Verification of a Rapidly Multiplexed Circuit for Scalable Action Potential Recording.

Mohit Sharma,Ross Martin Walker,Hunter Joseph Strathman

doi:10.1109/tbcas.2019.2958348

Mohit Sharma, Ross Martin Walker + Show 1 more

Open Access

https://doi.org/10.1109/tbcas.2019.2958348

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Abstract

This report presents characterizations of in vivo neural recordings performed with a CMOS multichannel neural recording chip that uses rapid multiplexing directly at the electrodes, without any pre-amplification or buffering. Neural recordings were taken from a 16-channel microwire array implanted in rodent cortex, with comparison to a gold-standard commercial bench-top recording system. We were able to record well-isolated threshold crossings from 10 multiplexed electrodes and typical local field potential waveforms from 16, with strong agreement with the standard system (average SNR = 2.59 and 3.07 respectively). For 10 electrodes, the circuit achieves an effective area per channel of 0.0077 mm2, which is >5x smaller than typical multichannel chips. Extensive characterizations of noise and signal quality are presented and compared to fundamental theory, as well as results from in vivo and in vitro experiments. By demonstrating the validation of rapid multiplexing directly at the electrodes, this report confirms it as a promising approach for reducing circuit area in massively-multichannel neural recording systems, which is crucial for scaling recording site density and achieving large-scale sensing of brain activity with high spatiotemporal resolution.

Highlights

E LECTROPHYSIOLOGICAL recording is the gold standard for measuring neural activity due to its potential for high spatiotemporal resolution [1]
The measured crosstalk depended on the clock duty cycle, since the settling on CS and the reset on CIN,adc happens during the narrow settling phase of the clock
The isolation method used was deemed appropriate since the main purpose of this study was to verify that rapid multiplexing directly at the electrodes can record the same events as traditional architectures

Summary

Introduction

E LECTROPHYSIOLOGICAL recording is the gold standard for measuring neural activity due to its potential for high spatiotemporal resolution [1]. Extracellular electrical recordings are typically made with multichannel electrode arrays implanted in brain tissue. The number of recorded neurons has steadily increased as electrode technology has improved over time [2]. The number of available neurons is still many orders of magnitude smaller than the total number of neurons in the brain. Large efforts are underway to increase the number of implanted electrodes, in order to provide a more complete picture of neural activity.

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