A history of deep brain stimulation: Technological innovation and the role of clinical assessment tools

Effects of cognitive behavioural therapy and exposure-response prevention on brain activation in obsessive-compulsive disorder patients: systematic review and meta-analysis

Current psychotherapeutic treatments for OCD, while effective, have complex outcomes with mixed efficacy. Previous research has observed baseline brain activation patterns in OCD patients, elucidating some of the implications of this disorder. Observing the effects of evidence-based psychotherapeutics for OCD on brain activation (through MRI) may provide a more comprehensive outline of pathology. This systematic review and meta-analysis evaluated the effects of cognitive behavioural therapy (CBT) with exposure-response prevention (ERP) on brain activation in OCD patients. Academic databases were systematically searched, and the outcomes evaluated included changes in brain activation and symptom severity between baseline and post-treatment. Patients (n = 193) had confirmed OCD diagnosis and underwent protocolized CBT with ERP programs delivered by trained therapists. Participants in the CBT with ERP programs demonstrated significant improvements in symptom severity (Cohen's d = - 1.91). In general, CBT with ERP resulted in decreased activation post-treatment in the frontal (Cohen's d = 0.40), parietal (Cohen's d = 0.79), temporal (Cohen's d = 1.02), and occipital lobe (Cohen's d = 0.76), and cerebellum (Cohen's d = - 0.78). The findings support CBT with ERP's ability to improve brain activation abnormalities in OCD patients. By identifying regions that improved activation levels, psychotherapy programs may benefit from the addition of function-specific features that could improve treatment outcomes.

The role of neuromodulation in the management of drug-resistant epilepsy

Drug-resistant epilepsy (DRE) poses significant challenges in terms of effective management and seizure control. Neuromodulation techniques have emerged as promising solutions for individuals who are unresponsive to pharmacological treatments, especially for those who are not good surgical candidates for surgical resection or laser interstitial therapy (LiTT). Currently, there are three neuromodulation techniques that are FDA-approved for the management of DRE. These include vagus nerve stimulation (VNS), deep brain stimulation (DBS), and responsive neurostimulation (RNS). Device selection, optimal time, and DBS and RNS target selection can also be challenging. In general, the number and localizability of the epileptic foci, alongside the comorbidities manifested by the patients, substantially influence the selection process. In the past, the general axiom was that DBS and VNS can be used for generalized and localized focal seizures, while RNS is typically reserved for patients with one or two highly localized epileptic foci, especially if they are in eloquent areas of the brain. Nowadays, with the advance in our understanding of thalamic involvement in DRE, RNS is also very effective for general non-focal epilepsy. In this review, we will discuss the underlying mechanisms of action, patient selection criteria, and the evidence supporting the use of each technique. Additionally, we explore emerging technologies and novel approaches in neuromodulation, such as closed-loop systems. Moreover, we examine the challenges and limitations associated with neuromodulation therapies, including adverse effects, complications, and the need for further long-term studies. This comprehensive review aims to provide valuable insights on present and future use of neuromodulation.

A perspective on translating genomic discoveries into targets for brain-machine interface and deep brain stimulation devices

Mental illnesses have a huge impact on individuals, families, and society, so there is a growing need for more efficient treatments. In this context, brain-computer interface (BCI) technology has the potential to revolutionize the options for neuropsychiatric therapies. However, the development of BCI-based therapies faces enormous challenges, such as power dissipation constraints, lack of credible feedback mechanisms, uncertainty of which brain areas and frequencies to target, and even which patients to treat. Some of these setbacks are due to the large gap in our understanding of brain function. In recent years, large-scale genomic analyses uncovered an unprecedented amount of information regarding the biology of the altered brain function observed across the psychopathology spectrum. We believe findings from genetic studies can be useful to refine BCI technology to develop novel treatment options for mental illnesses. Here, we assess the latest advancements in both fields, the possibilities that can be generated from their intersection, and the challenges that these research areas will need to address to ensure that translational efforts can lead to effective and reliable interventions. Specifically, starting from highlighting the overlap between mechanisms uncovered by large-scale genetic studies and the current targets of deep brain stimulation treatments, we describe the steps that could help to translate genomic discoveries into BCI targets. Because these two research areas have not been previously presented together, the present article can provide a novel perspective for scientists with different research backgrounds. This article is categorized under: Neurological Diseases > Genetics/Genomics/Epigenetics Neurological Diseases > Biomedical Engineering.

Application of deep brain stimulation for the treatment of childhood-onset dystonia in patients with MEPAN syndrome

Introduction

Mitochondrial Enoyl CoA Reductase Protein-Associated Neurodegeneration (MEPAN) syndrome is a rare inherited metabolic condition caused by MECR gene mutations. This gene encodes a protein essential for fatty acid synthesis, and defects cause progressively worsening childhood-onset dystonia, optic atrophy, and basal ganglia abnormalities. Deep brain stimulation (DBS) has shown mixed improvement in other childhood-onset dystonia conditions. To the best of our knowledge, DBS has not been investigated as a treatment for dystonia in patients with MEPAN syndrome.

Methods

Two children with MEPAN were identified as possible DBS candidates due to severe generalized dystonia unresponsive to pharmacotherapy. Temporary depth electrodes were placed in six locations bilaterally and tested during a 6-day hospitalization to determine the best locations for permanent electrode placement. The Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) and Barry-Albright Dystonia Scale (BADS) were used for preoperative and postoperative testing to quantitatively assess dystonia severity changes. Patient 1 had permanent electrodes placed at the globus pallidus internus (GPi) and pedunculopontine nucleus (PPN). Patient 2 had permanent electrodes placed at the GPi and ventralis intermedius nucleus of the thalamus (VIM).

Results

Both patients successfully underwent DBS placement with no perioperative complications and significant improvement in their BFMDRS score. Patient 2 also demonstrated improvement in the BADS.

Discussion

We demonstrated a novel application of DBS in MEPAN syndrome patients with childhood-onset dystonia. These patients showed clinically significant improvements in dystonia following DBS, indicating that DBS can be considered for dystonia in patients with rare metabolic disorders that currently have no other proven treatment options.

Closing the loop in psychiatric deep brain stimulation: physiology, psychometrics, and plasticity

Deep brain stimulation (DBS) is an invasive approach to precise modulation of psychiatrically relevant circuits. Although it has impressive results in open-label psychiatric trials, DBS has also struggled to scale to and pass through multi-center randomized trials. This contrasts with Parkinson disease, where DBS is an established therapy treating thousands of patients annually. The core difference between these clinical applications is the difficulty of proving target engagement, and of leveraging the wide range of possible settings (parameters) that can be programmed in a given patient's DBS. In Parkinson's, patients' symptoms change rapidly and visibly when the stimulator is tuned to the correct parameters. In psychiatry, those same changes take days to weeks, limiting a clinician's ability to explore parameter space and identify patient-specific optimal settings. I review new approaches to psychiatric target engagement, with an emphasis on major depressive disorder (MDD). Specifically, I argue that better engagement may come by focusing on the root causes of psychiatric illness: dysfunction in specific, measurable cognitive functions and in the connectivity and synchrony of distributed brain circuits. I overview recent progress in both those domains, and how it may relate to other technologies discussed in companion articles in this issue.

