Review of signal distortion through metal microelectrode recording circuits and filters

Abstract

Interest in local field potentials (LFPs) and action potential shape has increased markedly. The present work describes distortions of these signals that occur for two reasons. First, the microelectrode recording circuit operates as a voltage divider producing frequency-dependent attenuation and phase shifts when electrode impedance is not negligible relative to amplifier input impedance. Because of the much higher electrode impedance at low frequencies, this occurred over frequency ranges of LFPs measured by neurophysiologists for one head-stage tested. Second, frequency-dependent phase shifts are induced by subsequent filters. Thus, we report these effects and the resulting amplitude envelope delays and distortion of waveforms recorded through a commercial data acquisition system and a range of tungsten microelectrodes. These distortions can be corrected, but must be accounted for when interpreting field potential and spike shape data.

Oscillatory Entrainment of Thalamic Neurons by Theta Rhythm in Freely Moving Rats

“…Next we estimated the role of electrode impedance on the recorded signal. We analyzed the resistance values of the recording setup to evaluate the effect of the electrode impedance on the voltage sensed by the amplifier (Nelson et al 2008). Because the resistance of the amplifier (Ͼ10 M⍀) used in our study (Axona and A-M System) is much larger than the electrode resistance, we can conclude that the effect of electrode impedance on the signal amplitude is negligible.…”

Neural Correlates of Correct and Errant Attentional Selection Revealed Through N2pc and Frontal Eye Field Activity

“…The other half of monkey Q's data and nearly all of monkey S's data were band-pass filtered between 0.2 and 300 Hz, amplified using a Plexon high-impedance HST/8o50-G1 head-stage. The differences in head-stage may account for the slight difference in visually evoked LFP polarization between the monkeys as low impedance head-stages are known to create distortions in LFPs (Nelson et al 2008).…”

Using a Common Average Reference to Improve Cortical Neuron Recordings From Microelectrode Arrays

“…Typically either an additional microelectrode, or a large electrode such as a stainless-steel bone screw, or stripped wire, is placed in a location with minimal cortical activity and used as a reference to subtract out correlated sources of noise (Blanche et al 2005;Henze et al 2000;Ludwig et al 2006;Nelson et al 2008;Vetter et al 2004;Webster 1998;Williams et al 1999). Both microelectrode and large electrode references have their own specific advantages and disadvantages.…”