A new old discovery

Some say that science has been looking at the brain for some time now and yet there is no agreed explanation of how it works. This is sometimes followed by – and therefore maybe science will never understand the brain. But the brain is much more complex than most people think and the tools to examine it are far less powerful as well. On a regular basis new aspects of the brain are discovered, not little details but major discoveries.

Recently there was a large white matter tract found. Really it was re-found because it had been previously reported, doubted, and forgotten. It had been found in the 1880s. This is basic brain anatomy in the most closely studied part of the cortex, the visual cortex, and it illustrates just how little is known about the brain. It would be like a major artery was missing from the knowledge of the circulatory system.

ScienceDaily has an item on this (here). The announcement is in the paper: Jason D. Yeatman et al. The vertical occipital fasciculus: A century of controversy resolved by in vivo measurements. PNAS, November 2014 DOI: 10.1073/pnas.1418503111.

Carl Wernicke discovered it; Yeatman and Weiner re-discovered it. They call it the vertical occipital fasciculua (VOF). There are three ways in which the knowledge could have been forgotten.

A sc ientific disagreement — In an 1881 neuroanatomy atlas, Wernicke, a well-know n anatomist who in 1874 discovered “Wernicke’s area,” which is essential for language, wrote about a fiber pathway in a monkey brain he was examining. He called it “senkrechte Occiptalbündel” (translated as vertical occipital bundle). But its vertical orientation contradicted the belief of one of the most renowned neuroanatomists of the era, Theodor Meynert, who asserted that brain connections could only travel in between the front and the back of the brain, not up and down. Haphazard naming methods — The 1880s and 1890s were a fertile time in the neuroanatomy world, but scientists lacked a shared process for naming the brain structures they found. Looking at drawings of the brain from this time period, Yeatman and coauthors saw that the fiber pathway that they were looking for appeared in brain atlases but was called different things, including “Wernicke’s perpendicular fasciculus,” “perpendicular occipital fasciculus of Wernicke,” and “stratum profundum convexitatis.” “When we started, it was just for our own knowledge and curiosity,” said Weiner, who’s also the director of public information at the Institute for Applied Neuroscience, a nonprofit based in Palo Alto, California. “But, after a while, we realized that there was an important story to tell that contained a series of missing links that have been buried for so long within this puzzle of historical conversation among many who are considered the founders of the entire neuroscience field.” Also the way dissections were done changed so that the VOF was less visible.

There are more details in Mo Castandi’s blog (here)

The new measurements delineate the full extent of the VOF, revealing it as a flat sheet of white matter tracts that extends up through the brain for a distance of 5.5cm, connecting the ‘lower’ and ‘upper’ streams of the visual pathway. These run in parallel, and are sometimes called the ‘What’ and ‘Where’ pathways, for the type of information they carry: the lower stream, connects brain regions involved in processes such as object recognition, including the fusiform gyrus, and the upper stream connects the angular gyrus to other areas involved in attention, motion detection, and visually-guided behaviour. The front portion of the VOF links the intraparietal sulcus, which encodes information about eye movements, to the occipito-temporal sulcus, which encodes representations of word forms. The portion further back links higher order visual areas within the two streams, which encode complex maps of the visual field. Given the functions of these brain regions, the researchers speculate that the VOF likely plays an important role in perceptual processes such as reading and recognising faces.”

It seems a pretty important piece of anatomy to have been lost for a 100 years.


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