Deep Brain Stimulation for the Management of Refractory Neurological Disorders: A Comprehensive Review

In recent decades, deep brain stimulation (DBS) has been extensively studied due to its reversibility and significantly fewer side effects. DBS is mainly a symptomatic therapy, but the stimulation of subcortical areas by DBS is believed to affect the cytoarchitecture of the brain, leading to adaptability and neurogenesis. The neurological disorders most commonly studied with DBS were Parkinson's disease, essential tremor, obsessive-compulsive disorder, and major depressive disorder. The most precise approach to evaluating the location of the leads still relies on the stimulus-induced side effects reported by the patients. Moreover, the adequate voltage and DBS current field could correlate with the patient's symptoms. Implantable pulse generators are the main parts of the DBS, and their main characteristics, such as rechargeable capability, magnetic resonance imaging (MRI) safety, and device size, should always be discussed with patients. The safety of MRI will depend on several parameters: the part of the body where the device is implanted, the part of the body scanned, and the MRI-tesla magnetic field. It is worth mentioning that drug-resistant individuals may have different pathophysiological explanations for their resistance to medications, which could affect the efficacy of DBS therapy. Therefore, this could explain the significant difference in the outcomes of studies with DBS in individuals with drug-resistant neurological conditions.

The American Society of Pain and Neuroscience (ASPN) Guidelines for Radiofrequency Ablative Procedures in Patients with Implanted Devices

Radiofrequency ablation (RFA) is a treatment modality used in interventional pain management to treat several conditions including chronic neck or back pain, sacroiliac joint pain, major joint pain, and pain from sites that can be isolated to a sensory nerve amenable to RFA. The goals of such procedures are to reduce pain, improve function, delay need for surgical intervention, and reduce pain medication consumption. As applications for RFA expand through novel techniques and nerve targets, there is concern with how RFA may impact patients with implanted medical devices. Specifically, the electrical currents used in RFA produce electromagnetic interference, which can result in unintentional energy transfer to implanted devices. This may also interfere with device function or cause damage to the device itself. As the number of patients with implanted devices increases, it is imperative to establish guidelines for the management of implanted devices during RFA procedures. This review aims to establish guidelines to assist physicians in the preoperative, intraoperative, and postoperative management of implanted devices in patients undergoing procedures using radiofrequency energy. Here, we provide physicians with background knowledge and a summary of current evidence to allow safe utilization of RFA treatment in patients with implanted devices such as cardiac implantable electronic devices, spinal cord stimulators, intrathecal pumps, and deep brain stimulators. While these guidelines are intended to be comprehensive, each patient should be assessed on an individual basis to optimize outcomes.

Neurosurgical management of non-spastic movement disorders

BACKGROUND

Non-spastic movement disorders in children are common, although true epidemiologic data is difficult to ascertain. Children are more likely than adults to have hyperkinetic movement disorders defined as tics, dystonia, chorea/athetosis, or tremor. These conditions manifest from acquired or heredodegenerative etiologies and often severely limit function despite medical and surgical management paradigms. Neurosurgical management for these conditions is highlighted.

METHODS

We performed a focused review of the literature by searching PubMed on 16 May 2023 using key terms related to our review. No temporal filter was applied, but only English articles were considered. We searched for the terms (("Pallidotomy"[Mesh]) OR "Rhizotomy"[Mesh]) OR "Deep Brain Stimulation"[Mesh], dystonia, children, adolescent, pediatric, globus pallidus, in combination. All articles were reviewed for inclusion in the final reference list.

RESULTS

Our search terms returned 37 articles from 2004 to 2023. Articles covering deep brain stimulation were the most common (n = 34) followed by pallidotomy (n = 3); there were no articles on rhizotomy.

DISCUSSION

Non-spastic movement disorders are common in children and difficult to treat. Most of these patients are referred to neurosurgery for the management of dystonia, with modern neurosurgical management including pallidotomy, rhizotomy, and deep brain stimulation. Historically, pallidotomy has been effective and may still be preferred in subpopulations presenting either in status dystonicus or with high risk for hardware complications. Superiority of DBS over pallidotomy for secondary dystonia has not been determined. Rhizotomy is an underutilized surgical tool and more study characterizing efficacy and risk profile is indicated.

Preliminary Experience with a Four-Lead Implantable Pulse Generator for Deep Brain Stimulation

BACKGROUND

Implantable pulse generators (IPGs) store energy and deliver electrical impulses for deep brain stimulation (DBS) to treat neurological and psychiatric disorders. IPGs have evolved over time to meet the demands of expanding clinical indications and more nuanced therapeutic approaches.

OBJECTIVES

The aim of this study was to examine the workflow of the first 4-lead IPG for DBS in patients with complex disease.

METHOD

The engineering capabilities, clinical use cases, and surgical technique are described in a cohort of 12 patients with epilepsy, essential tremor, Parkinson's disease, mixed tremor, and Tourette's syndrome with comorbid obsessive-compulsive disorder between July 2021 and July 2022.

RESULTS

This system is a rechargeable 32-channel, 4-port system with independent current control that can be connected to 8 contact linear or directionally segmented leads. The system is ideal for patients with mixed disease or those with multiple severe symptoms amenable to >2 lead implantations. A multidisciplinary team including neurologists, radiologists, and neurosurgeons is necessary to safely plan the procedure. There were no serious intraoperative or postoperative adverse events. One patient required revision surgery for bowstringing.

CONCLUSIONS

This new 4-lead IPG represents an important new tool for DBS surgery with the ability to expand lead implantation paradigms for patients with complex disease.

A protocol of a systematic review on deep brain stimulation surgery and its efficacy in addressing substance abuse addiction

Background

Pharmacotherapy and psychotherapeutic approaches are still the mainstay first line of treatment for substance use disorder. However, the path to rehabilitation and cessation of dependence often proves uncertain and laborious, with risks of relapse being considerable despite exposure to current therapeutic modalities. For cases of treatment-refractory addiction, deep brain stimulation (DBS) interventions can prove a more effective long term therapeutic solution for the patient.

Objectives

The aim of the study will be to systematically assess whether attempts at correcting substance use disorder via DBS neurosurgical interventions have been successful in inducing remission or ameliorating relapse rates.

Methods

The current study will analyze available literature from database inception up to 15th April 2023, reviewing all publications documenting results achieved with human patients undergoing DBS for substance use disorder in PubMed, Ovid, Cochrane, and Web of Science. The electronic database search will exclude animal studies in the field and focus solely on the application of DBS for the purposes of addressing addiction disorders.

Results

The expectation is for a reduced number of trial results to have been reported, namely due to the relatively recent application of DBS to address severe addiction. Nonetheless, numbers should be in sufficient amount to inform about the efficacy of the intervention.

Conclusion

This study will attempt to demonstrate the viability of DBS as a solution for tackling treatment-refractory substance use disorder, proposing it as a valid therapeutic option that can deliver robust results and help combat an expanding societal plague that is drug dependence.

