Closed-Loop Neuromodulation System-on-Chip (SoC) for Detection and Treatment of Epilepsy

This chapter presents a 16-channel closed-loop neuromodulation system-on-chip (SoC) for detection and treatment on human epilepsy. In this SoC, a 16-channel neural-signal acquisition unit (NSAU), a biosignal processor (BSP), a 16-channel high-voltage-tolerant stimulator (HVTS), as well as wireless power and bidirectional data telemetry are included. In the NSAU, the input protection circuit is used to prevent MOSFET devices from electrical overstress during the high-voltage stimulations. Hence, NSAUs can share the same electrodes with stimulators. The auto-reset chopper-stabilized capacitive-coupled instrumentation amplifiers (AR-CSCCIAs) are designed with the chopper-stabilized technique with offset reduction loop. The entropy-and-spectrum seizure detection algorithm is implemented in the BSP, which can perform 0.76-s seizure detection latency and 97.8% detection accuracy in the experimental results. When the seizure onset is detected by the BSP, the HVTS with adaptive supply control can deliver biphasic current stimulation of 0.5 ~ 3 mA to suppress the seizure onset. The developed SoC is powered wirelessly, and the bidirectional data telemetry is realized through the same pair of coils in 13.56 MHz. The downlink data rate is 211 Kb/s with the binary phase-shift keying (BPSK) modulation and a BPSK demodulator. The uplink data rate is 106 Kb/s with the load-shift keying (LSK) modulation. The developed SoC has been fabricated in a 0.18-µm low-voltage CMOS process with 1.8 V/3.3 V devices. Electrical tests have been performed to characterize the SoC performance. In vivo animal experiments using minipigs have been performed to successfully verify the closed-loop neuromodulation functions on epileptic seizure suppression. In human clinical trials, the developed SoC has been performed to successfully suppress human epileptic seizures by closed-loop stimulation.