A major brain pathway first described in an 1881 neuroanatomy atlas — and then completely forgotten — has been rediscovered and confirmed by scientists using modern scanning techniques.
Above: A drawing by German-Austrian neuroanatomist Theodor Meynert that appeared in an 1892 article depicts other prominent brain pathways but leaves out the vertical occipital fasciculus. Caption and image: UW Today/Jason Yeatman
It's called the vertical occipital fasciculus — a large, fiber pathway that carries critical signals required for many perceptual processes, such as recognizing a friend's face and rapidly reading a page of text.
Yeah — a pretty major brain part. So how could such a thing go "missing" in the scientific literature for over 130 years? The answer has to do with a scientific disagreement and haphazard naming methods.
The first images of the vertical occipital fasciculus, with varying names and abbreviations. Seeing Wernicke's 1881 drawing from a monkey brain was the "aha" moment that helped the researchers piece the story together. The drawings by Obersteiner and Sachs are from human brains. Caption and image: UW Today/Jason Yeatman
Back in 1874, the renowned anatomist Carl Wernicke wrote about a fiber pathway in a monkey brain he was examining. He called it "senkrechte Occiptalbündel" (translated as vertical occipital bundle). Trouble is, the described vertical orientation went against the thinking of one of the most famous neuroanatomists of the era, Theodor Meynert, who insisted that brain connections could only travel in between the front and the back of the brain, not up and down.
This series of images shows drawings of brain connections that the researchers found in the various atlases they studied. Heinrich Obersteiner's 1888 schematic, Sir Edward Schaefer's 1893 woodblock carving, and Gray's 1918 illustration all show the vertical occipital fasciculus. But Ludwig Edinger's 1885 drawing leaves out the fiber pathway. Caption and image: UW Today/Jason Yeatman
What's more, scientists from this era lacked a shared process for naming the brain structures they found. The historical literature describes such things as "Wernicke's perpendicular fasciculus," "perpendicular occipital fasciculus of Wernicke," and "stratum profundum convexitatis." Eventually, the damn thing just disappeared from neuroanatomy texts, and thus forgotten.
A camera lucida drawing made by E.J Curran depicts a postmortem dissection of the vertical occipital fasciculus. Curran described the VOF as "striking in its appearance, size, and complete isolation from the longitudinal fibers under it." Image and caption UW Today/Jason Yeatman
Recent work by Jason Yeatman, Kevin Weiner, and colleagues has now corrected this oversight. They discovered the massive bundle of fibres back in 2012, but were shocked to discover that it wasn't mentioned in any of the modern-day anatomy books. The team eventually traced it back to the 1881 discovery.
As noted in a University of Washington release:
The researchers used a type of MRI measure called diffusion-weighted imaging to measure the size of the pathway and see where in the brain it went. Across brain scans taken from 37 subjects, they found that the vertical occipital fasciculus begins in the occipital lobe — the part of the brain's visual processing system located at the back of the head.
The researchers also created an algorithm to help researchers study the pathway, which will hopefully lead to a better understanding of its role in human cognition and in patients.