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Design and Verification of a Closed-loop-ready High-channel-count Neuromodulation Unit


According to a report by the World Health Organization (WHO), neuropsychiatric disorders affect about one billion people worldwide and are the leading cause of disability in the U.S.. To address this global epidemic, neuroscientific initiatives are being developed globally.

Deep brain stimulation (DBS) has been successful alternate treatment modality for some neuropsychiatric disorders (Parkinson’s disease, essential tremor, dystonia, and obsessive-compulsive disorder) when traditional treatment options failed (resection, medication, and psychotherapy). According to one long term study targeting Parkinson’s disease, patients’ motor function and daily activity-scores improve about 50% while off medication and receiving only DBS therapy. This therapy is delivered through large electrodes in the form of fixed-frequency rectangular stimulation pulses in an always-on, open-loop fashion - ignoring the disease state, medication status, or side effects.

In this work, we present a more advanced neural implant which, while being backward compatible with traditional DBS therapy, 1) is capable of sensing neural signals while delivering stimulation, 2) has high-channel-count, and 3) can generate non-rectangular stimulation waveforms. These key features are enabled by our custom-designed neural sensing and stimulation integrated circuits (ICs), which along with a few passive components, a miniature printed circuit board, and our user-friendly graphical interface comprise a capable neuromodulation system.

Our sensing IC’s ability to capture neural signals and stimulation artifacts without saturation at implant-level power is unique. Sampled local field potential (LFP) signals can be used to close the knowledge gap about the disease biomarkers and be fed into closed-loop algorithms for automatic tuning of stimulation parameters based on the disease state. The resulting autonomy will reduce or eliminate the need for periodic clinical visits for re-adjusting stimulation parameters to ameliorate neural network’s habituation effects.

Our high-channel-count stimulation IC, when paired with high-density probes, will substantially increase the spatial resolution of DBS, which can improve the therapeutic index and potentially result in lower power consumption for achieving the same therapeutic benefits. Also, the ability of our stimulation IC to generate custom, non-rectangular waveforms can lead to increased implant battery life, as some non-rectangular waveforms seem to be more energy efficient.

We believe that the proposed system has the potential to improve the quality of patient care and to further our understanding of neuropsychiatric disorders, and we hope that it will soon find an increased use in various clinical and research environments.

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