Effects of Unilateral High Frequency Stimulation of the Subthalamic Nucleus on Risk-avoidant Behavior in a Partial 6-hydroxydopamine Model of Parkinson's Disease.

BACKGROUND: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is a well-established treatment for the motor symptoms of Parkinson's disease (PD). While PD is primarily characterized by motor symptoms such as tremor, rigidity, and bradykinesia, it also involves a range of non-motor symptoms, and anxiety is one of the most common. The relationship between PD and anxiety is complex and can be a result of both pathological neural changes and the psychological and emotional impacts of living with a chronic progressive condition. Managing anxiety in PD is critical for improving the patients' quality of life. However, patients undergoing STN DBS can occasionally experience increased anxiety. METHODS: This study investigates changes in risk-avoidant behavior following STN DBS in a pre-motor animal model of PD under chronic and acute unilateral high frequency stimulation. RESULTS: No significant changes in risk-avoidant behaviors were observed in rats who underwent STN DBS compared with sham stimulation controls. Chronic stimulation prevented sensitization in the elevated zero maze. CONCLUSIONS: These results suggest that unilateral stimulation of the STN may have minimal effects on risk-avoidant behaviors in PD. However, additional research is required to fully understand the mechanisms responsible for changes in anxiety during STN DBS for PD.

Midbrain dopaminergic degeneration differentially modulates primary motor cortex activity and motor behavior in hemi-parkinsonian rats.

Parkinson's disease (PD) is marked by degeneration in the nigrostriatal dopaminergic pathway, affecting motor control via complex changes in the cortico-basal ganglia-thalamic motor network, including the primary motor cortex (M1). The modulation of M1 neuronal activity by dopaminergic inputs, particularly from the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc), plays a crucial role in PD pathophysiology. This study investigates how nigrostriatal dopaminergic degeneration influences M1 neuronal activity in rats using in vivo calcium imaging. Histological analysis confirmed dopaminergic lesion severity, with high lesion level rats showing significant motor deficits. Levodopa treatment improved fine motor abilities, particularly in high lesion level rats. Analysis of M1 calcium signals based on dopaminergic lesion severity revealed distinct M1 activity patterns. Animals with low dopaminergic lesion showed increased calcium events, while high lesion level rats exhibited decreased activity, partially restored by levodopa. These findings suggest that M1 activity is more sensitive to transient fluctuations in dopaminergic transmission, rather than to chronic high or low dopaminergic signaling. This study underscores the complex interplay between dopaminergic signaling and M1 neuronal activity in PD symptoms development. Further research integrating behavioral and calcium imaging data can elucidate mechanisms underlying motor deficits and therapeutic responses in PD.

The role of spinal cord neuroanatomy and the variances of epidurally evoked spinal responses.

BACKGROUND: Spinal cord stimulation (SCS) has demonstrated multiple benefits in treating chronic pain and other clinical disorders related to sensorimotor dysfunctions. However, the underlying mechanisms are still not fully understood, including how electrode placement in relation to the spinal cord neuroanatomy influences epidural spinal recordings (ESRs). To characterize this relationship, this study utilized stimulation applied at various anatomical sections of the spinal column, including at levels of the intervertebral disc and regions correlating to the dorsal root entry zone. METHOD: Two electrode arrays were surgically implanted into the dorsal epidural space of the swine. The stimulation leads were positioned such that the caudal-most electrode contact was at the level of a thoracic intervertebral segment. Intraoperative cone beam computed tomography (CBCT) images were utilized to precisely determine the location of the epidural leads relative to the spinal column. High-resolution microCT imaging and 3D-model reconstructions of the explanted spinal cord illustrated precise positioning and dimensions of the epidural leads in relation to the surrounding neuroanatomy, including the spinal rootlets of the dorsal and ventral columns of the spinal cord. In a separate swine cohort, implanted epidural leads were used for SCS and recording evoked ESRs. RESULTS: Reconstructed 3D-models of the swine spinal cord with epidural lead implants demonstrated considerable distinctions in the dimensions of a single electrode contact on a standard industry epidural stimulation lead compared to dorsal rootlets at the dorsal root entry zone (DREZ). At the intervertebral segment, it was observed that a single electrode contact may cover 20-25% of the DREZ if positioned laterally. Electrode contacts were estimated to be ~0.75 mm from the margins of the DREZ when placed at the midline. Furthermore, ventral rootlets were observed to travel in proximity and parallel to dorsal rootlets at this level prior to separation into their respective sides of the spinal cord. Cathodic stimulation at the level of the intervertebral disc, compared to an 'off-disc' stimulation (7 mm rostral), demonstrated considerable variations in the features of recorded ESRs, such as amplitude and shape, and evoked unintended motor activation at lower stimulation thresholds. This substantial change may be due to the influence of nearby ventral roots. To further illustrate the influence of rootlet activation vs. dorsal column activation, the stimulation lead was displaced laterally at ~2.88 mm from the midline, resulting in variances in both evoked compound action potential (ECAP) components and electromyography (EMG) components in ESRs at lower stimulation thresholds. CONCLUSION: The results of this study suggest that the ECAP and EMG components of recorded ESRs can vary depending on small differences in the location of the stimulating electrodes within the spinal anatomy, such as at the level of the intervertebral segment. Furthermore, the effects of sub-centimeter lateral displacement of the stimulation lead from the midline, leading to significant changes in electrophysiological metrics. The results of this pilot study reveal the importance of the small displacement of the electrodes that can cause significant changes to evoked responses SCS. These results may provide further valuable insights into the underlying mechanisms and assist in optimizing future SCS-related applications.

