Because he and his colleagues couldn't find any mention of this structure in medical literature, they thought it might be a new discovery. But when they reached out to others in the field, they heard back from one scientist who vaguely remembered this bundle of nerves — from an old medical textbook.

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A really old medical textbook. To track down the piece of brain's initial discovery, Yeatman and his colleagues had to dig into texts from the turn of the 20th century.

It was revealed as the vertical occipital fasciculus (VOF), discovered by a German neurologist named Carl Wenicke and included in his 1881 brain atlas. Yeatman could have stopped there, having found the right man to credit in his research papers. But he was intrigued by the structure's 10o-year-long disappearance from academic literature. "That started us on this fascinating detective mission figuring out how this brain anatomy got forgotten," he said.

It took a year of digging through Stanford's archives, but he solved the mystery. When Wernicke discovered the VOF, he may have ticked off his mentor, the neuroanatomist Theodor Meynert.

Meynert had theorized that all neural pathways moved from front to back across the brain — horizontally. But the VOF travels vertically, so its existence messed with Meynert's beliefs, which were generally accepted among scientists of the time.

For whatever reason, Meynert never discussed the VOF the way he did other structures discovered by Wernicke. It's possible that the structure just didn't interest him, however, as opposed to him snubbing his student intentionally.

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Without a signal boost from Meynert, the structure remained obscure. Others observed it, but they didn't call it by the same name, or described it differently because of their dissection techniques.

"Imagine being a student at the time, and trying to decipher this," Yeatman said. "Some people are saying the structure doesn't exist or are arguing about it, and some are giving it different names." He thinks that the confusion kept anyone from recognizing the VOF in modern textbooks.

Though obscure, the VOF may turn out to be very important.