(44) Novel Approach for Enhancing Signal Recovery During Stimulation

Introduction: Deep brain stimulation (DBS) is a neuromodulation-based therapy that consists in delivering electrical stimulation within targeted brain regions for therapeutic benefit. DBS local evoked potentials (DLEPs) are a novel marker evoked by stimulation, characterized by short (~10-25ms), damped oscillations. There has been an increased interest in leveraging DLEPs to inform surgical targeting and for the optimization of DBS programming. However, recovering this marker from stimulated contacts is inherently challenging due to large stimulation artifacts and amplifier-saturation. This is exacerbated by the limited spatial sampling offered by current DBS electrode configurations (low number of contacts). Thus, there is a need for improved methods to enhance signal recovery of short latency activity evoked by stimulation. This work introduces and expands upon a novel system, Fully Passive Clipping for Recovering Electrophysiology (FPClipre)1, designed to mitigate limitations in current recording and stimulating systems without the addition of active components that require more challenging control.

Methods: FPClipre achieves this improved signal recovery through 3 stages, the “current limiter stage,” “voltage range limiter stage,” and “stimulation decoupler stage,” to effectively reduce stimulation artifacts while enabling recovery of viable electrophysiology from the same and adjacent contacts post-stimulation (after each stimulation pulse). This was tested in vitro by delivering a cathodic current stimulation burst (1mA asymmetric 100μs-0μs-833μs) at 130Hz through an Abbott/St. Jude Directed DBS lead immersed into a saline bath. The impedance at each contact was ~4kΩ. We simulated underlying parkinsonian beta oscillatory activity by injecting a 20Hz (beta) sine wave, together with a simulated DLEPs wave directly after each stimulation burst. Signals were recovered on a Tucker-Davis Technologies (TDT) Lab Rat recording amplifier both with and without FPClipre.

Results: Pilot data from in vitro testing have shown that FPClipre can recover and maintain signal fidelity with minimal distortion ( < 0.2%) and avoid any current sinking effect towards the recording amplifier (current loss below 2µA). Importantly, using FPClipre we demonstrated signal recovery directly from the stimulating contact. The passive nature of the FPClipre approach simplifies the integration into existing stimulation-based setups. Additionally, this method is not limited to DBS and can be leveraged within any setup requiring recording during stimulation.

Conclusion: The proposed system has the strong potential to remove current limitations in neuromodulation research and clinical applications setups by enhancing recovery of pathophysiological and spatial markers directly influenced by stimulation. Further in vivo testing in preclinical models is necessary before the implementation in human studies.