Electroencephalography

Electroencephalography emerged in 1924 Jena not from a quest to understand the brain, but from one man's obsession with telepathy. Hans Berger, a German psychiatrist, had become convinced after a near-death experience in his youth that minds could communicate directly. He spent decades searching for the physical basis of psychic phenomena, and in doing so discovered that the brain generates continuous electrical activity that can be recorded from the scalp.

The adjacent possible for EEG had been forming for decades. In 1875, British physician Richard Caton had recorded electrical potentials from exposed animal brains, proving that neural tissue generated measurable signals. But recording through intact human skull and scalp required far more sensitive equipment. The string galvanometer that Einthoven had developed for electrocardiography in 1901 provided the necessary technology—a detector sensitive enough to capture the brain's far weaker signals.

Berger's first successful recording came on July 6, 1924, during a neurosurgical operation on a 17-year-old boy. With the skull already opened, Berger could place electrodes directly on the brain surface. Later, using silver foil electrodes attached to the scalp with rubber bandages, he demonstrated that recordings were possible through intact skull. He used first a Lippmann capillary electrometer, then a string galvanometer, and finally a Siemens double-coil recording galvanometer capable of detecting voltages as small as one ten-thousandth of a volt.

What Berger found surprised him. The brain didn't produce chaotic noise—it generated rhythmic oscillations. He identified what he called alpha waves, rhythmic patterns at 8-13 cycles per second that appeared when subjects closed their eyes and relaxed, then disappeared when they opened their eyes or concentrated. He had discovered the electrical signature of consciousness itself.

Berger published his findings in 1929, five years after his initial success. The scientific community ignored him. A German psychiatrist claiming to read brain waves seemed to border on mysticism. Only after British electrophysiologists Edgar Adrian and B.H.C. Matthews independently confirmed his observations in 1934 did the importance of EEG gain recognition at an international forum in 1937.

The technology demonstrates profound niche construction. Once scientists could see brain waves, they discovered that different brain states produced different patterns. Sleep had distinct stages visible in EEG traces. Epilepsy showed characteristic spike-and-wave patterns. Tumors disrupted normal rhythms. Each discovery created new applications, which drove demand for better equipment, which enabled more discoveries.

Berger never found evidence for telepathy. But his quixotic search created a keystone technology for neuroscience and neurology. Modern EEG machines, using digital signal processing and dense electrode arrays, continue the work he began with string galvanometers and rubber bandages, revealing the brain's electrical symphony in ever-finer detail.