Shin, Hojin

Understanding the complex interplay between electrical activity and neurochemical signaling is essential for advancing neuromodulation therapies, yet current technologies often measure these modalities in isolation and suffer from technical limitations such as stimulation artifacts. To address these challenges, we developed the Multifunctional Apparatus for Voltammetry, Electrophysiology, and Neuromodulation (MAVEN), a compact, battery-powered platform designed for high-resolution, concurrent multimodal data acquisition. Preclinical validation in both small- and large-animal models demonstrated that MAVEN provides stable, high-fidelity multimodal readouts while effectively minimizing stimulation artifacts during simultaneous programmable neurostimulation. By capturing phasic and tonic neurochemical changes, alongside real-time electrophysiological data, we established the system's feasibility for continuous monitoring. Beyond its utility in investigating the mechanisms of neurological and neuropsychiatric disorders, MAVEN has been engineered as a versatile analytical platform. Recent successful applications in monitoring pharmacological agents, such as vancomycin, further demonstrate its potential as a robust point-of-care device for real-time diagnostic and therapeutic monitoring. These results position MAVEN not only as a powerful tool for developing personalized, closed-loop neuromodulation strategies but also as a next-generation analytical device capable of broader clinical and bio-sensing applications.

Abstract Objective. Modern stereotactic neurosurgery increasingly relies on bilateral and multi-trajectory workflows (e.g. deep brain stimulation (DBS), stereoelectroencephalography (sEEG)), which can exceed the reach and flexibility of conventional frame-based systems. Building on our skull-mounted Navinetics D1 platform, we present a stereotactic frame (Navinetics E1) intended to expand the reachable work envelope, enable independent bilateral targeting, and preserve mechanical accuracy and patient comfort. Approach. We designed the Navinetics E1 stereotactic frame using a center-of-arc architecture with five degrees of freedom per hemisphere ( X, Y, Z , Arc, Collar) and two operating modes: Double Arm (independent left/right arms for simultaneous bilateral targeting) and Single Arm (mechanically coupled arms). The system was designed in CAD and fabricated via carbon fiber-reinforced polylactic acid (PLA-CF) additive manufacturing. Collision-aware MATLAB simulations quantified work volume and admissible approach directions. Mechanical targeting accuracy was evaluated on a ground truth fixture (GTF) platform, with mixed-effects modeling to assess target- and trajectory-dependent effects. Operative feasibility was assessed through an intraoperative entry-point replication test relative to the D1 system. Main results. Compared to the D1, the E1 frame significantly expanded key geometric ranges, including, most notably, 0°–360° Collar rotation and posterior Y -axis reach, thereby increasing the work volume and trajectory range by factors of 3.39 and 8.42, respectively. Mean GTF targeting deviation was 0.78 ± 0.38 mm in Single Arm mode and 1.23 ± 0.36 mm (right) and 1.65 ± 0.47 mm (left) in Double Arm mode. Entry-point replication across 17 clinical cases achieved 76.5% success in overlapping the reference points, providing preliminary evidence of feasibility under real operative conditions. Significance. The E1 frame extends a compact skull-mounted platform to support broader stereotactic reach and trajectory while enabling independent bilateral workflows. These features may reduce intraoperative reconfiguration for complex DBS and sEEG cases. Future work will focus on increasing structural stiffness, improving angular readout/setting, and developing MRI-compatible implementations.

