Abstract
This paper presents the design and the utilization of a wireless electro-optic platform to perform simultaneous multimodal electrophysiological recordings and optogenetic stimulation in freely moving rodents. The developed system can capture neural action potentials (AP), local field potentials (LFP) and electromyography (EMG) signals with up to 32 channels in parallel while providing four optical stimulation channels. The platform is using commercial off-the-shelf components (COTS) and a low-power digital field-programmable gate array (FPGA), to perform digital signal processing to digitally separate in real time the AP, LFP and EMG while performing signal detection and compression for mitigating wireless bandwidth and power consumption limitations. The different signal modalities collected on the 32 channels are time-multiplexed into a single data stream to decrease power consumption and optimize resource utilization. The data reduction strategy is based on signal processing and real-time data compression. Digital filtering, signal detection, and wavelet data compression are used inside the platform to separate the different electrophysiological signal modalities, namely the local field potentials (1–500 Hz), EMG (30–500 Hz), and the action potentials (300–5,000 Hz) and perform data reduction before transmitting the data. The platform achieves a measured data reduction ratio of 7.77 (for a firing rate of 50 AP/second) and weights 4.7 g with a 100-mAh battery, an on/off switch and a protective plastic enclosure. To validate the performance of the platform, we measured distinct electrophysiology signals and performed optogenetics stimulation in vivo in freely moving rondents. We recorded AP and LFP signals with the platform using a 16-microelectrode array implanted in the primary motor cortex of a Long Evans rat, both in anesthetized and freely moving conditions. EMG responses to optogenetic Channelrhodopsin-2 induced activation of motor cortex via optical fiber were also recorded in freely moving rodents.
Highlights
New tools to study the brain microcircuits of laboratory animals are highly sought after to advance our knowledge of the brain physiology and pathology
Synthetic Recording Results To validate whether the system can effectively record and separate action potentials (AP), local field potentials (LFP), and EMG signals simultaneously in real time, the EMG, AP and LFP signals recorded in the brain of a mouse in the course of previous in vivo experiments were played at the inputs of the platform using a Tektronix AFG 3101 arbitrary waveform generator
A Principal component analysis (PCA) has been performed on the resulting extracted APs for each channel and followed by a clustering task using the Kmeans algorithm to identify and sort the different AP shapes collected over each electrode, which result from different neurons
Summary
New tools to study the brain microcircuits of laboratory animals are highly sought after to advance our knowledge of the brain physiology and pathology. The development of reliable brain machine interfaces often require to perform parallel recording and stimulation in the motor cortex or other brain structures, while monitoring the EMG signals in muscles (Jackson et al, 2006; Ethier and Miller, 2015). The amplitudes and frequency bands of AP, LFP, and EMG, respectively range from 300 to 5,000 Hz and 50 to 500 μV (Liu et al, 2013), 1 to 500 Hz and 250 to 5,000 μV (Soltani et al, 2019), and 10 to 300 Hz and 50 to 500 μV (Soltani et al, 2019) Capturing all these waveforms concurrently requires a dedicated strategy. Data reduction and/or data compression strategies have proven essential to increase the channel count and resolution, while decreasing the size and the power consumption of such resources constrained devices
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
