Abstract
ObjectivesIn this paper, we aim to detail the setup of a high spatio-temporal resolution, electrical recording system utilising planar microelectrode arrays with simultaneous optical imaging suitable for evaluating microelectrode performance with a proposed ′performance factor′ metric.MethodsTechniques that would facilitate low noise electrical recordings were coupled with voltage sensitive dyes and neuronal activity was recorded both electrically via a customised amplification system and optically via a high speed CMOS camera. This technique was applied to characterise microelectrode recording performance of gold and poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT/PSS) coated electrodes through traditional signal to noise (SNR) calculations as well as the proposed performance factor.ResultsNeuronal activity was simultaneously recorded using both electrical and optical techniques and this activity was confirmed via tetrodotoxin application to inhibit action potential firing. PEDOT/PSS outperformed gold using both measurements, however, the performance factor metric estimated a 3 fold improvement in signal transduction when compared to gold, whereas SNR estimated an 8 fold improvement when compared to gold.ConclusionThe design and functionality of a system to record from neurons both electrically, through microelectrode arrays, and optically via voltage sensitive dyes was successfully achieved.SignificanceThe high spatiotemporal resolution of both electrical and optical methods will allow for an array of applications such as improved detection of subthreshold synaptic events, validation of spike sorting algorithms and a provides a robust evaluation of extracellular microelectrode performance.
Highlights
The brain is one of the most intricate organs, functioning to control our physical senses, emotions and bodily processes
PEDOT/PSS outperformed gold using both measurements, the performance factor metric estimated a 3 fold improvement in signal transduction when compared to gold, whereas signal to noise ratio (SNR) estimated an 8 fold improvement when compared to gold
We present schematics for a low noise amplifier to acquire high quality electrical recordings from microelectrode arrays (MEAs) devices as well as optimised voltage sensitive dyes (VSDs) protocols and imaging techniques using a high speed CMOS camera
Summary
The brain is one of the most intricate organs, functioning to control our physical senses, emotions and bodily processes. The last decade has seen a surge of research which aims to interface these neural networks with electrode arrays in order to monitor and affect diseased pathways at an in vitro level through microelectrode arrays (MEAs) and an in vivo level through implantable electrode arrays [1] The rationale behind this approach is that electrodes can correct or stimulate activity in certain neurons through a current pulse which causes depolarisation or hyperpolarisation of the cell [2]. At the front-line of these devices are electrodes which interface with the neuron to record or stimulate activity They are typically made of noble metal materials, such as platinum, but the demand for smaller electrodes to achieve high spatiotemporal resolution has strained the performance of these materials through a subsequent increase in impedance [3]. Materials which have received the most attention due to superior electrochemical performance, stability and biocompatibility include poly(3,4-ethylenedioxythiophene) (PEDOT) [4,5,6,7,8], carbon nanotubes (CNTs) [9,10,11], glassy carbon [12], iridium oxide (IrOx) [13, 14] and nanostructured platinum [13, 15]
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