Network targets for therapeutic brain stimulation: towards personalized therapy for pain

Precision neuromodulation of central brain circuits is a promising emerging therapeutic modality for a variety of neuropsychiatric disorders. Reliably identifying in whom, where, and in what context to provide brain stimulation for optimal pain relief are fundamental challenges limiting the widespread implementation of central neuromodulation treatments for chronic pain. Current approaches to brain stimulation target empirically derived regions of interest to the disorder or targets with strong connections to these regions. However, complex, multidimensional experiences like chronic pain are more closely linked to patterns of coordinated activity across distributed large-scale functional networks. Recent advances in precision network neuroscience indicate that these networks are highly variable in their neuroanatomical organization across individuals. Here we review accumulating evidence that variable central representations of pain will likely pose a major barrier to implementation of population-derived analgesic brain stimulation targets. We propose network-level estimates as a more valid, robust, and reliable way to stratify personalized candidate regions. Finally, we review key background, methods, and implications for developing network topology-informed brain stimulation targets for chronic pain.

The Role of Family Members in Psychiatric Deep Brain Stimulation Trials: More Than Psychosocial Support

Family members can provide crucial support to individuals participating in clinical trials. In research on the "newest frontier" of Deep Brain Stimulation (DBS)-the use of DBS for psychiatric conditions-family member support is frequently listed as a criterion for trial enrollment. Despite the significance of family members, qualitative ethics research on DBS for psychiatric conditions has focused almost exclusively on the perspectives and experiences of DBS recipients. This qualitative study is one of the first to include both DBS recipients and their family members as interview participants. Using dyadic thematic analysis-an approach that takes both the individuals and the relationship as units of analyses-this study analyzes the complex ways in which family relationships can affect DBS trial participation, and how DBS trial participation in turn influences family relationships. Based on these findings, we propose ways to improve study designs to better take family relationships into account, and better support family members in taking on the complex, essential roles that they play in DBS trials for psychiatric conditions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12152-023-09520-7.

In silicodevelopment and validation of Bayesian methods for optimizing deep brain stimulation to enhance cognitive control

Objective.deep brain stimulation (DBS) of the ventral internal capsule/striatum (VCVS) is a potentially effective treatment for several mental health disorders when conventional therapeutics fail. Its effectiveness, however, depends on correct programming to engage VCVS sub-circuits. VCVS programming is currently an iterative, time-consuming process, with weeks between setting changes and reliance on noisy, subjective self-reports. An objective measure of circuit engagement might allow individual settings to be tested in seconds to minutes, reducing the time to response and increasing patient and clinician confidence in the chosen settings. Here, we present an approach to measuring and optimizing that circuit engagement.Approach.we leverage prior results showing that effective VCVS DBS engages cognitive control circuitry and improves performance on the multi-source interference task, that this engagement depends primarily on which contact(s) are activated, and that circuit engagement can be tracked through a state space modeling framework. We develop a simulation framework based on those empirical results, then combine this framework with an adaptive optimizer to simulate a principled exploration of electrode contacts and identify the contacts that maximally improve cognitive control. We explore multiple optimization options (algorithms, number of inputs, speed of stimulation parameter changes) and compare them on problems of varying difficulty.Main results.we show that an upper confidence bound algorithm outperforms other optimizers, with roughly 80% probability of convergence to a global optimum when used in a majority-vote ensemble.Significance.we show that the optimization can converge even with lag between stimulation and effect, and that a complete optimization can be done in a clinically feasible timespan (a few hours). Further, the approach requires no specialized recording or imaging hardware, and thus could be a scalable path to expand the use of DBS in psychiatric and other non-motor applications.

Landscape and future directions of machine learning applications in closed-loop brain stimulation

Brain stimulation (BStim) encompasses multiple modalities (e.g., deep brain stimulation, responsive neurostimulation) that utilize electrodes implanted in deep brain structures to treat neurological disorders. Currently, BStim is primarily used to treat movement disorders such as Parkinson's, though indications are expanding to include neuropsychiatric disorders like depression and schizophrenia. Traditional BStim systems are "open-loop" and deliver constant electrical stimulation based on manually-determined parameters. Advancements in BStim have enabled development of "closed-loop" systems that analyze neural biomarkers (e.g., local field potentials in the sub-thalamic nucleus) and adjust electrical modulation in a dynamic, patient-specific, and energy efficient manner. These closed-loop systems enable real-time, context-specific stimulation adjustment to reduce symptom burden. Machine learning (ML) has emerged as a vital component in designing these closed-loop systems as ML models can predict / identify presence of disease symptoms based on neural activity and adaptively learn to modulate stimulation. We queried the US National Library of Medicine PubMed database to understand the role of ML in developing closed-loop BStim systems to treat epilepsy, movement disorders, and neuropsychiatric disorders. Both neural and non-neural network ML algorithms have successfully been leveraged to create closed-loop systems that perform comparably to open-loop systems. For disorders in which the underlying neural pathophysiology is relatively well understood (e.g., Parkinson's, essential tremor), most work has involved refining ML models that can classify neural signals as aberrant or normal. The same is seen for epilepsy, where most current research has focused on identifying optimal ML model design and integrating closed-loop systems into existing devices. For neuropsychiatric disorders, where the underlying pathologic neural circuitry is still being investigated, research is focused on identifying biomarkers (e.g., local field potentials from brain nuclei) that ML models can use to identify onset of symptoms and stratify severity of disease.

Beauty and death of motion

Translational research aims to apply what we learn in the lab to the patient's care in the clinical setting. Animal studies for Parkinson's disease and Deep Brain Stimulation (DBS) are particularly intriguing topics that show the value of translational research. Training a monkey to complete a task, inducing Parkinsonian symptoms, and comparing kinematic differences with various DBS settings is a transformative process of motion creation, death, and rebirth. The historical context of the drug used to induce Parkinsonian symptoms and DBS technology demonstrates how our field progresses from trial and error and evolves into enhancing patient care. We can use the same methods from animal studies to verify outcomes during a patient's DBS surgery. The narrative of one monkey demonstrates the concepts of translational research, research ethics, and medical history.

Suicide in Deep Brain Stimulation for Parkinson's Disease: A Retrospective Case-Control Study

 Deep brain stimulation (DBS), a treatment of Parkinson's disease (PD), has been associated with suicidality. We conducted a case-control study comparing suicide in four pairs of cohorts: PD patients with DBS or not, epilepsy patients with resection surgery or not, subjects with BMI≥30 with bariatric surgery or not, and patients with chronic kidney disease with transplantation or not. PD patients with DBS demonstrated a lower risk of suicide relative to PD patients without DBS. Findings from other elective surgeries indicate that patients receiving operative treatments do not possess predictable differences in suicide rates relative to their medically managed counterparts.

