A Wireless Optogenetic Headstage with Multichannel Electrophysiological Recording Capability

Abstract

We present a small and lightweight fully wireless optogenetic headstage capable of optical neural stimulation and electrophysiological recording. The headstage is suitable for conducting experiments with small transgenic rodents, and features two implantable fiber-coupled light-emitting diode (LED) and two electrophysiological recording channels. This system is powered by a small lithium-ion battery and is entirely built using low-cost commercial off-the-shelf components for better flexibility, reduced development time and lower cost. Light stimulation uses customizable stimulation patterns of varying frequency and duty cycle. The optical power that is sourced from the LED is delivered to target light-sensitive neurons using implantable optical fibers, which provide a measured optical power density of 70 mW/mm2 at the tip. The headstage is using a novel foldable rigid-flex printed circuit board design, which results into a lightweight and compact device. Recording experiments performed in the cerebral cortex of transgenic ChR2 mice under anesthetized conditions show that the proposed headstage can trigger neuronal activity using optical stimulation, while recording microvolt amplitude electrophysiological signals.

A novel wireless ring-shaped multi-site pulse oximeter

“…In addition, a passive power supply filter network is designed to be located after the regulation circuitry to remove the optical fluctuation effects. This passive network has a low-pass behavior and compensates the low PSRR of the LDO voltage regulator at higher frequencies [63].…”

A Wireless Headstage for Combined Optogenetics and Multichannel Electrophysiological Recording

“…We are introducing the first wireless headstage system entirely built using commercial components that process and transmit 32 neural data acquisition channels in parallel in addition to controlling 32 implantable fiber-coupled optical stimulation LEDs. Compared to an early version reported by our group in [18], the proposed headstage includes 32/32 recording/stimulation channels instead of 2/2, and is using an action potential detector and a neural signal compression module implemented inside a low-power digital signal processor, while being smaller and lighter than [18] (2.8 g versus 4.9 g). A major contribution of this work is that the filters, memories, clock speeds required for spike detection and wavelet compression have been implemented on a lowpower field programmable gate array (FPGA) in a practical and feasible manner.…”

“…Likewise, the commercial wireless systems, such as [8] and [9], either provide multichannel neural recording (up to 126 channels) or optical stimulation from a maximum of 2 channels, but not both functions simultaneously within a single system. Besides, the COTS based system presented in [18] weighs 4.9 g and provides both functions, but is limited to 2 high-power optical stimulation channels and 2 electrophysiological recording channels.…”

A multi-site MicroLED Optrode Array for Neural Interfacing

“…Light is normally coupled to the cannula using a fibre optic, where the resultant tethering can restrict animal movement, affecting behaviour. However, options are becoming available that couple an LED directly to the cannula and allow for more natural animal movement [10]. This type of device is suitable for non-human primate studies where only a single excitation source is required.…”

“…The device is capable of peak irradiances > 80 mW/mm 2 per needle at 50 ms pulse widths with a maximum repetition rate of 1.2 Hz (to limit tissue temperature increases to less than 1 °C). Furthermore, the integration of the light sources and UOA opens up the option of a fully wireless compact device [10,15]. The fabricated device is a 10 x 10 array of glass needles, each measuring 1.5 mm in length and spaced at 400-micron pitch ( Fig.…”