A material that does not easily transmit energy, such as electric current or heat. Materials such as wood, plastic, and ceramics are insulators. Fiberglass is an example of a heat insulator. (Compare conductor.)
An electroencephalogram (EEG) is a noninvasive test that records electrical patterns in your brain. The test is used to help diagnose conditions such as seizures, epilepsy, head injuries, dizziness, headaches, brain tumors and sleeping problems.
An EEG, or electroencephalograph, is a test to measure brain activity. During an EEG, numerous electrodes in the form of patches are applied to the head. These electrodes detect the electrical activity in the brain, and a graph of that activity is generated.