Axonal pathways linked to therapeutic and nontherapeutic outcomes during psychiatric deep brain stimulation.

OBJECTIVE: The underlying hypothesis of our work is that specific clinical neuropsychiatric benefits can be achieved by selective activation of specific axonal pathways during deep brain stimulation (DBS). As such, the goal of this study was to develop a method for identifying axonal pathways whose activation is most likely necessary for achieving therapeutic benefits during DBS. EXPERIMENTAL DESIGN: Our approach combined clinical data, diffusion tensor tractography, and computer models of patient-specific neurostimulation to identify particular axonal pathways activated by DBS and determine their correlations with individual clinical outcome measures. We used this method to evaluate a cohort of seven treatment-resistant depression patients treated with DBS of the ventral anterior internal capsule and ventral striatum (VC/VS). PRINCIPAL OBSERVATIONS: Clinical responders exhibited five axonal pathways that were consistently activated by DBS. All five pathways coursed lateral and medial to the VS or dorsal and lateral to the nucleus accumbens; however, details of their specific trajectories differed. Similarly, one common pathway was identified across nonresponders. CONCLUSIONS: Our method and preliminary results provide important background for studies aiming to expand scientific characterization of neural circuitry associated with specific psychiatric outcomes from DBS. Furthermore, identification of pathways linked to therapeutic benefit provides opportunities to improve clinical selection of surgical targets and stimulation settings for DBS devices.

Integral methods for automatic quantification of fast-scan-cyclic-voltammetry detected neurotransmitters.

Modern techniques for estimating basal levels of electroactive neurotransmitters rely on the measurement of oxidative charges. This requires time integration of oxidation currents at certain intervals. Unfortunately, the selection of integration intervals relies on ad-hoc visual identification of peaks on the oxidation currents, which introduces sources of error and precludes the development of automated procedures necessary for analysis and quantification of neurotransmitter levels in large data sets. In an effort to improve charge quantification techniques, here we present novel methods for automatic selection of integration boundaries. Our results show that these methods allow quantification of oxidation reactions both in vitro and in vivo and of multiple analytes in vitro.

Defining a Path Toward the Use of Fast-Scan Cyclic Voltammetry in Human Studies.

Fast Scan Cyclic Voltammetry (FSCV) has been used for decades as a neurochemical tool for in vivo detection of phasic changes in electroactive neurotransmitters in animal models. Recently, multiple research groups have initiated human neurochemical studies using FSCV or demonstrated interest in bringing FSCV into clinical use. However, there remain technical challenges that limit clinical implementation of FSCV by creating barriers to appropriate scientific rigor and patient safety. In order to progress with clinical FSCV, these limitations must be first addressed through (1) appropriate pre-clinical studies to ensure accurate measurement of neurotransmitters and (2) the application of a risk management framework to assess patient safety. The intent of this work is to bring awareness of the current issues associated with FSCV to the scientific, engineering, and clinical communities and encourage them to seek solutions or alternatives that ensure data accuracy, rigor and reproducibility, and patient safety.

Motivating Self-Efficacy in Diverse Biomedical Science Post-baccalaureate and Graduate Students Through Scientific Conference Implementation.

