percent of Gage’s total white matter was damaged. The passage of the tamping iron caused widespread damage to the white matter connections throughout Gage’s brain, which likely was a major contributor to the behavioral changes he experienced.
|Gage with the rod that impaled his skull and brain.|
“What we found was a significant loss of white matter connecting the left frontal regions and the rest of the brain,” said Van Horn, who is a member of UCLA’s Laboratory of Neuro Imaging (LONI). “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.”
Since Gage’s 189-year-old skull, which is on display in the Warren Anatomical Museum at Harvard Medical School, is now fragile and unlikely to again be subjected to medical imaging, the researchers had to track down the last known imaging data, from 2001, which had been lost due to various circumstances at Brigham and Women’s Hospital, a teaching affiliate of Harvard, for some 10 years.
The authors were able to recover the computed tomographic data files and managed to reconstruct the scans, which revealed the highest-quality resolution available for modeling Gage’s skull. Next, they utilized advanced computational methods to model and determine the exact trajectory of the tamping iron that shot through his skull.
Finally, because the original brain tissue was, of course, long gone, the researchers used modern-day brain images of males that matched Gage’s age and (right) handedness, then used software to position a composite of these 110 images into Gage’s virtual skull, the assumption being that Gage’s anatomy would have been similar.
Van Horn found that nearly 11 percent of Gage’s white matter was damaged, along with 4 percent of the cortex.
“Our work illustrates that while cortical damage was restricted to the left frontal lobe, the passage of the tamping iron resulted in the widespread interruption of white matter connectivity throughout his brain, so it likely was a major contributor to the behavioral changes he experienced,” Van Horn said.
“Connections were lost between the left frontal, left temporal and right frontal cortices and the left limbic structures of the brain, which likely had considerable impact on his executive as well as his emotional functions.”
And while Gage’s personality changed, he eventually was able to travel and find employment as a stagecoach driver for several years in South America. Ultimately, he died in San Francisco, 12 years after the accident.
“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,” he said.
“And it is analogous to certain forms of degenerative diseases, such as Alzheimer’s disease or frontal temporal dementia, in which neural pathways in the frontal lobes are degraded, which is known to result in profound behavioral changes.”
Van Horn noted that the quantification of the changes to Gage’s brain’s pathways might well provide important insights for clinical assessment and outcome-monitoring in modern-day brain trauma patients.
SOURCE The Guardian
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Tags: brain injury, connectome, health, Jack Van Horn, LONI, medicine, neuroscience, Phineas Gage, UCLA
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