Deep brain stimulation in movement and psychiatric disorders

Role of deep brain stimulation (DBS) in addiction disorders

Background

Addiction disorders pose significant challenges to public health, necessitating innovative treatments. This assesses deep brain stimulation (DBS) as a potential intervention for addiction disorders.

Methods

A literature review was carried out with a focus on the role of DBS in addiction disorders and its future implications in neurosurgical research.

Results

The online literature shows that DBS precisely modulates certain brain regions to restore addiction-related neural circuits and promote behavioral control.

Conclusion

Preclinical evidence demonstrates DBS's potential to rebalance neural circuits associated with addiction, and early clinical trials provide encouraging outcomes in enhancing addiction-related outcomes. Ethical considerations, long-term safety, and personalized patient selection require further investigation.

Efficacy and Safety of Electroconvulsive Therapy in Patients With Deep Brain Stimulation: Literature Review, Case Report for Patient With Essential Tremor, and Practical Recommendations

AIM

Deep brain stimulation (DBS) has proven to be an effective therapy of some treatment-resistant psychiatric disorders and movement disorders. Comorbid depressive symptoms are common and difficult to manage. Treatment with electroconvulsive therapy (ECT) may be required. There are few published cases describing the safety and efficacy of ECT for patients with DBS implants, and there are no available guidelines for administration of ECT in patients with DBS and mood disorders. The current study had 3 aims: (i) to conduct a systematic review of case reports on patients with DBS implants who received ECT; (ii) to report the case of a 69-year-old man with a DBS implant for essential tremor, who required ECT; and (iii) to provide practical recommendations for ECT in patients with DBS implants.

METHODS

We conducted a systematic review, in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, of existing case reports on patients with DBS implants administered ECT for psychiatric disorders.

RESULTS

Our search yielded 25 cases of ECT in patients implanted with DBS systems. In addition, we here describe successful ECT management of major depressive disorder in a patient treated by DBS. We also set forth ECT management guidelines based on points of consensus. The 2 most important practical recommendations are to make sure the DBS system is set to 0 V and turned off before ECT, and to avoid sites near the DBS electrodes.

CONCLUSIONS

Electroconvulsive therapy may be an effective and safe treatment for DBS patients with MDD.

Where do we stand now regarding treatment of psychiatric and neurodegenerative disorders? Considerations in using magnetoelectric nanoparticles as an innovative approach

Almost 1000 million people have recently been diagnosed with a mental health or substance disorder (Ritchie & Roser, 2018). Psychiatric disorders, and their treatment, represent a big burden to the society worldwide, causing about 8 million deaths per year (Walker et al., 2015). Daily progress in science enables continuous advances in methods to treat patients; however, the brain remains to be the most unknown and complex organ of the body. There is a growing demand for innovative approaches to treat psychiatric as well as neurodegenerative disorders, disorders with unknown curability, and treatments mostly designed to slow disease progression. Based on that need and the peculiarity of the central nervous system, in the present review, we highlight the handicaps of the existing approaches as well as discuss the potential of the recently introduced magnetoelectric nanoparticles (MENPs) to become a game-changing tool in future applications for the treatment of brain alterations. Unlike other stimulation approaches, MENPs have the potential to enable a wirelessly controlled stimulation at a single-neuron level without requiring genetic modification of the neural tissue and no toxicity has yet been reported. Their potential as a new tool for targeting the brain is discussed. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Cardiovascular Disease Therapeutic Approaches and Drug Discovery > Neurological Disease.

Hypothalamic deep brain stimulation as a strategy to manage anxiety disorders

SignificanceAnxiety disorders are among the most prevalent mental illnesses worldwide. Despite significant advances in their treatment, many patients remain treatment resistant. Thus, new treatment modalities and targets are much needed. Therefore, we developed a deep brain stimulation therapy that targets a recently identified anxiety center in the lateral hypothalamus. We show that this therapy rapidly silences anxiety-implicated neurons and immediately relieves diverse anxiety symptoms in a variety of stressful situations. This therapeutic effect occurs without acute or chronic side effects that are typical of many existing treatments, such as physical sedation or memory deficits. These findings identify a clinically applicable new therapeutic strategy for helping patients to manage treatment-resistant anxiety.

