If your family is anything like mine, you have that one crazy uncle with his tin foil hat, purportedly to prevent the aliens from electromagnetically manipulating his brain or to prevent his precious brain waves from being read by the government. While few take such fears seriously, significant confusion persists regarding ‘brain waves.’ What are they and where do they come from? Can they be picked up and decoded like radio signals, perhaps even useful for telepathy (or alien-monitoring of your thoughts)?
Your brain, like every other organ in your body, is composed of cells. Though other cell types play an important role, your abilities to perceive, act, reason, plan, and feel emotions are primarily due to the combined efforts of your approximately one hundred billion neurons. Unlike most cells, neurons have a complicated branching structure that allows them to form a bewildering number of connections with other neurons. Their main trick is the ability to send electrochemical signals down one of these branches, which can make connected cells more or less likely to fire a signal of their own (see here for a more technical definition). Whenever one of these signals reaches a target neuron, it creates a tiny electromagnetic disturbance in the surrounding area.
If all of the neurons in your brain were firing at random times, then we wouldn’t be able to detect electromagnetic changes outside the skull. Curiously, however, they don’t fire at random times. Neural activity follows certain cycles, known as oscillations. If you put an electrode on the outside of the scalp and plot the changes in the electric over time, you get a wave pattern like you see in the picture below, illustrating the combined effects of countless electrochemical signals.
These oscillations can cycle up and down at varying speeds, known as frequencies. Different frequencies appear to be associated with different brain regions and functions, leading researchers to classify oscillations into different frequency ‘bands.’ For instance, delta waves appear during deep sleep and complete a cycle between 1 and 4 times per second, while beta waves occur during concentration and cycle 13 to 30 times per second.
Hopefully it’s clear by now that brain waves constitute a massively aggregated signal, rather than a precise record of detailed brain states. An electrode on the scalp, like those used in electroencephalography (EEG), picks up the activity of tens of millions of neurons. This activity can inform an observer about the general state of a brain (is the person sleeping or alert?). Scientists can even use sophisticated computer programs to associate particular oscillatory patterns with some desired action, like the movement of a cursor on a screen. However, there is in principle not enough information present in these waves to read someone’s thoughts in a detailed way. Moreover, the electromagnetic ripples caused by your brain are quite small – it’s difficult to pick them up with electrodes on the scalp, let alone from an alien mothership. So while you can tell your uncle to exchange his headgear for something more stylish, we can learn a lot about brain function by measuring these waves in different circumstances.
Nancy Lundin is a graduate student in the department of Psychological and Brain Sciences here at IU. Some of her research with the Clinical and Cognitive Neuroscience Center focuses on using EEG setups like the one pictured above to better understand bipolar disorder. When most people are presented with an unusual stimulus, there is a quick burst of very fast oscillations, in what’s called the gamma, band followed by a burst of slower oscillations in the theta band. Her preliminary results suggest that this response is altered in people with bipolar disorder. Since we know a bit about the origin of gamma- and theta-band oscillations and the roles they play, this gives us some clues about what causes bipolar disorder and perhaps how we can treat it. Stay tuned for more information on the results of this study as it progresses!