Electroencephalogram (EEG) is a diagnostic test that involves applying electrodes to the scalp’s surface to measure electricity generated by neural activity. EEG is most commonly used in investigation of seizures and sleep disorders. The brain functions primarily via action potentials that lead to the release of neurotransmitters into synaptic clefts. Although an EEG cannot detect the tiny amount of electricity produced by individual neurons, visible waves or spikes are generated when clusters of neurons fire together. These voltages are very small – just a few millionths of a volt. These neural oscillations are popularly called brain waves.