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Bipolar versus Referential Derivations Name Institution Polysomnography (PSG) is the “recording of multiple neurophysiologic signals, simultaneously, in reference to the objectives of a clinician” (Friedman, 2014, p. 25). According to Marshall, Robertson, and Carno (2013), there is no type of derivation is recommended because various activities take place simultaneously and require different types of derivation. Two derivations of interest are the bipolar and referential derivations, which will be the topic of concern in this paper, as it seeks to compare and contrast their use in EEG and PSG. A bipolar derivation is when a pair of electrodes record from an active signal location while in a referential derivation, one electrode is the recording terminal while the one is a reference electrode that is not placed in a location with an active signal (Marshall et al., 2013). The referential recording is commonly used in polysomnography while bipolar recording is used in seizure patients to isolate sharp wave from spike activity. The referential recording is ideal for EEG derivations to aid in sleep staging by employing at least three channels: frontal, central, and occipital channels. The standard derivations are F4-M1, C4-M1, and O2-M1 which are recorded from an opposite hemisphere as F3-M2, C3-M2, and O1-M2 as backup for EEG. Frontal derivations help to enhance the visibility of slow wave activity while central derivations help to make the spindling activity and K-complexes more noticeable and enable occipital derivations to reduce alpha activity. Ultimately, the activity of all the three channeled derivations helps to identify sleep stages in a better way.