Shielded Coaxial Optrode Arrays for Neurophysiology.

Jeffrey R Naughton,Michael J Naughton,Juan A Varela,Timothy Connolly,John P Christianson,Jaclyn Lundberg,Thomas C Chiles,Michael J Burns

doi:10.3389/fnins.2016.00252

Abstract

Recent progress in the study of the brain has been greatly facilitated by the development of new tools capable of minimally-invasive, robust coupling to neuronal assemblies. Two prominent examples are the microelectrode array (MEA), which enables electrical signals from large numbers of neurons to be detected and spatiotemporally correlated, and optogenetics, which enables the electrical activity of cells to be controlled with light. In the former case, high spatial density is desirable but, as electrode arrays evolve toward higher density and thus smaller pitch, electrical crosstalk increases. In the latter, finer control over light input is desirable, to enable improved studies of neuroelectronic pathways emanating from specific cell stimulation. Here, we introduce a coaxial electrode architecture that is uniquely suited to address these issues, as it can simultaneously be utilized as an optical waveguide and a shielded electrode in dense arrays. Using optogenetically-transfected cells on a coaxial MEA, we demonstrate the utility of the architecture by recording cellular currents evoked from optical stimulation. We also show the capability for network recording by radiating an area of seven individually-addressed coaxial electrode regions with cultured cells covering a section of the extent.

Highlights

A major goal of neurophysiology is to understand how ensembles of neurons generate, store and recall representations of the physical world and coordinate responses to its changing environment
Comparing the overlapping profile regions in each of the regimes shown, it can be seen that the field near bare electrodes overlaps that of its neighbors, while this overlap is suppressed for shielded electrodes
By approximating the proximity of an electrogenic cell to our electrode array to be 50 nm (Fromherz, 2003a), we were able to obtain a range of shield heights appropriate for sensitive extracellular action potentials (APs) recording and crosstalk suppression

Summary

Introduction

A major goal of neurophysiology is to understand how ensembles of neurons generate, store and recall representations of the physical world and coordinate responses to its changing environment To understand these fundamental capacities, neuroscientists investigate the electrical activity of neurons in individual and networked form to correlate patterns of activity to specific behaviors or cognitions. Many years of device development and refinement have produced state-of-the-art tools capable of measuring action potentials (APs) originating from multiple neurons, as well as tracking propagation of APs (Blanche et al, 2005; Bakkum et al, 2013; Buzsáki et al, 2015) One such tool is the microelectrode array (MEA), which is highly scalable and able to be utilized in a multiplex assay, the type necessary to study ensembles of neurons (Hierlemann et al, 2011). In some cases, such technologies have brought the electrode pitch down to the 20 micron range (Hutzler et al, 2006; Frey et al, 2010)

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Results

Conclusion