ABSTRACT Real time, chronic electrochemical detection of neurotransmitters will provide a positive step in the treatment and understanding of neurological disease. However, current electrodes using carbon fibers (CF) fail to perform chronically. While diamond‐based coatings show promise in improving their longevity, achieving a uniform layer of such coatings on CFs is challenging, and the electrodes often lose sensitivity after coating. In this work, a complete and uniform boron‐doped nanocrystalline material grown in a diamond reactor (B‐NCD) was developed to coat CF microelectrodes for neurochemical sensing. The coating was characterized electrically, optically, mechanically, and chemically. The B‐NCD coated CF electrodes were able to detect phasic dopamine at a sensitivity comparable to the most widely used alternatives (uncoated and PEDOT:Nafion coated CFs). During biofouling testing, the B‐NCD coated CF electrodes demonstrated better stability than uncoated CFs and comparable performance to PEDOT:Nafion coated CFs. Moreover, B‐NCD exhibited no signs of degradation during consecutive FSCV applications, while uncoated and PEDOT:Nafion coated CF electrodes degraded significantly over time. Furthermore, the B‐NCD coating supported the survival and development of neurons and astrocytes in vitro, exhibited excellent adhesion and durability during mechanical bending testing, and enabled successful in vivo recording of phasic dopamine release in the rat brain. Overall, B‐NCD coated CFs present as an ideal candidate for chronic, flexible neural implantable electrodes for long‐term neurochemical monitoring.

OBJECTIVE Achieving submillimetric accuracy in stereotactic neurosurgery remains critical for safely targeting deep brain structures. Current workflows rely on intraoperative CT to register stereotactic frames to preoperative imaging, but this introduces additional radiation exposure, cost, and workflow complexity. Three-dimensional surface scanning (3DSS) potentially offers a fast radiation-free alternative capable of capturing detailed craniofacial anatomy and frame geometry. Therefore, the aim of this cadaveric study was to evaluate the feasibility, accuracy, and navigational compatibility of integrating 3DSS into stereotactic workflows as a potential replacement for intraoperative CT. METHODS A human cadaveric head was imaged with both thin-slice CT and structured-light 3DSS after mounting stereotactic frame components. CT, 3DSS, and computer-aided design (CAD) models were registered using a multistep point cloud alignment pipeline involving the fast point feature histogram, the random sample consensus method, and the iterative closest point algorithm. Accuracy was assessed using surface deviation error, root mean square error (RMSE), and fiducial registration error within a commercial neuronavigation platform. RESULTS Fusion of the 3D facial scan with CT provided a mean surface deviation error of approximately 0.4 mm. Registration of the 3DSS-derived N-bar localizer to its CAD reference model produced a frame alignment RMSE of 1.3 mm. Within the navigation system, the 3DSS-based workflow achieved a mean fiducial registration error of 0.14 mm (range 0.02–0.20 mm), outperforming the conventional CT-based method (mean error 0.20 mm, range 0.09–0.40 mm). CONCLUSIONS The 3DSS-based method enabled precise submillimetric stereotactic registration without the need for intraoperative CT, reducing radiation exposure and operative complexity. This workflow is fully compatible with existing navigation systems and could serve as a practical radiation-free alternative in stereotactic neurosurgery. Future work will focus on automating frame detection, incorporating artificial intelligence–driven fusion methods, and validating this approach in live surgical settings.

Background: Invasive and non-invasive neuromodulation in psychiatry represents a burgeoning field that leverages advanced neuromodulation techniques to address substance use disorders (SUDs). Aims: This narrative review synthesizes findings from multiple reviews to evaluate the efficacy of neuromodulation in treating SUDs. Methods: A comprehensive literature search was conducted between December 2024 and April 2025, focusing on systematic reviews and meta-analyses that examined various neuromodulation modalities, including repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS), and deep brain stimulation (DBS). The selected reviews were analyzed to identify common themes, outcomes, and gaps in the current understanding of these treatments for SUDs. Results: 11 reviews met the final inclusion criteria; 5 focused on non-invasive neuromodulation (rTMS, tDCS) and 6 on invasive neuromodulation (DBS). Non-invasive neurostimulation was associated with modest improvements in craving and cognitive dysfunction in individuals with SUDs. Similarly, invasive neuromodulation (DBS), through high-frequency stimulation of the bilateral nucleus accumbens, appeared to reduce cravings and improve comorbid psychiatric symptoms in both preclinical and human studies. Importantly, small sample sizes, heterogeneity in targets and stimulation protocols, and short follow-up periods significantly limit the generalizability of current findings from both non-invasive and invasive neuromodulation studies. Conclusions: As novel and more effective therapies for the treatment of SUD are desperately needed, procedural interventional psychiatry holds promise. However, despite encouraging results, existing evidence is still preliminary, and larger, rigorously designed studies are warranted to further establish the safety and efficacy of neuromodulatory interventions for SUD treatment.

