A Wireless Electro-Optic Headstage with Digital Signal Processing and Data Compression for Multimodal Electrophysiology and Optogenetic Stimulation

This paper presents a wireless electro-optic headstage for parallel electrophysiological recording of neural action potential (AP), local field potentials (LFP) and electromyography (EMG), while performing multichannel optical stimulation. The headstage is designed for enabling experiments with freely moving rodents, like small laboratory mice. It can record electrophysiological activity on up to 32 channels and stimulate with up to 4 optical channels using only commercial off the shelf (COTS) components. An embedded digital field-programmable gate array (FPGA) is used to allow real time digital separation of AP and LFP waveform and the recording of EMG. It also performs data reduction through AP detection and compression allowing to collect and transmit data wirelessly from 32 parallel channels. The digital filters are optimized to reduce latency so the 32 channels can be time multiplexed on a single data path to decrease power consumption and optimize resource utilisation. Performing signal separation allows the compression of the AP and the decimation of the LFP/EMG. This reduces the amount of data to transmit by a factor of 7.77 (for a firing rate of 50 AP/second) and allow a higher channel count for both signals. The headstage only weights 3.8 g w/ a 100 mAh battery and 4.68 g with the plastic packaging and on/off switch.