Effects of Electrode Size on Extracellular Recordings of Neural Activity
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1
ETH Zürich, D-BSSE, Switzerland
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2
MaxWell Biosystems, Switzerland
Extracellular electrodes constitute a popular technique for long term in vitro and in vivo recording of the electrical activity of large neuronal ensembles (Buzsáki 2004). For in vitro extracellular recording of cell cultures and tissues microelectrode arrays (MEAs) enable simultaneous multisite recording which is essential to study cellular interconnections and network properties. Recently, simultaneous recordings from very large numbers of neurons as well as signals of subcellular compartments have been acquired through the use of micrometer-size-electrodes in high-density arrays, arranged over a comparably large area. Although the mechanism of recording extracellular signals from neurons through planar metal electrodes has been thoroughly studied (Robinson 1964; Franks 2005) the effects of the electrode characteristics on the recorded signal, especially for small electrode sizes (< 10 μm diameter), is yet to be fully established. Here, we present a combined experimental and computational approach to elucidate how electrode size influences neuronal signals and how inherent properties of the electrode, such as impedance, noise, and transmission characteristics shape the recorded signal.
We first studied the signal-acquisition process in detail, from the electrode interface to signal digitization. Three main components influence the recording performance of extracellular electrodes: the characteristics of (1) the neuronal cell type, (2) the recording electrode, and (3) the readout hardware. The neuronal signals of interest are attenuated along the overall recording chain and will be compromised by noise until they get digitized and stored for analysis. We recorded from different cell types (acute cerebellar slices, cortical neurons in dissociated cell cultures, and hippocampal neurons in organotypic slice cultures) with thousands of electrodes of different sizes and in the same preparation to characterize the performance of these electrodes for different measurement scenarios.
We characterized the electrode performances for both, local-field-potential (LFP) and extracellular-action-potential (EAP) recording. We demonstrate that, provided a set of requirements for the signal amplification is met, good signal-to-noise ratio can be achieved with electrode diameters between 1 and 8 µm for detecting propagating action potentials along axonal branches; between 8 and 30 µm for EAP recording from individual neurons; and with diameters larger than 16 µm for LFP recording from local groups of neurons or networks. Our findings can be used as a guide for selecting electrode configurations of neural probes or electrode arrays to serve a specific application.
Acknowledgements
Financial support through the H2020 ERC Advanced Grant 2015 - 694829 “neuroXscales”, (Microtechnology and integrated microsystems to investigate neuronal networks across scales) is acknowledged.
References
• Buzsáki, György. 2004. “Large-Scale Recording of Neuronal Ensembles.” Nature Neuroscience 7 (5): 446–51. doi:10.1038/nn1233.
• Robinson, D. A. The electrical properties of metal microelectrodes. Proc. IEEE 56, 1065–1071 (1968).
• Franks et al, A. Impedance characterization and modeling of electrodes for biomedical applications. IEEE Trans. Biomed. Eng. 52, 1295–1302 (2005).
Keywords:
Electrode size,
Microelectrode arrays (MEAs),
extracellular recording,
electrode impedance,
electrode noise
Conference:
MEA Meeting 2018 | 11th International Meeting on Substrate Integrated Microelectrode Arrays, Reutlingen, Germany, 4 Jul - 6 Jul, 2018.
Presentation Type:
Poster Presentation
Topic:
Microelectrode Array Technology
Citation:
Viswam
V,
Obien
MJ,
Frey
U,
Franke
F and
Hierlemann
A
(2019). Effects of Electrode Size on Extracellular Recordings of Neural Activity.
Conference Abstract:
MEA Meeting 2018 | 11th International Meeting on Substrate Integrated Microelectrode Arrays.
doi: 10.3389/conf.fncel.2018.38.00098
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Received:
17 Mar 2018;
Published Online:
17 Jan 2019.
*
Correspondence:
Dr. Vijay Viswam, ETH Zürich, D-BSSE, Zurich, Basel, Switzerland, vijay.viswam@mxwbio.com