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.
How EEG works. 1  EEG, or electroencephalogram, is a tool we use to image the brain while it is performing a cognitive task. This allows us to detect the location and magnitude of brain activity involved in the various types of cognitive functions we study.