When Hans Berger was serving a year in the German military, in 1892, he was thrown from a horse. This in itself wasn't strange. But later that day, as the neurologist David Millett recounts in Perspectives in Biology and Medicine, Berger got a telegram from his father, just checking on his well being. Berger's father had never sent him a telegram before. But his older sister had just had a feeling …

For Berger, this uncanny encounter determined a lifetime of research in medicine and psychology. How did the brain—the mind—interact with the outside world? What was it that prompted his sister to worry about him that day and tell his father to check in on him? He began his work trying to understand and measure the psychic energy of the brain.

Only recently, though, have researchers really begun to understand what gives rise to uncanny feelings in the brain, and though Berger's research project began grandly, it narrowed, over decades, to a much simpler goal—he wanted to record the electrical signals of the brain. By the time he started seriously on this quest, Berger had already tried to measure blood flow and heat in the brain and correlate those changes with neurological stimuli. His work was quixotic, and in the German town where he lived, his colleagues were skeptical of his obsession.

One colleague, Raphael Ginzberg—who was supportive of his work—would later write:

In the small medical world of Jena, nobody, least of all Berger's associates, expected him to make a great scientific discovery … His days resembled one another like two drops of water. Year after year he delivered the same lectures. He was the personification of static.

But, in the mid-1920s, Berger succeeded. He recorded the electrical waves of the brain. Millett writes:

"These first recordings of the human EEG are remarkably unimpressive: coarse shadows of minute oscillations on the galvanometer string captured on photographic paper. There was no hint of the large alpha waves, wave and spike complex, or other characteristic waveforms that would be recognized among standard EEG records within a few years."

Berger kept refining his process and by 1929, he was regularly producing legible EEGs. He kept experimenting, with silver foil electrodes that went on subjects' scalp or chlorided silver needles that went into subjects' skulls. He performed 73 scalp EEGs on his son, Klaus, whose hair was cut short. He took 56 from himself—often, using the needles. Throughout all this, his colleagues were still skeptical of his work—those faint traces of electrical activity in the brain just didn't seem like they could be real.

They were—EEGs underlie the brain-computer interfaces that today allow people give commands to mechanical devices with their minds—and Berger had pioneered their measurement all on his own. As Ginzberg put it: "He let nobody into the secret of his investigation. What he achieved, he achieved by his individual effort."

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