A Neurochemical Pattern Generator SoC With Switched-Electrode Management for Single-Chip Electrical Stimulation and 9.3 µW, 78 pA rms , 400 V/s FSCV Sensing

This paper describes a system-on-chip (SoC) fabricated in AMS 0.35 μm 2P/4M CMOS for high-fidelity neurochemical pattern generation in vivo. The SoC uniquely integrates electrical stimulation with embedded timing management for generation of neurochemical patterns and 400 V/s fast-scan cyclic voltammetry (FSCV) sensing for subsequent assessment of fidelity in the generated profiles, and manages a novel switched-electrode scheme that eliminates the possibility of large stimulus artifacts adversely affecting electrochemistry. The SoC also leverages the discontinuous sampling inherent in FSCV to reduce the sensing power consumption by 87.5% to 9.3 μW from 2.5 V using a duty-cycled, 3rd-order, continuous-time, ΔΣ modulator (CT-ΔΣM) with an input-referred noise current of 78 pA_rms (dc - 5 kHz) within an input current range of ±950 nA. Utilizing a transfer function that relates electrical stimulation of dopamine axons traversing the medial forebrain bundle (MFB) to evoked extracellular dopamine dynamics in the dorsal striatum of the forebrain, the correlation coefficient between predicted and measured dopamine temporal profiles was found to be 0.95 in an anesthetized rat.