A comparative study of electrical potential sensors and Ag/AgCl electrodes for characterising spontaneous and event related electroencephalagram signals.
BACKGROUND
Electroencephalography (EEG) is still a widely used imaging tool that combines high temporal resolution with a relatively low cost. Ag/AgCl metal electrodes have been the gold standard for non-invasively monitoring electrical brain activity. Although reliable, these electrodes have multiple drawbacks: they suffer from noise, such as offset potential drift, and usability issues, for example, difficult skin preparation and cross-coupling of adjacent electrodes.


METHODS
In order to tackle these issues a prototype Electric Potential Sensor (EPS) device based on an auto-zero operational amplifier was developed and evaluated. The EPS is a novel active ultrahigh impedance capacitively coupled sensor. The absence of 1/f noise makes the EPS ideal for use with signal frequencies of ∼10Hz or less. A comprehensive study was undertaken to compare neural signals recorded by the EPS with a standard commercial EEG system.


RESULTS
Quantitatively, highly similar signals were observed between the EPS and EEG sensors for both free running and evoked brain activity with cross correlations of higher than 0.9 between the EPS and a standard benchmark EEG system.


CONCLUSIONS
These studies comprised measurements of both free running EEG and Event Related Potentials (ERPs) from a commercial EEG system and EPS.


CONCLUSIONS
The EPS provides a promising alternative with many added benefits compared to standard EEG sensors, including reduced setup time and elimination of sensor cross-coupling. In the future the scalability of the EPS will allow the implementation of a whole head ultra-dense EPS array.
Department of Engineering and Design, University of Sussex, Brighton BN1 9QJ, UK. Electronic address: M.Fatoorechi@sussex.ac.uk.
M
M
Fatoorechi
Sackler Centre for Consciousness Science, University of Sussex, Brighton BN1 9QJ, UK; School of Psychology, University of Sussex, Brighton BN1 9QH, UK.
J
J
Parkinson
Department of Engineering and Design, University of Sussex, Brighton BN1 9QJ, UK.
R J
RJ
Prance
Department of Engineering and Design, University of Sussex, Brighton BN1 9QJ, UK.
H
H
Prance
Sackler Centre for Consciousness Science, University of Sussex, Brighton BN1 9QJ, UK; Department of Informatics, University of Sussex, Brighton BN1 9QJ, UK.
A K
AK
Seth
Sackler Centre for Consciousness Science, University of Sussex, Brighton BN1 9QJ, UK; Department of Informatics, University of Sussex, Brighton BN1 9QJ, UK.
D J
DJ
Schwartzman
D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000295:instrumentation / Q000379:methods; D058256:Brain Waves / Q000502:physiology*; D017097:Electric Impedance; D004566:Electrodes; D004569:Electroencephalography; D004867:Equipment Design; D005071:Evoked Potentials / Q000502:physiology*; D006801:Humans; D010775:Photic Stimulation; D013057:Spectrum Analysis; D014796:Visual Perception / Q000502:physiology*
Capacitive electrode; EEG; ERP; Electrical potential sensor; ud-EEG