We often think of thoughts as instantaneous, but in truth it stands to reason that they are limited by the speed of certain chemical reactions and electrical impulses in our brain. Given that these physical activities accompany thinking, it also stands to reason that if one looks hard enough, one should be able to measure the electrical activity, despite the seemingly fleeting nature of brain activity The recording of these impulses—or electroencephalography—matured at something of a snail's pace until the work of Hans Berger (1873-1941).
In 1875, English physician Richard Caton figured out that he could measure brain activity in animals with a galvanometer. A Polish physician, Adolph Beck, also working with animals, advanced the topic further in the 1890s, going so far as to discover the location of some sensory impulses and noting a change in activity that took place with loud noises or bright light. The link between animal and human models was not well understood in this era, however, and it took a few more decades before anyone made this leap.
Hans Berger began experimenting with recording the electrical activity of the brain in the 1920s. Experimenting in secret, and oddly using lectures on telepathy as a cover, he refined his technique. Using his own son Klaus as a research subject, Berger recorded the first human electroencephalograph, or EEG, in 1924 and carried on his experiments for the next few years. Berger published his work in 1929 and revolutionized the world of neurology. EEG is used today to evaluate epilepsy, sleep disorders, and a host of other neurologic problems.
