In 1848, 25-year-old railroad supervisor Phineas Gage was using a 3 foot 7 inch iron rod to pack blasting powder into a rock when he triggered an explosion that shot the rod straight through his left cheek and out of the top of his head. His survival and subsequent change in personality made him one of neuroscience's most famous case studies ? one of the first to highlight that specific areas of the brain affect particular aspects of behaviour.
Now, for the first time, researchers have reconstructed a model of the damage caused to the pathways that connected regions of Gage's brain. The result not only adds dimension to the historical case but also provides insights into conditions such as Alzheimer's disease that result in similar personality changes.
Due to the absence of Gage's original brain tissue and lack of a recorded autopsy, estimating the extent of brain damage has been difficult. In 2001, researchers at Harvard University were the last to be given permission by the Warren Anatomical Museum in Cambridge, Massachusetts, to scan Gage's skull. They used computed tomography ? essentially a 3D X-ray ? but the scans were lost after the researchers left the university. Through some "persistent cajoling" John Van Horn at the University of California, Los Angeles and colleagues recently unearthed the scans. "I just thought it's an absolute shame that this is one of the most valuable pieces of data in the history of neuroscience and it's lying in someone's desk drawer," says Van Horn.
He and his colleagues used the lost data to reconstruct a 3D image of Gage's skull. They then paired this with other facts about the incident (including the degree of bone breakage, dimensions of the iron rod, and the fact that he was reportedly speaking at the moment of injury, so is likely to have had his mouth open) to estimate the trajectory of the rod.
Damage assessment
They relied on other more subtle clues as well: "It appeared that the rod must have kissed the edge of a tooth to knock it loose," says Van Horn. After modelling 10 million potential trajectories, the team ultimately identified the most likely pathway that satisfied all of their constraints.
They then took two types of brain scans from 110 healthy men of the same age and handedness as Gage, and morphed the images to create a brain model that fitted into the cranial vault of Gage's skull. By combining this image with the rod's trajectory, they were able to model the expected degree of damage.
The regions of the brain most affected by the rod included the superior frontal sulcus, which is involved with self-awareness, and the insular cortex which controls emotion, among other things (PLoS One, DOI: 10.1371/journal.pone.0037454).
Their results suggest that after piercing his left cheek and continuing through the left side of his brain, the rod did not cross the midline of the brain, as has been previously suggested. However, by mapping the connections throughout his brain, Van Horn and his team discovered that the damage to the left side would have affected the right through the significant loss of white matter connections linking the damaged portions to the rest of the brain. Unsurprisingly, this would have left several regions on the right side of the brain heavily impaired, says Van Horn.
The work isn't only important to better understanding this historical case, but has present day implications as well, Van Horn says. "White matter damage in frontal lobes has been seen in dementia, and results in symptoms not dissimilar to Gage's, so it gives us a great insight into how damage in this area might affect behaviour."
If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.
Have your say
Only subscribers may leave comments on this article. Please log in.
Only personal subscribers may leave comments on this article
Subscribe now to comment.
All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.
If you are having a technical problem posting a comment, please contact technical support.
colton bo ryan the last waltz columbine earth day activities mel gibson splunk
কোন মন্তব্য নেই:
একটি মন্তব্য পোস্ট করুন