Final answer:
An EEG measures the electrical activity of the brain by using electrodes to detect brainwaves and represents this data as frequency and amplitude on a printout. It is different from MRI and fMRI, which image brain structure and measure changes in brain tissue activity, respectively.
Step-by-step explanation:
An EEG, or electroencephalography, measures the electrical activity of the brain. This is achieved by placing an array of electrodes around the person's head to detect brainwaves, which are depicted in a printout showing the frequency and amplitude of the waves, providing accuracy within milliseconds. This technique can offer researchers valuable insights into various brain-related conditions and activities, such as sleep patterns in individuals with sleep disorders.
The EEG is different from procedures like MRI or fMRI, as those techniques provide images of brain structure and activity changes within the tissue over time, respectively. Another similar technique that measures electrical activity is ECG (electrocardiogram), which records the electrical impulses of the cardiac muscle, showing the health and function of the heart.