Inductively powered arbitrary-waveform adaptive-supply electro-optical neurostimulator

A hybrid current-mode and optogenetic miniature neurostimulating system is presented. The 16-channel electrical stimulator outputs arbitrary-waveform charge-balanced current-mode stimulation pulses with the amplitude ranging from 0.05mA to 10mA. To optimize power consumption, the supply voltage is automatically adjusted through an impedance monitoring feedback loop that gauges the minimum required headroom voltage. The 8-channel optogenetic stimulator reuses the arbitrary-waveform generation functions of the electrical stimulator. Each pulse-generator drives one LED with a maximum of 25mA. The LEDs are assembled within a custom-made 4×4 ECoG grid electrode array, which enables precise optical stimulation of neurons with a 300μm spatial resolution and simultaneous monitoring of the neural response by the ECoG electrode, at different distances of the stimulation site. The implantable system is a 3×2.5×1 cm³ stack of a receiver coil and two mini-boards. The power is received by a 32-layer flexible inductive coil and is regulated by the wireless communication board. The adaptive neurostimulator board boosts the regulated voltage up to the level set by the feedback loop with a maximum of 24V. The system also receives stimulation parameters wirelessly from the amplitude-shift-keyed power carrier. Both electrical and optogenetic stimulation results from chronic and acute in vivo rodent experiments are presented.