  Growing evidence suggests that phase-locked deep brain stimulation (DBS) can
effectively regulate abnormal brain connectivity in neurological and
psychiatric disorders. This letter therefore presents a low-power SoC with both
neural connectivity extraction and phase-locked DBS capabilities. A 16-channel
low-noise analog front-end (AFE) records local field potentials (LFPs) from
multiple brain regions with precise gain matching. A novel low-complexity phase
estimator and neural connectivity processor subsequently enable
energy-efficient, yet accurate measurement of the instantaneous phase and
cross-regional synchrony measures. Through flexible combination of neural
biomarkers such as phase synchrony and spectral energy, a four-channel
charge-balanced neurostimulator is triggered to treat various pathological
brain conditions. Fabricated in 65nm CMOS, the SoC occupies a silicon area of
2.24mm2 and consumes 60uW, achieving over 60% power saving in neural
connectivity extraction compared to the state-of-the-art. Extensive in-vivo
measurements demonstrate multi-channel LFP recording, real-time extraction of
phase and neural connectivity measures, and phase-locked stimulation in rats.