Tactics to increase the number of underrepresented (UR) students in biomedical research PhD training programs have not yet translated to UR faculty numbers that reflect the diversity of the United States. Continued interventions are required to build skills beyond those that result in placement into a PhD program. We hypothesize that successful interventions must build skills that give UR students foundations for confident self-efficacy in leadership. We seek interventions that allow UR students to envision themselves as successful faculty. We posit that development of such skills is difficult in the classroom or laboratory alone. Therefore, novel interventions are required. As part of the NIH-funded Post-baccalaureate Research Education Program (PREP) and Initiative for Maximizing Student Development (IMSD) at the Mayo Clinic Graduate School of Biomedical Sciences, we designed and implemented a unique intervention to support development of student leadership skills: a biannual student-organized and student-led national research conference titled "Scientific Innovation Through Diverse Perspectives" (SITDP). This initiative is based on the concept that students who actively live out realistic roles as scientific leaders will be encouraged to persist to scientific leadership as faculty. Here we describe the motivation for, design of, and outcomes from, the first three pilot conferences of this series. We further discuss approaches needed to rigorously evaluate the effectiveness of such interventions in the future.

Simultaneous Ca2+ Imaging and Optogenetic Stimulation of Cortical Astrocytes in Adult Murine Brain Slices.

Astrocytes are actively involved in a neuroprotective role in the brain, which includes scavenging reactive oxygen species to minimize tissue damage. They also modulate neuroinflammation and reactive gliosis prevalent in several brain disorders like epilepsy, Alzheimer's, and Parkinson's disease. In animal models, targeted manipulation of astrocytic function via modulation of their calcium (Ca2+ ) oscillations by incorporating light-sensitive cation channels like Channelrhodopsin-2 (ChR2) offers a promising avenue in influencing the long-term progression of these disorders. However, using adult animals for Ca2+ imaging poses major challenges, including accelerated deterioration of in situ slice health and age- related changes. Additionally, optogenetic preparations necessitate usage of a red-shifted Ca2+ indicator like Rhod-2 AM to avoid overlapping light issues between ChR2 and the Ca2+ indicator during simultaneous optogenetic stimulation and imaging. In this article, we provide an experimental setting that uses live adult murine brain slices (2-5 months) from a knock-in model expressing Channelrhodopsin-2 (ChR2(C128S)) in cortical astrocytes, loaded with Rhod-2 AM to elicit robust Ca2+ response to light stimulation. We have developed and standardized a protocol for brain extraction, sectioning, Rhod-2 AM loading, maintenance of slice health, and Ca2+ imaging during light stimulation. This has been successfully applied to optogenetically control adult cortical astrocytes, which exhibit synchronous patterns of Ca2+ activity upon light stimulation, drastically different from resting spontaneous activity. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Experimental preparation, setup, slice preparation and Rhod-2 AM staining Basic Protocol 2: Image acquisition and analysis.

Developing Strategies for Sustainable Medical Equipment Maintenance in Under-Resourced Settings.

Engineering technology plays a pivotal role in the delivery of health care in under-resourced countries by providing an infrastructure to improve patient outcomes. However, sustainability of these technologies is difficult in these settings oftentimes due to limited resources or training. The framework presented in this editorial focuses on establishing medical and laboratory equipment sustainability in developing countries and is comprised of four steps: 1) establishing reliable in-country relationships with stakeholders, 2) identifying needs for sustainable solutions locally, 3) exploring potential solutions and assessing their effort-to-impact ratios, and 4) working with strategic partners to implement solutions with clear performance metrics. By focusing on the sustainability of donated equipment instead of the equipment itself, this method presented distinguishes itself from other philanthropic endeavors in the field by seeking to establish preventive maintenance habits that can impact clinical outcomes of a community long term. Application of this methodology is reported in the Original Research Article "A Low-Cost Humidity Control System to Protect Microscopes in a Tropical Climate" by Asp et. al.

A Low-Cost Humidity Control System to Protect Microscopes in a Tropical Climate.

Introduction: A clean and functional microscope is necessary for accurate diagnosis of infectious diseases. In tropical climates, high humidity levels and improper storage conditions allow for the accumulation of debris and fungus on the optical components of diagnostic equipment, such as microscopes. Objective: Our objective was to develop and implement a low-cost, sustainable, easy to manage, low-maintenance, passive humidity control chamber to both reduce debris accumulation and microbial growth onto the optical components of microscopes. Methods: Constructed from easily-sourced and locally available materials, the cost of each humidity control chamber is approximately $2.35 USD. Relative humidity levels were recorded every 30 minutes over a period of 10 weeks from two chambers deployed at the Belize Vector and Ecology Center and the University of Belize. Results: The humidity control chamber deployed at the University of Belize maintained internal relative humidity at an average of 35.3% (SD = 4.2%) over 10 weeks, while the average external relative humidity was 86.4% (SD = 12.4%). The humidity control chamber deployed at the Belize Vector and Ecology Center effectively maintained internal relative humidity to an average of 54.5% (SD = 9.4%) over 10 weeks, while the average external relative humidity was 86.9% (SD = 12.9%). Conclusions: Control of relative humidity is paramount for the sustainability of medical equipment in tropical climates. The humidity control chambers reduced relative humidity to levels that were not conducive for fungal growth while reducing microscope contamination from external sources. This will likely extend the service life of the microscopes while taking advantage of low-cost, locally sourced components.

