BIOPOTENTIAL AMPLIFIERS - Design and Development of Medical Electronic Instrumentation - page 40

Figure 1.33 Bipolar array recording of composite propagating EMG activity evoked by a single surface stimulation pulse. The artifact
resulting from stimulation currents and switching discontinuity is indicated between brackets. [Reprinted from Med. Eng. Phys. , 17, D.
Prutchi, A High-Resolution Large Array (HRLA) Surface EMG System, pages 442-454, 1995, with permission from Elsevier.]

is present on all channels simultaneosly. Please note that the level of interference it causes
(shown between brackets) is minimal compared to the amplitude of evoked potentials.
Recently, multichannel recordings such as these have gained wide popularity in
research and diagnostic uses of electrophysiological activity. For example, 32-channel sys-
tems have been used in EEG and evoked potentials, and 64-channel systems have been
developed for body potential mapping (BPM) ECG. In electromyography, surface elec-
trode arrays have been used to detect propagating electrical activity in skeletal muscles,
enabling noninvasive estimation of muscle fi fiber conduction velocity and innervation zone.

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