A Wireless Headstage for Combined Optogenetics and Multichannel Electrophysiological Recording

Abstract

This paper presents a wireless headstage with real-time spike detection and data compression for combined optogenetics and multichannel electrophysiological recording. The proposed headstage, which is intended to perform both optical stimulation and electrophysiological recordings simultaneously in freely moving transgenic rodents, is entirely built with commercial off-the-shelf components, and includes 32 recording channels and 32 optical stimulation channels. It can detect, compress and transmit full action potential waveforms over 32 channels in parallel and in real time using an embedded digital signal processor based on a low-power field programmable gate array and a Microblaze microprocessor softcore. Such a processor implements a complete digital spike detector featuring a novel adaptive threshold based on a Sigma-delta control loop, and a wavelet data compression module using a new dynamic coefficient re-quantization technique achieving large compression ratios with higher signal quality. Simultaneous optical stimulation and recording have been performed in-vivo using an optrode featuring 8 microelectrodes and 1 implantable fiber coupled to a 465-nm LED, in the somatosensory cortex and the Hippocampus of a transgenic mouse expressing ChannelRhodospin (Thy1::ChR2-YFP line 4) under anesthetized conditions. Experimental results show that the proposed headstage can trigger neuron activity while collecting, detecting and compressing single cell microvolt amplitude activity from multiple channels in parallel while achieving overall compression ratios above 500. This is the first reported high-channel count wireless optogenetic device providing simultaneous optical stimulation and recording. Measured characteristics show that the proposed headstage can achieve up to 100% of true positive detection rate for signal-to-noise ratio (SNR) down to 15 dB, while achieving up to 97.28% at SNR as low as 5 dB. The implemented prototype features a lifespan of up to 105 minutes, and uses a lightweight (2.8 g) and compact [Formula: see text] rigid-flex printed circuit board.

The Neural Engine: A Reprogrammable Low Power Platform for Closed-Loop Optogenetics

“…Therefore, translating these devices into clinical applications would require further power optimization efforts to avoid battery life and thermal issues. Meanwhile, [10] and our own effort employ optogenetic based stimulations [33], while the others use traditional electrical stimulation, which cannot be genetically targetted [34]. Regarding freely moving experiments, our system also shows both primates/rodents reliable LFP recordings.…”

“…However, the overall consumption was significantly large at 284mW. Similarly, Gagnon-Turcotte et al demonstrated a strong computing scalability system with 32 recording/stimulation channels with a comprehensive wavelet data compression technique [10]. The power consumption is still relatively high at 119mW.…”

“…An alternative to having fixed algorithms in silicon is to configure multiple independent filters which can be called in sequence or utilize reconfigurable digital logic. Gagnon-Turcotte et al [10] utilized option (ii), and developed a wireless headset for high resolution 32-channel electrical recording in tandem with optical stimulations. Their system utilized a lowpower FPGA based DSP for a digital spike detector and a wavelet data compression module.…”

Hearing restoration by a low-weight power-efficient multichannel optogenetic cochlear implant system

“…Future modifications of the described hard-and software framework will also accommodate the combination of electrical and optical stimulation (combined oCI and eCI) for hybrid electro-optical stimulation 26 or optofluidics circuitry for application of photopharmacology into the cochlea and later optical stimulation [67][68][69] . Most studies presenting optogenetic stimulators address brain stimulation [70][71][72][73] , e.g. cortical control of movement 74 , and also peripheral nervous system 75 .…”

Telemetry-controlled simultaneous stimulation-and-recording device (SRD) to study interhemispheric cortical circuits in rat primary somatosensory (SI) cortex

“…Existing systems used in research are capable of wirelessly transmitting recorded neural signals [2,4,19,20] and wirelessly controlling stimulation [21], but some systems are limited by the use of noncommercial ASIC designs [2,4,21,22] or do not provide on-board synchronized recording with external stimuli [5,23,24] but this is not without exception [21]. Devices capable of simultaneous surface electrical or optical stimulation and recording have also been developed with low-power consumption and high noise immunity [22,25,26].…”