Calcium imaging in freely-moving mice during electrical stimulation of deep brain structures.

After decades of study in humans and animal models, there remains a lack of consensus regarding how the action of electrical stimulation on neuronal and non-neuronal elements - e.g. neuropil, cell bodies, glial cells, etc. - leads to the therapeutic effects of neuromodulation therapies. To further our understanding of neuromodulation therapies, there is a critical need for novel methodological approaches using state-of-the-art neuroscience tools to study neuromodulation therapy in preclinical models of disease. In this manuscript we outline one such approach combining chronic behaving single-photon microendoscope recordings in a pathological mouse model with electrical stimulation of a common deep brain stimulation (DBS) target. We describe in detail the steps necessary to realize this approach, as well as discuss key considerations for extending this experimental paradigm to other DBS targets for different therapeutic indications. Additionally, we make recommendations from our experience on implementing and validating the required combination of procedures that includes: the induction of a pathological model (6-OHDA model of Parkinson's disease) through an injection procedure, the injection of the viral vector to induce GCaMP expression, the implantation of the GRIN lens and stimulation electrode, and the installation of a baseplate for mounting the microendoscope. We proactively identify unique data analysis confounds occurring due to the combination of electrical stimulation and optical recordings and outline an approach to address these confounds. In order to validate the technical feasibility of this unique combination of experimental methods, we present data to demonstrate that 1) despite the complex multifaceted surgical procedures, chronic optical recordings of hundreds of cells combined with stimulation is achievable over week long periods 2) this approach enables measurement of differences in DBS evoked neural activity between anesthetized and awake conditions and 3) this combination of techniques can be used to measure electrical stimulation induced changes in neural activity during behavior in a pathological mouse model. These findings are presented to underscore the feasibility and potential utility of minimally constrained optical recordings to elucidate the mechanisms of DBS therapies in animal models of disease.

Scientific societies fostering inclusivity through speaker diversity in annual meeting programming: a call to action.

Scientific societies aiming to foster inclusion of scientists from underrepresented (UR) backgrounds among their membership often delegate primary responsibility for this goal to a diversity-focused committee. The National Science Foundation has funded the creation of the Alliance to Catalyze Change for Equity in STEM Success (ACCESS), a meta-organization bringing together representatives from several such STEM society committees to serve as a hub for a growing community of practice. Our goal is to coordinate efforts to advance inclusive practices by sharing experiences and making synergistic discoveries about what works. ACCESS has analyzed the approaches by which member societies have sought to ensure inclusivity through selection of annual meeting speakers. Here we discuss how inclusive speaker selection fosters better scientific environments for all and identify challenges and promising practices for societies striving to maximize inclusivity of speakers in their scientific programming.

Scientific Societies Fostering Inclusive Scientific Environments through Travel Awards: Current Practices and Recommendations.

Diversity-focused committees continue to play essential roles in the efforts of professional scientific societies to foster inclusion and facilitate the professional development of underrepresented minority (URM) young scientists in their respective scientific disciplines. Until recently, the efforts of these committees have remained independent and disconnected from one another. Funding from the National Science Foundation has allowed several of these committees to come together and form the Alliance to Catalyze Change for Equity in STEM Success, herein referred to as ACCESS. The overall goal of this meta-organization is to create a community in which diversity-focused committees can interact, synergize, share their collective experiences, and have a unified voice on behalf of URM trainees in science, technology, engineering, and mathematics disciplines. In this Essay, we compare and contrast the broad approaches that scientific societies in ACCESS use to implement and assess their travel award programs for URM trainees. We also report a set of recommendations, including both short- and long-term outcomes assessment in populations of interest and specialized programmatic activities coupled to travel award programs.

Automated 3-dimensional brain atlas fitting to microelectrode recordings from deep brain stimulation surgeries.

