Biology subjects

Richie, J. M.

Publications and source records attributed to Richie, J. M..

4 recordsLinked to original sources

bioRxiv2021

Carbon Fiber Electrodes for Intracellular Recording and Stimulation

To understand neural circuit dynamics, it is critical to manipulate and record from many neurons, ideally at the single neuron level. Traditional recording methods, such as glass microelectrodes, can only control a small number of neurons. More recently, devices with high electrode density have been developed, but few of them can be used for intracellular recording or stimulation in intact nervous systems, rather than on neuronal cultures. Carbon fiber electrodes (CFEs) are 8 micron-diameter electrodes that can be organized into arrays with pitches as low as 80 {micro}m. They have been shown to have good signal-to-noise ratios (SNRs) and are capable of stable extracellular recording during both acute and chronic implantation in vivo in neural tissue such as rat motor cortex. Given the small fiber size, it is possible that they could be used in arrays for intracellular stimulation. We tested this using the large identified and electrically compact neurons of the marine mollusk Aplysia californica. The cell bodies of neurons in Aplysia range in size from 30 to over 250 {micro}m. We compared the efficacy of CFEs to glass microelectrodes by impaling the same neurons cell body with both electrodes and connecting them to a DC coupled amplifier. We observed that intracellular waveforms were essentially identical, but the amplitude and SNR in the CFE were lower than in the glass microelectrode. CFE arrays could record from 3 to 8 neurons simultaneously for many hours, and many of these recordings were intracellular as shown by recording from the same neuron using a glass microelectrode. Stimulating through CFEs coated with platinum-iridium had stable impedances over many hours. CFEs not within neurons could record local extracellular activity. Despite the lower SNR, the CFEs could record synaptic potentials. Thus, the stability for multi-channel recording and the ability to stimulate and record intracellularly make CFEs a powerful new technology for studying neural circuit dynamics.

neuroscience↗

bioRxiv2021

Benchtop Carbon Fiber Microelectrode Array Fabrication Toolkit

BackgroundConventional neural probes are primarily fabricated in a cleanroom, requiring the use of multiple expensive and highly specialized tools. New methodWe propose a cleanroom "light" fabrication process of carbon fiber neural electrode arrays that can be learned quickly by an inexperienced cleanroom user. This carbon fiber electrode array fabrication process requires just one cleanroom tool, a parylene-c deposition machine, that can be learned quickly or outsourced to a commercial processing facility at marginal cost. Our fabrication process also includes hand-populating printed circuit boards, insulation, and tip optimization. ResultsThe three different tip optimizations explored here (Nd:YAG laser, blowtorch, and UV laser) result in a range of tip geometries and 1kHz impedances, with blowtorched fibers resulting in the lowest impedance. While previous experiments have proven laser and blowtorch electrode efficacy, this paper also shows UV laser cut fibers can record neural signals in vivo. Comparison with existing methodsExisting carbon fiber arrays either do not have individuated electrodes in favor of bundles or require cleanroom fabricated guides for population and insulation. The proposed arrays use only tools that can be used at a benchtop for fiber population. ConclusionsThis carbon fiber electrode array fabrication process allows for quick customization of bulk array fabrication at a reduced price compared to commercially available probes.

bioengineering↗

bioRxiv2021

Sharpened and mechanically robust carbon fiber electrode arrays for neural interfacing

Bioelectric medicine treatments target disorders of the nervous system unresponsive to pharmacological methods. While current stimulation paradigms effectively treat many disorders, the underlying mechanisms are relatively unknown, and current neuroscience recording electrodes are often limited in their specificity to gross averages across many neurons or axons. Here, we develop a novel, durable carbon fiber electrode array adaptable to many neural structures for precise neural recording. Carbon fibers were sharpened using a reproducible blowtorch method that uses the reflection of fibers against the surface of a water bath. The arrays were developed by partially embedding carbon fibers in medical-grade silicone to improve durability. We recorded acute spontaneous electrophysiology from the rat cervical vagus nerve (CVN), feline dorsal root ganglia (DRG), and rat brain. Blowtorching resulted in fibers of 72.3 {+/-} 33.5 degree tip angle with 146.8 {+/-} 17.7 m exposed carbon. Silicone-embedded carbon fiber arrays were durable with 87.5% of fibers remaining after 50,000 passes. Observable neural clusters were recorded using sharpened carbon fiber electrodes from rat CVN (41.8 Vpp), feline DRG (101.1 Vpp), and rat brain (80.7 Vpp). Recordings from the feline DRG included physiologically-relevant signals from increased bladder pressure and cutaneous brushing. These results suggest that this carbon fiber array is a uniquely durable and adaptable neural recording device. In the future, this device may be useful as a bioelectric medicine tool for diagnosis and closed-loop neural control of therapeutic treatments and monitoring systems.

bioengineering↗

bioRxiv2020

Multi-channel intraneural vagus nerve recordings with a novel high-density carbon fiber microelectrode array

Autonomic nerves convey essential neural signals that regulate vital body functions. Recording clearly distinctive physiological neural signals from autonomic nerves will help develop new treatments for restoring regulatory functions. However, this is very challenging due to the small nature of autonomic nerves and the low-amplitude signals from their small axons. We developed a multi-channel, high-density, intraneural carbon fiber microelectrode array (CFMA) with ultra-small electrodes (8-9 m in diameter, 150-250 m in length) for recording physiological action potentials from small autonomic nerves. In this study, we inserted CFMA with up to 16 recording carbon fibers in the cervical vagus nerve of 22 isoflurane-anesthetized rats. We recorded action potentials with peak-to-peak amplitudes of 15.1-91.7 V and signal-to-noise ratios of 2.0-8.3 on multiple carbon fibers per experiment, determined conduction velocities of some vagal signals in the afferent (0.7-4.4 m/sec) and efferent (0.7-8.8 m/sec) directions, and monitored firing rate changes in breathing and blood glucose modulated conditions. Overall, these experiments demonstrated that CFMA is a novel interface for in-vivo intraneural action potential recordings. This work is considerable progress towards the comprehensive understanding of physiological neural signaling in vital regulatory functions controlled by autonomic nerves.

bioengineering↗