Abstract
Electrophysiology is a decades-old technique widely used for monitoring activity of individual neurons and local field potentials. Optogenetics has revolutionized neuroscience studies by offering selective and fast control of targeted neurons and neuron populations. The combination of these two techniques is crucial for causal investigation of neural circuits and understanding their functional connectivity. However, electrical artifacts generated by light stimulation interfere with neural recordings and hinder the development of compact closed-loop systems for precise control of neural activity. Here, we demonstrate that transparent graphene micro-electrodes fabricated on a clear polyethylene terephthalate film eliminate the light-induced artifact problem and allow development of a compact battery-powered closed-loop optogenetics system. We extensively investigate light-induced artifacts for graphene electrodes in comparison to metal control electrodes. We then design optical stimulation module using micro-LED chips coupled to optical fibers to deliver light to intended depth for optogenetic stimulation. For artifact-free integration of graphene micro-electrode recordings with optogenetic stimulation, we design and develop a compact closed-loop system and validate it for different frequencies of interest for neural recordings. This compact closed-loop optogenetics system can be used for various applications involving optogenetic stimulation and electrophysiological recordings.
Highlights
Electrophysiology has been the backbone of neuroscience research for decades
We present a compact battery-powered closed-loop optogenetics system enabled by transparent graphene electrode array
We have adopted and refined the “bubbling” transfer method (Wang et al, 2011; Gao et al, 2012), with which monolayer graphene grown on 20 μm thick copper foil with chemical vapor deposition (CVD) was transferred on polyethylene terephthalate (PET) substrate
Summary
Electrophysiology has been the backbone of neuroscience research for decades. The last decade has witnessed rapid advancements in multi-photon imaging methods for monitoring hundreds of cells densely packed in neuronal microcircuits with high resolution. The advent of optogenetics has revolutionized neuroscience research by enabling selective control of neural activity and casual manipulation of specific neural circuits. Crosstalk-free integration of optical imaging, optogenetics and electrophysiological recordings can transform spatiotemporal mapping of neural circuits and can allow unprecedented studies of functional neural connectivity. Transparent microelectrode arrays made of graphene have been used for multimodal probing of neural circuits using two-photon microscopy (Kuzum et al, 2014) and optogenetics (Park et al, 2014). The optical transparency of graphene has been shown to enable efficient delivery of light for imaging of neuronal populations with high spatial resolution while recording their neural activity by the graphene electrode with high temporal resolution
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