Nanomedicine and nanobiotechnology applications of magnetoelectric nanoparticles

Unlike any other nanoparticles known to date, magnetoelectric nanoparticles (MENPs) can generate relatively strong electric fields locally via the application of magnetic fields and, vice versa, have their magnetization change in response to an electric field from the microenvironment. Hence, MENPs can serve as a wireless two-way interface between man-made devices and physiological systems at the molecular level. With the recent development of room-temperature biocompatible MENPs, a number of novel potential medical applications have emerged. These applications include wireless brain stimulation and mapping/recording of neural activity in real-time, targeted delivery across the blood-brain barrier (BBB), tissue regeneration, high-specificity cancer cures, molecular-level rapid diagnostics, and others. Several independent in vivo studies, using mice and nonhuman primates models, demonstrated the capability to deliver MENPs in the brain across the BBB via intravenous injection or, alternatively, bypassing the BBB via intranasal inhalation of the nanoparticles. Wireless deep brain stimulation with MENPs was demonstrated both in vitro and in vivo in different rodents models by several independent groups. High-specificity cancer treatment methods as well as tissue regeneration approaches with MENPs were proposed and demonstrated in in vitro models. A number of in vitro and in vivo studies were dedicated to understand the underlying mechanisms of MENPs-based high-specificity targeted drug delivery via application of d.c. and a.c. magnetic fields. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies.

The Aversive Lens: Stress effects on the prefrontal-cingulate cortical pathways that regulate emotion

ARNSTEN, A.F.T., M.K.P. Joyce and A.C. Roberts. The Aversive Lens: Stress effects on the prefrontal-cingulate cortical pathways that regulate emotion. NEUROSCI BIOBEHAV REV XXX-XXX, 2022. The symptoms of major-depressive-disorder include psychic pain and anhedonia, i.e. seeing the world through an "aversive lens". The neurobiology underlying this shift in worldview is emerging. Here these data are reviewed, focusing on how activation of subgenual cingulate (BA25) induces an "aversive lens", and how higher prefrontal cortical (PFC) areas (BA46/10/32) provide top-down regulation of BA25 but are weakened by excessive dopamine and norepinephrine release during stress exposure, and dendritic spine loss with chronic stress exposure. These changes may generate an attractor state, which maintains the brain under the control of BA25, requiring medication or neuromodulatory treatments to return connectivity to a more flexible state. In line with this hypothesis, effective anti-depressant treatments reduce the activity of BA25 and restore top-down regulation by higher circuits, e.g. as seen with SSRI medications, ketamine, deep brain stimulation of BA25, or rTMS to strengthen dorsolateral PFC. This research has special relevance in an era of chronic stress caused by the COVID19 pandemic, political unrest and threat of climate change.

Functional Two-Dimensional Materials for Bioelectronic Neural Interfacing

Realizing the neurological information processing by analyzing the complex data transferring behavior of populations and individual neurons is one of the fast-growing fields of neuroscience and bioelectronic technologies. This field is anticipated to cover a wide range of advanced applications, including neural dynamic monitoring, understanding the neurological disorders, human brain-machine communications and even ambitious mind-controlled prosthetic implant systems. To fulfill the requirements of high spatial and temporal resolution recording of neural activities, electrical, optical and biosensing technologies are combined to develop multifunctional bioelectronic and neuro-signal probes. Advanced two-dimensional (2D) layered materials such as graphene, graphene oxide, transition metal dichalcogenides and MXenes with their atomic-layer thickness and multifunctional capabilities show bio-stimulation and multiple sensing properties. These characteristics are beneficial factors for development of ultrathin-film electrodes for flexible neural interfacing with minimum invasive chronic interfaces to the brain cells and cortex. The combination of incredible properties of 2D nanostructure places them in a unique position, as the main materials of choice, for multifunctional reception of neural activities. The current review highlights the recent achievements in 2D-based bioelectronic systems for monitoring of biophysiological indicators and biosignals at neural interfaces.

Bio-inspired conductive adhesive based on calcium-free alginate hydrogels for bioelectronic interfaces

Electrode impedance is one of the greatest challenges facing neural interfacing medical devices and the use of electrical stimulation-based therapies in the fields of neurology and regenerative medicine. Maximizing contact between electronics and tissue would allow for more accurate recordings of neural activity and to stimulate with less power in implantable devices as electric signals could be more precisely transferred by a stable interfacial area. Neural environments, inherently wet and ion-rich, present a unique challenge for traditional conductive adhesives. As such, we look to marine mussels that use a 3,4-dihydroxyphenyl-L-analine (DOPA)-containing proteinaceous excretion to adhere to a variety of substrates for inspiration. By functionalizing alginate, which is an abundantly available natural polymer, with the catechol residues DOPA contains, we developed a hydrogel-based matrix to which carbon-based nanofiller was added to render it conductive. The synthesized product had adhesive energy within the range of previously reported mussel-based polymers, good electrical properties and was not cytotoxic to brain derived neural precursor cells.

Facile Fabrication of Injectable Alginate and Poly(3,4-ethylenedioxythiophene)-Based Soft Electrodes toward the Goal of Neuro-Regenerative Applications

Resident brain neural precursor cells (NPCs) are electrosensitive cells that respond to electric field application by proliferating, differentiating, and undergoing rapid and directed cathodal migration. Harnessing NPC potential is a promising strategy to facilitate neural repair following injury or disease. The use of electric fields to activate NPCs is limited by current electrode designs which are typically made of conductive metals that are stiff and can lead to neuroinflammation following implantation, in part due to the mechanical mismatch between physiological conditions and material. Herein, the design of a novel, injectable biobased soft electrode with properties suitable for electrical stimulation in vivo is explored. The recent interest in using biologically derived polymers which are relatively abundant and afford economic feasibility have been built upon. Sodium alginate is utilized to form soft hydrogels, thereby addressing the issue of mechanical mismatch, and the conductive polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), to generate an innovative new material. It is demonstrated that the optimized alginate PEDOT blend matches the modulus of the brain and is suitable for injection and is not cytotoxic to neural cells. Furthermore, in vivo studies demonstrate minimal activation of inflammatory cells upon implantation in the brain compared to classically used platinum-based electrodes.

Magnetic-field-synchronized wireless modulation of neural activity by magnetoelectric nanoparticles

The in vitro study demonstrates wirelessly controlled modulation of neural activity using magnetoelectric nanoparticles (MENPs), synchronized to magnetic field application with a sub-25-msec temporal response. Herein, MENPs are sub-30-nm CoFe₂O₄@BaTiO₃ core-shell nanostructures. MENPs were added to E18 rat hippocampal cell cultures (0.5 μg of MENPs per 100,000 neurons) tagged with fluorescent Ca²⁺ sensitive indicator cal520. MENPs were shown to wirelessly induce calcium transients which were synchronized with application of 1200-Oe bipolar 25-msec magnetic pulses at a rate of 20 pulses/sec. The observed calcium transients were similar, in shape and magnitude, to those generated through the control electric field stimulation with a 50-μA current, and they were inhibited by the sodium channel blocker tetrodotoxin. The observed MENP-based magnetic excitation of neural activity is in agreement with the non-linear M - H hysteresis loop of the MENPs, wherein the MENPs' coercivity value sets the threshold for the externally applied magnetic field.

