Neurochemostat: A Neural Interface SoC With Integrated Chemometrics for Closed-Loop Regulation of Brain Dopamine

Abstract

This paper presents a 3.3 × 3.2mm2 system-on-chip (SoC) fabricated in AMS 0.35µm 2P/4M CMOS for closed-loop regulation of brain dopamine. The SoC uniquely integrates neurochemical sensing, on-the-fly chemometrics, and feedback-controlled electrical stimulation to realize a “neurochemostat” by maintaining brain levels of electrically evoked dopamine between two user-set thresholds. The SoC incorporates a 90µW, custom-designed, digital signal processing (DSP) unit for real-time processing of neurochemical data obtained by 400V/s fast-scan cyclic voltammetry (FSCV) with a carbon-fiber microelectrode (CFM). Specifically, the DSP unit executes a chemometrics algorithm based upon principal component regression (PCR) to resolve in real time electrically evoked brain dopamine levels from pH change and CFM background-current drift, two common interferents encountered using FSCV with a CFM in vivo. Further, the DSP unit directly links the chemically resolved dopamine levels to the activation of the electrical microstimulator in on-off-keying (OOK) fashion. Measured results from benchtop testing, flow injection analysis (FIA), and biological experiments with an anesthetized rat are presented.

System on Chip for Closed Loop Neuromodulation Based on Dual Mode Biosignals

“…Hence, in this algorithm, a multivariate approach is adopted by using PCA. This is similar to the application of PCA on cyclic voltammetry curves described in [10], [11].…”

“…The different variables that are considered are pre-injection pH background, CCK-induced pH response and post-injection pH background. More details about the technique in[11].Bandpass filter ( 200 Hz -5 kHz) The system architecture of the CAP signal processor.…”

Platform for Closed Loop Neuromodulation Based on Dual Mode Biosignals

“…Hence, in this algorithm a multivariate approach is adopted by using Principal Component Analysis (PCA). This is similar to the application of PCA on cyclic voltammetry curves described in details in [12], [13].…”

A Bidirectional-Current CMOS Potentiostat for Fast-Scan Cyclic Voltammetry Detector Arrays

“…Fast-scan cyclic voltammetry (FSCV) has been used to perform such measurements on release events from different cell types [7], [16]. In FSCV at a CFM [17], [18], the electrode potential is typically ramped up and down within 10 ms, and these sweeps, or scans, are repeated every 100 ms. The fast rate at which the voltage changes, or the high scan rate, gives rise to a large background current on which the small faradaic current from the reduction and oxidation ( redox ) of an electroactive compound is superimposed [19].…”