Review of signal distortion through metal microelectrode recording circuits and filters

doi:10.1016/j.jneumeth.2007.12.010

Journal of Neuroscience Methods

Volume 169, Issue 1, 30 March 2008, Pages 141-157

https://doi.org/10.1016/j.jneumeth.2007.12.010 Get rights and content

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.

Section snippets

Equivalent circuit model

Fig. 1 illustrates a modified version of a commonly cited equivalent circuit model of a metal microelectrode recording in the brain (Robinson, 1968). The effective electrode impedance ( ${Z^{'}}_{e}$ ) is the sum of impedances due to the resistance of the electrolyte (R_s), the resistance of the electrode metal (R_m) and, most importantly, the resistance and capacitance at the double layer that forms at the electrode/electrolyte interface at the uninsulated electrode tip (R_e and C_e). The effective amplifier

Determination of amplifier input impedance

To verify that the equivalent circuit model applies to microelectrode recordings, we measured the input impedance for two head-stages, one with lower and one with higher input impedance. To do this we measured V_rec with V_sig consisting of sine wave voltages (0.5 Hz–9 kHz) applied to the head-stage across different metallic resistances. Fig. 2 plots measurements made with the lower input impedance head-stage through a range of metallic resistors. The variation of gain (V_rec/V_sig) through the LFP

Summary

We have shown that signals recorded with tungsten microelectrodes and an acquisition system commonly used in neurophysiology can be distorted substantially from the actual signals at the electrode tip. This distortion consists of frequency-dependent phase shifts and amplitude attenuation. The system filters imposed noticeable phase shifts even within their passbands. The observed phase shifts were dependent on the exact specifications of the preamplifier selected for use in a given system. When

Disclosure statement

The authors affiliated with Vanderbilt University have no competing interests. The authors associated with Plexon have competing interests.

Acknowledgements

We would like to thank Justin Crouse at FHC for valuable discussions, Bruce Williams for construction of and assistance with the design of the electrode testing apparatus, and AB Bonds for valuable discussions and comments regarding the manuscript.

Grants: This work was supported by RO1-EY08890, Robin and Richard Patton through the E. Bronson Ingram Chair of Neuroscience and center grants P30-EY08126 and P30-HD015052.

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¹: Present address: Cyberkinetics, Foxborough, MA, USA.

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Review of signal distortion through metal microelectrode recording circuits and filters

Abstract

Section snippets

Equivalent circuit model

Determination of amplifier input impedance

Summary

Disclosure statement

Acknowledgements

Neuron

Neuron

Neuron

Characterization of neocortical principal cells and interneurons by network interactions and extracellular features

J Neurophysiol

Gamma (40–100 Hz) oscillation in the hippocampus of the behaving rat

J Neurosci

Introduction to bioelectrodes

Rapid feature selective neuronal synchronization through correlated latency shifting

Nat Neurosci

Modulation of oscillatory neuronal synchronization by selective visual attention

Science

Electrodes and the measurement of bioelectric events

The relationship between electrode area and amplifier input impedance in recording muscle action potentials

Med Biol Eng

The impedance of stainless steel electrodes

Med Biol Eng

On the origin of the extracellular action potential waveform: a modeling study

J Neurophysiol

A simple microelectrode for recording from the central nervous system

Nature

Bioimpedance & bioelectricity basics

Analysis of LFP phase predicts sensory response of barrel cortex

J Neurophysiol

Tungsten microelectrode for recording from single units

Science

Cellular-synaptic generation of sleep spindles, spike-and-wave discharges, and evoked thalamocortical responses in the neocortex of the rat

J Neurosci

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