Towards network-guided neuromodulation for epilepsy

Epilepsy is well-recognized as a disorder of brain networks. There is a growing body of research to identify critical nodes within dynamic epileptic networks with the aim to target therapies that halt the onset and propagation of seizures. In parallel, intracranial neuromodulation, including deep brain stimulation and responsive neurostimulation, are well-established and expanding as therapies to reduce seizures in adults with focal-onset epilepsy; and there is emerging evidence for their efficacy in children and generalized-onset seizure disorders. The convergence of these advancing fields is driving an era of 'network-guided neuromodulation' for epilepsy. In this review, we distil the current literature on network mechanisms underlying neurostimulation for epilepsy. We discuss the modulation of key 'propagation points' in the epileptogenic network, focusing primarily on thalamic nuclei targeted in current clinical practice. These include (i) the anterior nucleus of thalamus, now a clinically approved and targeted site for open loop stimulation, and increasingly targeted for responsive neurostimulation; and (ii) the centromedian nucleus of the thalamus, a target for both deep brain stimulation and responsive neurostimulation in generalized-onset epilepsies. We discuss briefly the networks associated with other emerging neuromodulation targets, such as the pulvinar of the thalamus, piriform cortex, septal area, subthalamic nucleus, cerebellum and others. We report synergistic findings garnered from multiple modalities of investigation that have revealed structural and functional networks associated with these propagation points - including scalp and invasive EEG, and diffusion and functional MRI. We also report on intracranial recordings from implanted devices which provide us data on the dynamic networks we are aiming to modulate. Finally, we review the continuing evolution of network-guided neuromodulation for epilepsy to accelerate progress towards two translational goals: (i) to use pre-surgical network analyses to determine patient candidacy for neurostimulation for epilepsy by providing network biomarkers that predict efficacy; and (ii) to deliver precise, personalized and effective antiepileptic stimulation to prevent and arrest seizure propagation through mapping and modulation of each patients' individual epileptogenic networks.

Non-Pharmacological Therapeutic Options for the Treatment of Alzheimer’s Disease

Alzheimer’s disease is a growing global crisis in need of urgent diagnostic and therapeutic strategies. The current treatment strategy mostly involves immunotherapeutic medications that have had little success in halting disease progress. Hypotheses for pathogenesis and development of AD have been expanded to implicate both organ systems as well as cellular reactions. Non-pharmacologic interventions ranging from minimally to deeply invasive have attempted to address these diverse contributors to AD. In this review, we aim to delineate mechanisms underlying such interventions while attempting to provide explanatory links between the observed differences in disease states and postulated metabolic or structural mechanisms of change. The techniques discussed are not an exhaustive list of non-pharmacological interventions against AD but provide a foundation to facilitate a deeper understanding of the area of study.

Transcranial ultrasound neuromodulation induces neuronal correlation change in the rat somatosensory cortex

Objective.Transcranial focused ultrasound (tFUS) is a neuromodulation technique which has been the focus of increasing interest for noninvasive brain stimulation with high spatial specificity. Its ability to excite and inhibit neural circuits as well as to modulate perception and behavior has been demonstrated, however, we currently lack understanding of how tFUS modulates the ways neurons interact with each other. This understanding would help elucidate tFUS's mechanism of systemic neuromodulation and allow future development of therapies for treating neurological disorders.Approach.In this study, we investigate how tFUS modulates neural interaction and response to peripheral electrical limb stimulation through intracranial multi-electrode recordings in the rat somatosensory cortex. We deliver ultrasound in a pulsed pattern to induce frequency dependent plasticity in a manner similar to what is found following electrical stimulation.Main Results.We show that neural firing in response to peripheral electrical stimulation is increased after ultrasound stimulation at all frequencies, showing tFUS induced changes in excitability of individual neuronsin vivo. We demonstrate tFUS sonication repetition frequency dependent pairwise correlation changes between neurons, with both increases and decreases observed at different frequencies.Significance.These results extend previous research showing tFUS to be capable of inducing synaptic depression and demonstrate its ability to modulate network dynamics as a whole.

The limitations of investigating appetite through circuit manipulations: are we biting off more than we can chew?

Disordered eating can underpin a number of debilitating and prevalent chronic diseases, such as obesity. Broader advances in psychopharmacology and biology have motivated some neuroscientists to address diet-induced obesity through reductionist, pre-clinical eating investigations on the rodent brain. Specifically, chemogenetic and optogenetic methods developed in the 21st century allow neuroscientists to perform in vivo, region-specific/projection-specific/promoter-specific circuit manipulations and immediately assess the impact of these manipulations on rodent feeding. These studies are able to rigorously conclude whether a specific neuronal population regulates feeding behaviour in the hope of eventually developing a mechanistic neuroanatomical map of appetite regulation. However, an artificially stimulated/inhibited rodent neuronal population that changes feeding behaviour does not necessarily represent a pharmacological target for treating eating disorders in humans. Chemogenetic/optogenetic findings must therefore be triangulated with the array of theories that contribute to our understanding of appetite. The objective of this review is to provide a wide-ranging discussion of the limitations of chemogenetic/optogenetic circuit manipulation experiments in rodents that are used to investigate appetite. Stepping into and outside of medical science epistemologies, this paper draws on philosophy of science, nutrition, addiction biology and neurophilosophy to prompt more integrative, transdisciplinary interpretations of chemogenetic/optogenetic appetite data. Through discussing the various technical and epistemological limitations of these data, we provide both an overview of chemogenetics and optogenetics accessible to non-neuroscientist obesity researchers, as well as a resource for neuroscientists to expand the number of lenses through which they interpret their circuit manipulation findings.

On-Demand Chemomagnetic Modulation of Striatal Neurons Facilitated by Hybrid Magnetic Nanoparticles

Minimally invasive manipulation of cell signaling is critical in basic neuroscience research and in developing therapies for neurological disorders. Here, we describe a wireless chemomagnetic neuromodulation platform for the on-demand control of primary striatal neurons that relies on nanoscale heating events. Iron oxide magnetic nanoparticles (MNPs) are functionally coated with thermoresponsive poly (oligo (ethylene glycol) methyl ether methacrylate) (POEGMA) brushes loaded with dopamine. Dopamine loaded MNPs-POEGMA are co-cultured with primary striatal neurons. When alternating magnetinec fields (AMF) are applied, MNPs undergo hysteresis power loss and dissipate heat. The local heat produced by MNPs initiates a thermodynamic phase transition on POEGMA brushes resulting in polymer collapse and dopamine release. AMF-triggered dopamine release enhances the response of dopamine ion channels expressed on the cell membranes enhancing the activity of ~50% of striatal neurons subjected to the treatment. Chemomagnetic actuation on dopamine receptors is confirmed by blocking D1 and D2 receptors. The reversible thermodynamic phase transition of POEGMA brushes allow the on-demand release of dopamine in multiple microdoses. AMF-triggered dopamine release from MNPs-POEGMA causes no cell cytotoxicity nor promotes cell ROS production. This research represents a fundamental step forward for the chemomagnetic control of neural activity using hybrid magnetic nanomaterials with tailored physical properties.

