A 3D microsystem for multi-site penetrating extracellular neural recording from the brain is presented. A 16 16-channel neural recording interface integrated prototype fabricated in 0.35 m CMOS occupies 3.5 mm 4.5 mm area. Each recording channel dissipates 15 W of power with input-referred noise of 7 V rms over 5 kHz bandwidth. A switched-capacitor delta read-out data compression circuit trades recording accuracy for the output data rate. An array of 1.5 mm platinum-coated microelectrodes is bonded directly onto the die. Results of in vitro experimental recordings from intact mouse hippocampus validate the circuit design and the on-chip electrode bonding technology.

We present a 320-channel active probe for high-spatial-resolution neuromonitoring and responsive neurostimulation. The probe comprises an integrated circuit (IC) cell array bonded to the back side of a pitch-matched microelectrode array. The IC enables up to 256-site neural recording and 64-site neural stimulation at the spatial resolution of 400 μ m and 200 μ m, respectively. It is suitable for direct integration with electrode arrays with the shank pitch of integer multiples of 200 μm. In the presented configuration, the IC is bonded with a 8 × 8 400 μ m-pitch Utah electrode array (UEA) and up to additional 192 recording channels are used for peripheral neuromonitoring. The 0.35 μ m CMOS circuit array has a total die size of 3.5 mm × 3.65 mm. Each stimulator channel employs a current memory for simultaneous multi-site neurostimulation, outputs 20 μA-250 μA square or arbitrary waveform current, occupies 0.02 mm (2), and dissipates 2.76 μ W quiescent power. Each fully differential recording channel has two stages of amplification and filtering and an 8-bit single-slope ADC, occupies 0.035 mm (2) , and consumes 51.9 μ W. The neural probe has been experimentally validated in epileptic seizure propagation studies in a mouse hippocampal slice in vitro and in responsive neurostimulation for seizure suppression in an acute epilepsy rat model in vivo .

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A low-power VLSI seizure detector is presented. It combines a 256-channel analog neural recording chip and a low-power synthesized digital VLSI processor. The processor computes the bivariate phase synchronization on any two neural inputs from a set of 256 and their instantaneous magnitude. For experimentation with in vitro epilepsy models, a low-cost technique to implement on-chip gold microelectrodes was utilized. Results are shown using an in vitro low Mg2+ mouse epilepsy model and human EEG data.

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