In our invertebrate experiments, we recorded spikes directly from exposed neurons. In humans, the skull protects the brain, making direct access to neurons impossible without invasive techniques. This is where EEG comes in—a method that detects the collective electrical activity of many neurons through electrodes placed on the scalp. These signals, while weaker and slower due to passing through bone, skin, and hair, reveal fascinating patterns about how the brain works.

The story of EEG begins with a dramatic event. In the 1920s, German psychiatrist Hans Berger was thrown from his horse in a military accident. At the same time, miles away, his sister reportedly felt a sudden fear for his safety and sent him a telegram to check if he was all right. Berger became captivated by this coincidence and set out to explore whether the brain could communicate in ways beyond the ordinary senses—what some might call telepathy.

Although he never found evidence of ESP, his experiments led to the groundbreaking discovery that the brain generates electrical rhythms detectable on the scalp. He realized that these rhythms change depending on what the brain is doing, particularly when the eyes are open versus closed.

Now it’s your turn to explore. Using EEG, you’ll record brain activity while alternating between open and closed eyes. Look closely at the patterns. What changes when the eyes are closed? What might this tell us about how the brain responds to visual input—or the lack of it? This is your chance to investigate and form your own conclusions, just as Hans Berger did nearly a century ago.