Femtosecond laser hierarchical surface restructuring for next generation neural interfacing electrodes and microelectrode arrays

Long-term implantable neural interfacing devices are able to diagnose, monitor, and treat many cardiac, neurological, retinal and hearing disorders through nerve stimulation, as well as sensing and recording electrical signals to and from neural tissue. To improve specificity, functionality, and performance of these devices, the electrodes and microelectrode arrays-that are the basis of most emerging devices-must be further miniaturized and must possess exceptional electrochemical performance and charge exchange characteristics with neural tissue. In this report, we show for the first time that the electrochemical performance of femtosecond-laser hierarchically-restructured electrodes can be tuned to yield unprecedented performance values that significantly exceed those reported in the literature, e.g. charge storage capacity and specific capacitance were shown to have improved by two orders of magnitude and over 700-fold, respectively, compared to un-restructured electrodes. Additionally, correlation amongst laser parameters, electrochemical performance and surface parameters of the electrodes was established, and while performance metrics exhibit a relatively consistent increasing behavior with laser parameters, surface parameters tend to follow a less predictable trend negating a direct relationship between these surface parameters and performance. To answer the question of what drives such performance and tunability, and whether the widely adopted reasoning of increased surface area and roughening of the electrodes are the key contributors to the observed increase in performance, cross-sectional analysis of the electrodes using focused ion beam shows, for the first time, the existence of subsurface features that may have contributed to the observed electrochemical performance enhancements. This report is the first time that such performance enhancement and tunability are reported for femtosecond-laser hierarchically-restructured electrodes for neural interfacing applications.

Implantable acousto-optic window for monitoring ultrasound-mediated neuromodulation in vivo

Significance: Ultrasound has recently received considerable attention in neuroscience because it provides noninvasive control of deep brain activity. Although the feasibility of ultrasound stimulation has been reported in preclinical and clinical settings, its mechanistic understanding remains limited. While optical microscopy has become the "gold standard" tool for investigating population-level neural functions in vivo, its application for ultrasound neuromodulation has been technically challenging, as most conventional ultrasonic transducers are not designed to be compatible with optical microscopy. Aim: We aimed to develop a transparent acoustic transducer based on a glass coverslip called the acousto-optic window (AOW), which simultaneously provides ultrasound neuromodulation and microscopic monitoring of neural responses in vivo. Approach: The AOW was fabricated by the serial deposition of transparent acoustic stacks on a circular glass coverslip, comprising a piezoelectric material, polyvinylidene fluoride-trifluoroethylene, and indium-tin-oxide electrodes. The fabricated AOW was implanted into a transgenic neural-activity reporter mouse after open craniotomy. Two-photon microscopy was used to observe neuronal activity in response to ultrasonic stimulation through the AOW. Results: The AOW allowed microscopic imaging of calcium activity in cortical neurons in response to ultrasound stimulation. The optical transparency was ∼ 40 % over the visible and near-infrared spectra, and the ultrasonic pressure was 0.035 MPa at 10 MHz corresponding to 10    mW / cm 2 . In anesthetized Gad2-GCaMP6-tdTomato mice, we observed robust ultrasound-evoked activation of inhibitory cortical neurons at depths up to 200    μ m . Conclusions: The AOW is an implantable ultrasonic transducer that is broadly compatible with optical imaging modalities. The AOW will facilitate our understanding of ultrasound neuromodulation in vivo.

A comparison of an implanted accelerometer with a wearable accelerometer for closed-loop DBS

Sensing technology, as well as cloud communication, is enabling the development of closed-loop deep brain stimulation (DBS) for Parkinson's disease. The accelerometer is a practical sensor that can provide information about the disease/health state of the patient as well as physical activity levels, all of which in the long-term can provide feedback information to an adaptive closed-loop control algorithm for more effective and personalized DBS therapy. In this paper, we present for the first time, acceleration streamed from Medtronic's RC+S device in patients with Parkinson's disease while at home, and compare it to accel-eration acquired concurrently from the patient's Apple Watch. We examined correlation between the accelerometer signals at varying time scales. We also compared the spectral band power obtained from the two accelerometers. While there was an average correlation of 0.37 for subject 1 and 0.50 for subject 2 between the two acceleration signals on a time scale of 10 minutes, the correlation was lower for shorter time scales on the order of seconds. There was greater spectral power in the Parkinsonian tremor band of 4-7 Hz for the externally worn accelerometer than the internal accelerometer, but the internal accelerometer showed greater relative power distributed in the higher frequencies (7-30 Hz). Thus, based on this preliminary analysis, we expect that the internal accelerometer may be used to assess patient activity and state for closed loop DBS but tremor detection may require more sophisticated signal processing. Furthermore, the internal accelerometer may contain information in higher frequency bands that reveal information about the patient state. Clinical relevance - Closed-loop DBS is expected to improve patient outcomes for the tens of thousands of Parkinson's disease patients using DBS [1], [2]. Eliminating an additional external device in order to implement closed-loop adaptive deep brain stimulation would benefit DBS patients however an understanding of what information is lost by doing so is needed to justify the ultimate design of closed-loop DBS.

Stereotactic surgeries for abuse syndromes: Patient selection and results

It is known that in present time heroin addiction is the most widespread and difficult to treat. It includes two factors: physical and psychological addiction. The vast majority of patients remained mentally addicted to drugs after physical drug addiction has been eliminated and the organism has been completely detoxed. It is an indomitable desire to take drugs. Neurophysiological mechanisms are in base of psychological dependence. It is similar to those that implement obsessive states (obsessive-compulsive disorders). The central role in these neurophysiological mechanisms is played by limbic system of the brain that provides emotional and motivational behavior of humans (and animals). It was shown that the treatment of medical-resistant forms of obsessive-compulsive disorders requires stereotactic impacts on various structures of the limbic system, including cingulate gyrus. According to literature data, there was several hundred stereotactic effects on the cingulate gyrus in the world. About 1000 stereotactic operations have been performed in our country as a mental addiction of heroin dependent patients' treatment. The efficiency was of about 70%.

Remote neural regulation mediated by nanomaterials

Neural regulation techniques play an essential role in the functional dissection of neural circuits and also the treatment of neurological diseases. Recently, a series of nanomaterials, including upconversion nanoparticles (UCNPs), magnetic nanoparticles (MNPs), and silicon nanomaterials (SNMs) that are responsive to remote optical or magnetic stimulation, have been applied as transducers to facilitate localized control of neural activities. In this review, we summarize the latest advances in nanomaterial-mediated neural regulation, especially in a remote and minimally invasive manner. We first give an overview of existing neural stimulation techniques, including electrical stimulation, transcranial magnetic stimulation, chemogenetics, and optogenetics, with an emphasis on their current limitations. Then we focus on recent developments in nanomaterial-mediated neural regulation, including UCNP-mediated fiberless optogenetics, MNP-mediated magnetic neural regulation, and SNM-mediated non-genetic neural regulation. Finally, we discuss the possibilities and challenges for nanomaterial-mediated neural regulation.

International Regulatory Standards for the Qualitative Measurement of Deep Brain Stimulation in Clinical Research

Deep brain stimulation (DBS) has progressed to become a promising treatment modality for neurologic and psychiatric disorders like epilepsy and major depressive disorder due to its growing personalization. Despite evidence pointing to the benefits of DBS if tested on these personalized qualitative metrics, rather than randomized-control trial quantitative standards, the evaluation of these novel devices appears to be based on the latter. This study surveyed the presence of this trend in the national regulatory guidelines of the prominent DBS researching countries. It was found that two governing bodies, in the European Union and Australia, acknowledged the option for qualitative measures. These findings support further development of national regulatory guidelines, so the neuroscientific community developing these neurotechnologies can better understand the impact their treatments have on patients.

