Definitions for EEG – EEG Exam Questions and Answers 100% Pass

Definitions for EEG – EEG Exam Questions and Answers 100% Pass Electroencephalogram - An instrument that generates a record of the electrical activity of the brain by measuring electric potentials using electrodes attached to the scalp. Electroencephalograph - A chart of the brain waves picked up by the electrodes placed on the scalp. 10-20 System - A system of electrode application on the scalp using identifiable skull landmarks as reference. Distributed using percentages of 10 and 20. Montage - The particular arrangement by which a number of derivations are displayed simultaneously in an EEG record. Bipolar Montage - Chains of derivations that consist of electrodes along the same array, where input 2 in one channels in input 1 in the next. Transverse Montage - A montage consisting of derivations from pairs along coronal (transverse) arrays. Also called a Coronal Bipolar Montage. Longitudinal Montage - A montage consisting of derivations from pairs of electrodes along longitudinal, usually anterior to posterior, arrays. 2 | P a g e Author. Emily Charlene, ©2025 All Rights Reserved. Reference Montage - An arrangement of derivations in which one input 2 is common to all channels. Derivation - A pair of electrodes recorded in the EEG. Polarity - The sign of potential different between an electrode affected by the given potential and another electrode. Artefact - Any potential difference due to an extracerebral source (either physiological or mechanical) recorded in EEG tracings. Frequency - The rhythmic repetitive activity or the equivalent frequency of isolated waves. Rhythmic - A constant frequency. Arrhythmic - A sequence of waves of inconstant frequency. Voltage - The amplitude of a waveform. Refers to the average voltage or peak voltage of EEG activity. Attenuation - The reduction of amplitude of EEG activity resulting from decreased voltage. Hypersynchrony - An increase in voltage and regularity of rhythmic activity. Paroxysmal - Activity that emerges from the background with a rapid onset. Morphology - The shape of a waveform. Monomorphic - One dominant waveform. Polymorphic - Multiple frequencies that combine to form a complex waveform. Sinusoidal - Waves resembling sine waves. Monomorphic activity is usually sinusoidal. Transient - An isolated wave or pattern that is distinctly different from the background activity. Spike - A transient waveform with a pointed peak and duration of 20-70 milliseconds. 3 | P a g e Author. Emily Charlene, ©2025 All Rights Reserved. Sharp wave - A transient waveform with a pointed peak and duration of 70-200 milliseconds. Complex - A sequence of 2 or more waves, not necessarily of the same frequency, with a distinct form or pattern different from the background. Biphasic - A wave or complex having 2 distinct components, one surface positive and the other surface negative. Triphasic - A wave or complex with 3 distinct components, such as (+-+) or (-+-). Quantity - The amount of a particular type of EEG activity with respect to percentage time present and or voltage. Continuous - Occurring without interruption. Discontinuous - Appearing from time to time. Also called intermittent Irregular Quantity - Inconsistent frequency Regular Quantity - Consistent freqency Location - Refers to the scalp distribution of the EEG rhythms. Generalized - Not limited to a specific area of the brain. Lateralized - Coming from one side of the head; asymmetric. Bilateral - Coming from both sides of the head (homologous ar