The human brain is alive with currents created when neurons fire to communicate with other neurons.
German neurologist Hans Berger found a way to read the current by developing what's known as an electroencephalograph. This kind of machine produces a graph measurement of brain waves, known as an electroencephalogram (EEG).
The system involves hooking up several pairs of electrodes on a patient's head. These electrodes are disks that conduct electrical activity, capture it from the brain and convey it out through a wire to a machine that amplifies the signal. Scientists attach electrodes in pairs on the head because they're measuring the difference in voltage between the pair. Soon after starting his research, Berger noticed that the electrical activity of brain waves correlated to a person's state of mind.
­Your brain waves are usually slowest during sleep. However, slow is relative. In deep sleep, the brain transmits delta waves, which fire one to four times per second. In light sleep, theta waves fire about four to seven times per second. Alpha waves, which we emit when we're in a relaxed, conscious state, come next at about seven to 13 pulses per second. Lastly, beta waves, which reflect a very excited or stressed mind, fire fastest at 13 to 40 times per second. The different types of waves are shown below.
Your brain doesn't emit just one kind of wave at one time; rather, it emits multiple kinds of waves simultaneously. Nevertheless, one kind of wave can dominate in a given moment.
­Today, doctors are able to use EEG tests for a variety of applications, such as diagnosing epilepsy as well as other seizure disorders. The test is appropriate for diagnosing epilepsy because the everyday brain wave patterns of patients with epilepsy tend to be abnormal. EEG tests can also reveal sleep disorders, tumours and the effects of a head injury or determine whether a coma patient has become brain dead.