Past, Present, and Future of Deep Brain Stimulation: Hardware, Software, Imaging, Physiology and Novel Approaches

Deep brain stimulation (DBS) has advanced treatment options for a variety of neurologic and neuropsychiatric conditions. As the technology for DBS continues to progress, treatment efficacy will continue to improve and disease indications will expand. Hardware advances such as longer-lasting batteries will reduce the frequency of battery replacement and segmented leads will facilitate improvements in the effectiveness of stimulation and have the potential to minimize stimulation side effects. Targeting advances such as specialized imaging sequences and “connectomics” will facilitate improved accuracy for lead positioning and trajectory planning. Software advances such as closed-loop stimulation and remote programming will enable DBS to be a more personalized and accessible technology. The future of DBS continues to be promising and holds the potential to further improve quality of life. In this review we will address the past, present and future of DBS.

Achieving long-term stability of thin-film electrodes for neurostimulation

Implantable electrodes that can reliably measure brain activity and deliver an electrical stimulus to a target tissue are increasingly employed to treat various neurological diseases and neuropsychiatric disorders. Flexible thin-film electrodes have gained attention over the past few years to minimise invasiveness and damage upon implantation. Research has previously focused on optimising the electrode's electrical and mechanical properties; however, their chronic stability must be validated to translate electrodes from a research to a clinical application. Neurostimulation electrodes, which actively inject charge, have yet to reliably demonstrate continuous functionality for ten years or more in vivo, the accepted metric for clinical viability. Long-term stability can only be achieved if the focus switches to investigating how and why such devices fail. Unfortunately, there is a field-wide reluctance to investigate device stability and failures, which hinders device optimisation. This review surveys thin-film electrode designs with a focus on adhesion between electrode layers and the interactions with the surrounding environment. A comprehensive summary of the abiotic failure modes faced by such electrodes is presented, and to encourage investigation, systematic methods for analysing their origin are recommended. Finally, approaches to reducing the likelihood of device failure are offered. STATEMENT OF SIGNIFICANCE: Neural electrodes that can deliver an electrical stimulus to a target tissue are widely used to treat various neurological diseases. Essential to the function of these electrodes is the ability to safely stimulate the target tissue for extended periods (> 10 years); however, this has not yet been clinically achieved. The key to achieving long-term stability is an increased understanding of electrode interactions with the surrounding tissue and subsequent systematic analysis of their failure modes. This review highlights the need for a change in the approach to investigating electrode failure, and in doing so summarizes the common ways in which neural electrodes fail, methods for identifying them and approaches to preventing them.

Deep Brain Stimulation for Intractable Obsessive-Compulsive Disorder and Treatment-Resistant Depression

In deep brain stimulation (DBS), a neurostimulation device is implanted to generate electrical fields in targeted deep brain regions in order to affect circuits associated with neuropsychiatric illness for potential therapeutic benefit. The development of DBS has followed a decades-long history of psychiatric neurosurgery, with advances in pacemakers and spinal neurostimulation devices allowing for the use of DBS in the treatment of neuropsychiatric disorders. Currently, deep brain stimulation for psychiatric illness has been approved by the U.S. Food and Drug Administration for the treatment of intractable obsessive-compulsive disorder, through a Humanitarian Device Exemption. The use of DBS for treatment-resistant depression is another promising application of this technology. Several potential targets of DBS have shown promise for treating neuropsychiatric illness, but few have demonstrated efficacy in randomized controlled trials. Future directions for DBS research will likely include modified trial designs, refined targets, the use of tractography for more specific and individualized targeting, and development of closed-loop DBS.

Critical Factors and Economic Methods for Regulatory Impact Assessment in the Medical Device Industry

Introduction

Methods

Results

Discussion

Toward personalized medicine in connectomic deep brain stimulation

At the group-level, deep brain stimulation leads to significant therapeutic benefit in a multitude of neurological and neuropsychiatric disorders. At the single-patient level, however, symptoms may sometimes persist despite "optimal" electrode placement at established treatment coordinates. This may be partly explained by limitations of disease-centric strategies that are unable to account for heterogeneous phenotypes and comorbidities observed in clinical practice. Instead, tailoring electrode placement and programming to individual patients' symptom profiles may increase the fraction of top-responding patients. Here, we propose a three-step, circuit-based framework with the aim of developing patient-specific treatment targets that address the unique symptom constellation prevalent in each patient. First, we describe how a symptom network target library could be established by mapping beneficial or undesirable DBS effects to distinct circuits based on (retrospective) group-level data. Second, we suggest ways of matching the resulting symptom networks to circuits defined in the individual patient (template matching). Third, we introduce network blending as a strategy to calculate optimal stimulation targets and parameters by selecting and weighting a set of symptom-specific networks based on the symptom profile and subjective priorities of the individual patient. We integrate the approach with published literature and conclude by discussing limitations and future challenges.

Trading Vulnerabilities: Living with Parkinson's Disease before and after Deep Brain Stimulation

Implanted medical devices-for example, cardiac defibrillators, deep brain stimulators, and insulin pumps-offer users the possibility of regaining some control over an increasingly unruly body, the opportunity to become part "cyborg" in service of addressing pressing health needs. We recognize the value and effectiveness of such devices, but call attention to what may be less clear to potential users-that their vulnerabilities may not entirely disappear but instead shift. We explore the kinds of shifting vulnerabilities experienced by people with Parkinson's disease (PD) who receive therapeutic deep brain stimulators to help control their tremors and other symptoms of PD.

Powering Implantable and Ingestible Electronics

Implantable and ingestible biomedical electronic devices can be useful tools for detecting physiological and pathophysiological signals, and providing treatments that cannot be done externally. However, one major challenge in the development of these devices is the limited lifetime of their power sources. The state-of-the-art of powering technologies for implantable and ingestible electronics is reviewed here. The structure and power requirements of implantable and ingestible biomedical electronics are described to guide the development of powering technologies. These powering technologies include novel batteries that can be used as both power sources and for energy storage, devices that can harvest energy from the human body, and devices that can receive and operate with energy transferred from exogenous sources. Furthermore, potential sources of mechanical, chemical, and electromagnetic energy present around common target locations of implantable and ingestible electronics are thoroughly analyzed; energy harvesting and transfer methods befitting each energy source are also discussed. Developing power sources that are safe, compact, and have high volumetric energy densities is essential for realizing long-term in-body biomedical electronics and for enabling a new era of personalized healthcare.

