Final answer:
EEGs are tests that measure electrical brain activity through electrodes placed on the head, showing wave frequency and amplitude, useful for studying sleep patterns and other neurological conditions.
Step-by-step explanation:
The electrical outputs that indicate levels of activity in brain neurons are referred to as electroencephalograms or EEGs. An EEG is a test that measures the electrical activity of the brain using an array of electrodes placed around a person's head.
This test can show both the frequency, which is the number of waves per second measured in Hertz (Hz), and the amplitude, the height of the brainwaves, with an accuracy within milliseconds. The brainwaves recorded by an EEG are critical for studying various brain states like sleep, seizures, and other neurological conditions.
Sleep, for instance, is composed of different stages which can be distinguished by patterns of brain wave activity. Non-REM and REM stages of sleep show distinctive brainwaves that are visualized using an EEG. The understanding of these activity patterns is crucial for diagnosing and researching sleep disorders and other brain-related issues.