An important neural pathway in the brain first described in the late nineteenth century but then inexplicably ignored in the scientific literature has been "rediscovered," neuroscientists say.
A researcher looking at scans of human brains noticed a large, fibrous pathway that appeared to form a portion of the network of connections we use in processing visual information, but he discovered he couldn't find a mention of it in any of modern-day textbooks on anatomy.
"It was this massive bundle of fibers, visible in every brain I examined," said Jason Yeatman, a Stanford University graduate student at the time and now at the Institute for Learning & Brain Sciences of the University of Washington. "It seemed unlikely that I was the first to have noticed this structure; however, as far as I could tell, it was absent from the literature and from all major neuroanatomy textbooks."
The bundle was first described in the 1880s by German neurologist Carl Wernicke who named it the "vertical occipital fasciculus."
However, its vertical orientation contradicted the assertion of one of the era's most renowned neuroanatomists, Theodor Meynert, who declared brain connections could only travel horizontally between the front and the back of the brain, not up and down.
Other neurologists, who supported his conclusion that the brain's white matter tracts are oriented horizontally in each hemisphere, disputed Wernicke's description of a vertical bundle, and although it appeared in other textbooks including the 1918 edition of Gray's Anatomy, Wernicke's discovery soon disappeared into obscurity and was absent from the scientific literature.
Yeatman and colleagues at Stanford University went delving into the history and the controversy surrounding the brain structure, a search they detailed in a study published in the Proceedings of the National Academy of Sciences.
Reading the yellowing pages of a 19th century atlas of the brain in the Stanford Medical Library's basement provided Yeatman and postdoctoral researcher Ken Weiner with an "aha!" moment.
"Kevin found an atlas, written by Carl Wernicke near the turn of the (20th) century, that depicted the vertical occipital fasciculus," Yeatman said. "The last time that atlas had been checked out was 1912, meaning we were the first to view these images in the last century."
The rediscovery is not just a matter of correcting a scientific oversight, Yeatman says; the vertical occipital fasciculus begins in the occipital lobe at the back of the head, and thus is a significant part of the brain's visual processing system.
"We believe that signals carried by the VOF play a role in many perceptual processes, from recognizing a friend's face to rapidly reading a page of text," said Yeatman.
He has begun a study of how learning to read impacts brains structure and says he "wouldn't be surprised if the VOF ends up playing a central role in that investigation."