Factors affecting the stimulus artifact tail in surface-recorded somatosensory-evoked potentials

Abstract

Surface-recorded somatosensory-evoked potentials (SEPs) are neural signals elicited by an external stimulus. In the case of electrically induced SEPs, the artifact generated by the stimulation process can severely distort the signal. In some cases, the artifact tail often lasts well into the initiation of the SEP making the determination of absolute latency very difficult. In this work, a new approach was taken to identify factors that affect the tail of the artifact. The methodology adopted was the development of a lumped electrical circuit model of the artifact generation process. While the modeling of the instrumentation hardware is relatively simple, this is not the case with tissue and electrode/skin interface effects. Consequently, this paper describes a novel tissue modeling approach that uses an autoregressive moving average (ARMA) parametric technique and an artificial neural network (ANN) to estimate tissue parameters from experimental data. This coupled with an estimation of the stimulation electrode-skin impedance completes the lumped circuit model. Simulink (The Mathworks Inc.) was used to evaluate the model under several different conditions. These results show that both the stimulation electrode-skin interface impedance and nature of the body tissue directly under the recording electrodes have a profound effect on the appearance of the stimulus artifact tail. This was verified by experimentally recorded data obtained from the median nerve using surface electrodes. Conclusions drawn from this work include that stimulation electrodes with low series capacitance should be used whenever possible to minimize the duration of the artifact tail.

Optic nerve potentials and cortical potentials after stimulation of the anterior visual pathway during neurosurgery

“…The complex features of the stimulus artifact in our series are postulated to depend on the characteristics of the stimulator, amplifier, and filter; stimulating and recording electrode characteristics and the degree of electromagnetic coupling between them; the direct effect of the stimulus current on the surrounding brain tissue; the impedance of the tissues of the skull; and the path of the displacement current [28][29][30]. Under unique intraoperative recording conditions, we were unable to diminish the stimulus artifact after modifying the pertinent parameters of the intraoperative neurophysiological monitoring system; employing a different intraoperative neurophysiological monitoring system; and utilizing several different types of stimulating and recording electrodes.…”

A novel fully fast recovery EMG amplifier for the control of neural prosthesis

“…For optimal stimulus artefact reduction, the EMG amplifier should be turned-off before stimulation pulse and turned-on after stimulation pulse [18].…”

Stimulus artifact reduction in somatosensory evoked potential measurements using velocity filters

“…The SA is a manifestation of the stimulus pulse that appears at the recording site after propagating through the tissue. the SEP latency and causes significant distortion to the SEP measurement [1], [2], [13].…”

“…The SA normally has a large initial spike, followed by a slowly decaying tail component [6], [13]. Although the large spike portion of the SA is fairly localized in time and short in duration, it is the slow tail component that usually temporally overlaps the SEP.…”

“…It is generally accepted that the SA generation mechanism contains nonlinearities and exhibits large variability across different subjects and different locations within a subject, [2], [13]. Therefore, the SA generation mechanism is not easily modeled in accurate detail.…”