A narrative review on invasive brain stimulation for treatment-resistant depression

While most patients with depression respond to pharmacotherapy and psychotherapy, about one-third will present treatment resistance to these interventions. For patients with treatment-resistant depression (TRD), invasive neurostimulation therapies such as vagus nerve stimulation, deep brain stimulation, and epidural cortical stimulation may be considered. We performed a narrative review of the published literature to identify papers discussing clinical studies with invasive neurostimulation therapies for TRD. After a database search and title and abstract screening, relevant English-language articles were analyzed. Vagus nerve stimulation, approved by the U.S. Food and Drug Administration as a TRD treatment, may take several months to show therapeutic benefits, and the average response rate varies from 15.2-83%. Deep brain stimulation studies have shown encouraging results, including rapid response rates (> 30%), despite conflicting findings from randomized controlled trials. Several brain regions, such as the subcallosal-cingulate gyrus, nucleus accumbens, ventral capsule/ventral striatum, anterior limb of the internal capsule, medial-forebrain bundle, lateral habenula, inferior-thalamic peduncle, and the bed-nucleus of the stria terminalis have been identified as key targets for TRD management. Epidural cortical stimulation, an invasive intervention with few reported cases, showed positive results (40-60% response), although more extensive trials are needed to confirm its potential in patients with TRD.

A Systematic Review of Neuromodulation Treatment Effects on Suicidality

Introduction: Neuromodulation is an important group of therapeutic modalities for neuropsychiatric disorders. Prior studies have focused on efficacy and adverse events associated with neuromodulation. Less is known regarding the influence of neuromodulation treatments on suicidality. This systematic review sought to examine the effects of various neuromodulation techniques on suicidality. Methods: A systematic review of the literature from 1940 to 2020 following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline was conducted. Any reported suicide-related outcome, including suicidal ideation, suicide intent, suicide attempt, completed suicide in reports were considered as a putative measure of treatment effect on suicidality. Results: The review identified 129 relevant studies. An exploratory analysis of a randomized controlled trial comparing the effects of sertraline and transcranial direct-current stimulation (tDCS) for treating depression reported a decrease in suicidal ideation favoring tDCS vs. placebo and tDCS combined with sertraline vs. placebo. Several studies reported an association between repetitive transcranial magnetic stimulation and improvements in suicidal ideation. In 12 of the studies, suicidality was the primary outcome, ten of which showed a significant improvement in suicidal ideation. Electroconvulsive therapy (ECT) and magnetic seizure therapy was also shown to be associated with lower suicidal ideation and completed suicide rates. There were 11 studies which suicidality was the primary outcome and seven of these showed an improvement in suicidal ideation or suicide intent and fewer suicide attempts or completed suicides in patients treated with ECT. There was limited literature focused on the potential protective effect of vagal nerve stimulation with respect to suicidal ideation. Data were mixed regarding the potential effects of deep brain stimulation on suicidality. Conclusions: Future prospective studies of neuromodulation that focus on the primary outcome of suicidality are urgently needed. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=125599, identifier: CRD42019125599.

Deep Brain Stimulation for Tremor and Dystonia

Deep brain stimulation (DBS) is the most commonly used surgical treatment for drug-refractory movement disorders such as tremor and dystonia. Appropriate patient selection along with target selection is important to ensure optimal outcome without complications. This review summarizes the recent literature regarding the mechanism of action, indications, outcome, and complications of DBS in tremor and dystonia. A comparison with other modalities of surgical interventions is discussed along with a note of the recent advances in technology. Future research needs to be directed to understand the underlying etiopathogenesis of the disease and the way in which DBS modulates the intracranial abnormal networks.

Complications associated with deep brain stimulation for Parkinson's disease: a MAUDE study

INTRODUCTION

Deep brain stimulation (DBS) is a common surgical option for the treatment of medically refractory Parkinson's disease (PD). Manufacturer and User Facility Device Experience (MAUDE), a United States Food and Drug Administration (FDA)-compiled database of adverse event reports related to medical devices, is a public resource that can provide insight into the relative frequency of complications and patient complaints.

MATERIALS AND METHODS

We accessed the MAUDE database and queried for adverse reports for deep brain stimulators implanted for PD from January 1, 2009 to December 31, 2018. Complaints were classified into device malfunction, patient non-compliance, patient complaint, surgically managed complications (i.e. complications that are corrected via surgery), and death. Patient complaints were further stratified into ineffective stimulation, shock, overstimulation, battery-related problems, or pain at the pulse generator site. Surgically managed complications were classified as intraoperative complications, impedance, migration, erosion, infection, lead fracture, and lead disconnection. Each event could receive multiple classifications and subclassifications.

RESULTS

A total of 4,189 adverse event reports was obtained. These encompassed 2,805 patient complaints. Within this group, 797 (28%) events were classified as ineffective stimulation. There were 1,382 surgically managed complications, 104 (8%) of which were intraoperative complications, 757 (55%) documented impedance issues, 381 (28%) infections, and 413 (30%) lead-related issues. There were 53 documented deaths.

CONCLUSIONS

The MAUDE database has potential use as a real time monitor for elucidating the relative occurrence of complications associated with deep brain stimulation. It also allows for the analysis of device-related complications in specific patient populations. Although the database is useful in this endeavor, it requires improvements particularly in the standardization of reporting adverse events.

Hydrogel facilitated bioelectronic integration

The recent advances in bio-integratable electronics are creating new opportunities for investigating and directing biologically significant processes, yet their performance to date is still limited by the inherent physiochemical and signaling mismatches at the heterogeneous interfaces. Hydrogels represent a unique category of materials to bridge the gap between biological and electronic systems because of their structural/functional similarity to biological tissues and design versatility to accommodate cross-system communication. In this review, we discuss the latest progress in the engineering of hydrogel interfaces for bioelectronics development that promotes (1) structural compatibility, where the mechanical and chemical properties of hydrogels can be modulated to achieve coherent, chronically stable biotic-abiotic junctions; and (2) interfacial signal transduction, where the charge and mass transport within the hydrogel mediators can be rationally programmed to condition/amplify the bioderived signals and enhance the electrical/electrochemical coupling. We will further discuss the application of functional hydrogels in complex physiological environments for bioelectronic integration across different scales/biological levels. These ongoing research efforts have the potential to blur the distinction between living systems and artificial electronics, and ultimately decode and regulate biological functioning for both fundamental inquiries and biomedical applications.

Deep brain stimulation for psychiatric disorders: From focal brain targets to cognitive networks

Deep brain stimulation (DBS) is a promising intervention for treatment-resistant psychiatric disorders, particularly major depressive disorder (MDD) and obsessive-compulsive disorder (OCD). Up to 90% of patients who have not recovered with therapy or medication have reported benefit from DBS in open-label studies. Response rates in randomized controlled trials (RCTs), however, have been much lower. This has been argued to arise from surgical variability between sites, and recent psychiatric DBS research has focused on refining targeting through personalized imaging. Much less attention has been given to the fact that psychiatric disorders arise from dysfunction in distributed brain networks, and that DBS likely acts by altering communication within those networks. This is in part because psychiatric DBS research relies on subjective rating scales that make it difficult to identify network biomarkers. Here, we overview recent DBS RCT results in OCD and MDD, as well as the follow-on imaging studies. We present evidence for a new approach to studying DBS' mechanisms of action, focused on measuring objective cognitive/emotional deficits that underpin these and many other mental disorders. Further, we suggest that a focus on cognition could lead to reliable network biomarkers at an electrophysiologic level, especially those related to inter-regional synchrony of the local field potential (LFP). Developing the network neuroscience of DBS has the potential to finally unlock the potential of this highly specific therapy.