Using brain-imaging data that had been lost to science for a decade, researchers studied the damage that was done to the white matter ‘pathways’ connecting the different regions of the brain.
In 1848, Phineas Gage worked as a supervisor at a railroad. While packing explosives into a hole, he caused an explosion that drove the packing rod through his skull. The packing rod was later found covered in his blood and brain matter.
He’s famous not only for surviving, but for the large changes that occurred in his personality afterwords. The injury had caused extensive damage to most of his left frontal lobe, and whereas he was described as affable and friendly before the injury, afterwords he was said to be irreverent and profane.
The research found that while only 4 percent of the cerebral cortex was intersected, 10 percent of his total white matter was damaged, which likely contributed to the changes in his personality.
White matter is the connector for the billions of neurons that create memory and ‘reason’. The research was done to gain a better understanding of similar brain disorders, such as Alzheimer’s, different forms of dementia, and traumatic brain injuries.
“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.”
LONI is in a joint effort with the National Institutes of Health and Massachusetts General Hospital to map the trillions of links between the brain’s 100 billion or so neurons, the ‘connectome’. Doing so should allow a better understanding of the causes of degenerative brain diseases. So, it was considered useful to take a look a second look at the damage to Phineas Gage’s brain.
The researchers used imaging data that had been taken in 2001, and then lost for 10 years. They recovered the data, which was the highest resolution modeling data available for Gage’s skull. And after determining the exact trajectory of the packing rod, they used modern brain images of males that were Gage’s age and handedness to assess the damage done.
They found that almost 11 percent of his white matter was damaged, and 4 percent of his 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.”
“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.”
Source and Images: UCLA