OBJECTIVE: Deep brain stimulation (DBS) surgeries commonly rely on brain atlases and microelectrode recordings (MER) to help identify the target location for electrode implantation. We present an automated method for optimally fitting a 3-dimensional brain atlas to intraoperative MER and predicting a target DBS electrode location in stereotactic coordinates for the patient. METHODS: We retrospectively fit a 3-dimensional brain atlas to MER points from 10 DBS surgeries targeting the subthalamic nucleus (STN). We used a constrained optimization algorithm to maximize the MER points correctly fitted (i.e., contained) within the appropriate atlas nuclei. We compared our optimization approach to conventional anterior commissure-posterior commissure (AC/PC) scaling, and to manual fits performed by four experts. A theoretical DBS electrode target location in the dorsal STN was customized to each patient as part of the fitting process and compared to the location of the clinically defined therapeutic stimulation contact. RESULTS: The human expert and computer optimization fits achieved significantly better fits than the AC/PC scaling (80, 81, and 41% of correctly fitted MER, respectively). However, the optimization fits were performed in less time than the expert fits and converged to a single solution for each patient, eliminating interexpert variance. CONCLUSIONS AND SIGNIFICANCE: DBS therapeutic outcomes are directly related to electrode implantation accuracy. Our automated fitting techniques may aid in the surgical decision-making process by optimally integrating brain atlas and intraoperative neurophysiological data to provide a visual guide for target identification.

Tracking the mechanisms of deep brain stimulation for neuropsychiatric disorders.

Deep brain stimulation (DBS) has recently emerged as a potential treatment for medically intractable neuropsychiatric disorders. Pilot clinical studies with encouraging results have been performed with DBS of the ventral anterior internal capsule (VAIC) and subgenual cingulate white matter (Cg25WM) for the treatment of obsessive-compulsive disorder and depression. However, little is known about the underlying response of individual neurons, or the networks they are connected to, when DBS is applied to the VAIC or Cg25WM. This review summarizes current understanding of the response of axons to DBS, and discusses the general brain network architectures thought to underlie neuropsychiatric disorders. We also employ diffusion tensor imaging tractography to better understand the axonal trajectories surrounding DBS electrodes implanted in the VAIC or Cg25WM. Finally, we attempt to reconcile various data sets by presenting generalized hypotheses on potential therapeutic mechanisms of DBS for neuropsychiatric disease.

Design Choices for Next-Generation Neurotechnology Can Impact Motion Artifact in Electrophysiological and Fast-Scan Cyclic Voltammetry Measurements.

Implantable devices to measure neurochemical or electrical activity from the brain are mainstays of neuroscience research and have become increasingly utilized as enabling components of clinical therapies. In order to increase the number of recording channels on these devices while minimizing the immune response, flexible electrodes under 10 µm in diameter have been proposed as ideal next-generation neural interfaces. However, the representation of motion artifact during neurochemical or electrophysiological recordings using ultra-small, flexible electrodes remains unexplored. In this short communication, we characterize motion artifact generated by the movement of 7 µm diameter carbon fiber electrodes during electrophysiological recordings and fast-scan cyclic voltammetry (FSCV) measurements of electroactive neurochemicals. Through in vitro and in vivo experiments, we demonstrate that artifact induced by motion can be problematic to distinguish from the characteristic signals associated with recorded action potentials or neurochemical measurements. These results underscore that new electrode materials and recording paradigms can alter the representation of common sources of artifact in vivo and therefore must be carefully characterized.

Computational Modeling of Neurotransmitter Release Evoked by Electrical Stimulation: Nonlinear Approaches to Predicting Stimulation-Evoked Dopamine Release.

Neurochemical changes evoked by electrical stimulation of the nervous system have been linked to both therapeutic and undesired effects of neuromodulation therapies used to treat obsessive-compulsive disorder, depression, epilepsy, Parkinson's disease, stroke, hypertension, tinnitus, and many other indications. In fact, interest in better understanding the role of neurochemical signaling in neuromodulation therapies has been a focus of recent government- and industry-sponsored programs whose ultimate goal is to usher in an era of personalized medicine by creating neuromodulation therapies that respond to real-time changes in patient status. A key element to achieving these precision therapeutic interventions is the development of mathematical modeling approaches capable of describing the nonlinear transfer function between neuromodulation parameters and evoked neurochemical changes. Here, we propose two computational modeling frameworks, based on artificial neural networks (ANNs) and Volterra kernels, that can characterize the input/output transfer functions of stimulation-evoked neurochemical release. We evaluate the ability of these modeling frameworks to characterize subject-specific neurochemical kinetics by accurately describing stimulation-evoked dopamine release across rodent (R2 = 0.83 Volterra kernel, R2 = 0.86 ANN), swine (R2 = 0.90 Volterra kernel, R2 = 0.93 ANN), and non-human primate (R2 = 0.98 Volterra kernel, R2 = 0.96 ANN) models of brain stimulation. Ultimately, these models will not only improve understanding of neurochemical signaling in healthy and diseased brains but also facilitate the development of neuromodulation strategies capable of controlling neurochemical release via closed-loop strategies.