Basic Techniques of Evoked Potential Recording
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This chapter starts with defining different types of electrical activities recordable from peripheral and central nervous system, including stimulus-related and event-related evoked potentials (EPs). The basic EP equipment includes stimulators, amplifiers/filter system, and analog to digital (AD) converter/averager. The chapter emphasizes the characteristics of an ideal stimulus to elicit EPs, basic principles of AD conversion (sampling and quantization), and the principles of horizontal and vertical resolution. Signal averaging to improve signal-to-noise ratio is discussed in detail including limitation of signal averaging and strategies to improve EP recording. Different systems of naming EP components and different possible ways of measuring latency and amplitudes of EP components are discussed. The need for each laboratory to obtain its own normative data is emphasized as well as how to utilize the one-sided tolerance limit to set up the laboratory’s upper limit of latency values. The basic principles underlying appropriate use of analysis time, stimulus rate, filters, sampling rate, AD converter bits, and number of the averages are discussed for the EPs. Finally, the concept of near-field and far-field evoked responses is introduced and why a proper montage need to be designed to satisfactorily record these two different types of responses.
KeywordsStimulus-related evoked potentials AD conversion Signal enhancement Principles of averaging EP nomenclature Normative EP data Tolerance limits Near- and far-field responses
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