Abstract Introduction: Opioid use disorder constitutes a significant health crisis in the United States, contributing to high rates of opioid overdose-related deaths. A major driver of these fatalities is fentanyl, a potent synthetic opioid with both sedative and analgesic properties. These properties that make fentanyl clinically effective also increase its addictive potential. Early in opioid addiction, abnormal increases in extracellular dopamine in the nucleus accumbens (NAc) reinforce excessive drug-seeking behaviors which can lead to fatal respiratory depression. Given this mechanism, we investigated whether high frequency stimulation (HFS), mimicking human deep brain stimulation (DBS) of the ventral tegmental area (VTA) could block NAc dopamine increase following an acute lethal dose of fentanyl. We hypothesized that VTA DBS would mitigate these dopaminergic responses and prevent fentanyl-induced respiratory failure. Methods: Multiple cyclic square wave voltammetry (M-CSWV), was applied via a carbon fiber microelectrode in the NAc of urethane-anesthetized male Sprague-Dawley rats. Dopamine levels were recorded at baseline and following acute fentanyl (30 µg/kg, i.v.). HFS (130 Hz frequency, 200 µsec pulse width, and 0.2 mA amplitude) was administered to the VTA before and during fentanyl exposure. Results: Acute fentanyl administration resulted in a 178.2% increase in NAc dopamine levels from baseline, accompanied by a decline in respiratory rates to critically low levels (45 breaths per minute vs. 102 bpm), eventually resulting in 100% mortality. HFS of the VTA did not significantly alter baseline tonic dopamine levels or prevent fentanyl-induced dopamine increase in the NAc but was able to fully rescue fentanyl-induced respiratory failure.

BACKGROUND AND OBJECTIVES: A typical workflow for deep brain stimulation (DBS) surgery consists of head frame placement, followed by stereotactic computed tomography (CT) or MRI before surgical implantation of the hardware. At some institutions, this workflow is prolonged when the imaging scanner is located far away from the operating room, thereby increasing workflow times by the addition of transport times. Recently, the intraoperative O-arm has been shown to provide accurate image fusion with preoperative CT or MR imaging, suggesting the possibility of obtaining an intraoperative localization scan and postoperative confirmation. In this article, we aim to evaluate the compatibility of the stereotactic frame system with the intraoperative O-arm system regarding lead accuracy and surgical flow. METHODS: A total of 17 patients undergoing DBS surgery for movement disorders were evaluated. One patient underwent both the stereotactic CT and O-arm localization, while 16 patients underwent only intraoperative O-arm localization. Following lead placement, intraoperative O-arm imaging was obtained to evaluate the accuracy of the lead placement. Accuracy was defined as the error measured as the distance from the center of the planned trajectory to the cannula. RESULTS: Less than 0.1 mm difference was found between the O-arm imaging technique and CT image localization of the NaviNetics stereotactic head frame in DBS surgery. Of the 16 patients who underwent the intraoperative O-arm imaging alone, the targets included bilateral ventral intermediate nucleus (16 leads), bilateral globus pallidus internus (4 leads), and subthalamic nucleus (12 leads). The mean ± SD radial error in the probe's eye view was 0.71 ± 0.33 mm for n = 32 leads. No tract hemorrhage was observed. CONCLUSION: Intraoperative O-arm imaging can be used safely and effectively for stereotactic registration and lead placement confirmation with the stereotactic system in both awake and asleep DBS surgery.