Time Multiplexed Active Neural Probe with 1356 Parallel Recording Sites

Abstract

We present a high electrode density and high channel count CMOS (complementary metal-oxide-semiconductor) active neural probe containing 1344 neuron sized recording pixels (20 µm × 20 µm) and 12 reference pixels (20 µm × 80 µm), densely packed on a 50 µm thick, 100 µm wide, and 8 mm long shank. The active electrodes or pixels consist of dedicated in-situ circuits for signal source amplification, which are directly located under each electrode. The probe supports the simultaneous recording of all 1356 electrodes with sufficient signal to noise ratio for typical neuroscience applications. For enhanced performance, further noise reduction can be achieved while using half of the electrodes (678). Both of these numbers considerably surpass the state-of-the art active neural probes in both electrode count and number of recording channels. The measured input referred noise in the action potential band is 12.4 µVrms, while using 678 electrodes, with just 3 µW power dissipation per pixel and 45 µW per read-out channel (including data transmission).

Why not record from every electrode with a CMOS scanning probe?

“…The noise level for the 212 electrodes using the external reference (a screw in the animal's skull), with 2 groups and 12 groups powered, is 10.2 ± 0.1 μV and 12.0 ± 0.1 μV, respectively. This compares to the noise reported by (Raducanu et al, 2017) of 12.4 ± 0.9 μV for 6 groups on. In that work the noise for a 12 group recording is not reported but data are shown that describe how a full probe recording (12 groups) has a low enough noise to allow recordings from hundreds of neurons (results that we also corroborate here).…”

“…The NeuroSeeker project is the culmination of a number of efforts to translate major advances in microfabrication into new tools for electrophysiology (Neves et al, 2008b;Torfs et al, 2011;Lopez et al, 2013;Jun et al, 2017b;Raducanu et al, 2017;Herbawi et al, 2018;Dorigo et al, 2018;Seidl et al, 2011). The project has produced a device with multiplexing electrode scanning circuitry within the thin shaft of an implantable neural probe, which provides the highest number of simultaneous outputs for a single shaft in vivo extracellular recording device ever achieved.…”

“…Each session generated between 3.3M and 8M spikes per hour of recording. Spikes were represented on groups of adjacent electrodes that ranged in size between 10 and 50 with most of the spikes showing on at least 40 electrodes (for a more detailed description of a neuron's spread over the probe see (Raducanu et al, 2017)). We spike sorted some representative sessions to demonstrate the robustness of the recordings over time and our ability to remove the probe from one animal, implant it in another, and still get recordings of the same quality as a new probe, evidenced by the number of single units we could recover.…”

“…The NeuroSeeker European research project aimed to produce CMOS-based, time multiplexing, silicon probes for extracellular electrophysiological recordings with 1344 electrodes on a 50 µm thick, 100 µm wide, and 8 mm long shank with a 20 x 20 µm electrode size and a pitch of 22.5 µm (see Box 1 for a technical overview of the probe and (Raducanu et al, , 2017 for an in depth description of the probe's design). This innovative solution has allowed the neuroscientists within the consortium to record brain activity with an unprecedented combination of resolution and scale.…”

CHIME: CMOS-hosted in-vivo microelectrodes for massively scalable neuronal recordings

“…Apart from the individual electrodes, scaling has been frustrated by the engineering challenge for connectors, amplification and digitization. One approach to mitigate this has been to integrate electronics, multiplexing before connecting (Lopez et al, 2014;Raducanu et al, 2017;Fiáth et al, 2018), but integrating active electronics also requires a largely planar electrode architecture. A further limit to upscaling these approaches is that with further size reduction of individual electrodes, generally coupling impedance and signal loss increase.…”