Methodological Considerations for Setting Up Deep Brain Stimulation Studies for New Indications

Deep brain stimulation (DBS) is a neurosurgical treatment with a growing range of indications. The number of clinical studies is expanding because of DBS for new indications and efforts to improve DBS for existing indications. To date, various methods have been used to perform DBS studies. Designing a clinical intervention study with active implantable medical devices has specific challenges while expanding patient treatment. This paper provides an overview of the key aspects that are essential for setting up a DBS study.

Deep brain stimulation and electromagnetic interference

Deep brain stimulation (DBS) has evolved into an approved and efficacious treatment for movement, obsessive-compulsive, and epilepsy disorders that are refractory to medical therapy, with current investigation into other disease conditions. However, there are unintentional and intentional sources of external electromagnetic interference (EMI) that can lead to either malfunctioning or damaged DBS devices, as well as injury to human tissue. Comprehensive studies and guidelines on such topics in the medical literature are scarce. Herein, we review the principles behind EMI, as well as the various potential sources of interference, both unintentional (e.g. stray EMI fields) and intentional (e.g. MRI scans, "brainjacking"). Additionally, we employ the Manufacturer and User Device Facility Experience (MAUDE) database to assess real-world instances of EMI (e.g., airport body scanners, magnetic resonance imaging (MRI), and electrosurgery) affecting DBS devices commonly implanted in the United States (US).

Picosecond Pulse Electrical Field Suppressing Spike Firing in Hippocampal CA1 in Rat In Vivo

Picosecond pulse electrical fields (psPEFs), due to their high temporal-resolution accuracy and localization, were viewed as a potential targeted and noninvasive method for neuromodulation. However, few studies have reported psPEFs regulating neuronal activity in vivo. In this paper, a preliminary study on psPEFs regulating action potentials in hippocampus CA1 of rats in vivo was carried out. By analyzing the neuronal spike firing rate in hippocampus CA1 pre- and post-psPEF stimulation, effects of frequency, duration, and dosimetry of psPEFs were studied. The psPEF used in this study had a pulse width of 500 ps and a field strength of 1 kV/mm, established by 1 kV picosecond voltage pulses. Results showed that the psPEF suppressed spike firing in hippocampal CA1 neurons. The suppression effect was found to be significant except for 10 s, 10 Hz. For short-duration stimulation (10 s), the inhibition rate of spike firing increased with frequency. At longer stimulation durations (1 and 2 min), the inhibition rate increased and decreased alternately as the frequency increased. Despite this, the inhibition rate at high frequencies (5 and 10 kHz) was significantly larger than that at 10 and 100 Hz. A cumulative effect of psPEF on spike firing inhibition was found at low frequencies (10 and 100 Hz), which was saturated when frequency reached 500 Hz or higher. This paper conducts a study on psPEF regulating spike firing in hippocampal CA1 in vivo for the first time and guides subsequent study on psPEF achieving noninvasive neuromodulation. © 2020 Bioelectromagnetics Society.

Transcranial magnetic stimulation, deep brain stimulation, and other forms of neuromodulation for substance use disorders: Review of modalities and implications for treatment

Given the high prevalence of individuals diagnosed with substance use disorder, along with the elevated rate of relapse following treatment initiation, investigating novel approaches and new modalities for substance use disorder treatment is of vital importance. One such approach involves neuromodulation which has been used therapeutically for neurological and psychiatric disorders and has demonstrated positive preliminary findings for the treatment of substance use disorder. The following article provides a review of several forms of neuromodulation which warrant consideration as potential treatments for substance use disorder. PubMed, PsycINFO, Ovid MEDLINE, and Web of Science were used to identify published articles and clinicaltrials.gov was used to identify currently ongoing or planned studies. Search criteria for Brain Stimulation included the following terminology: transcranial direct current stimulation, transcranial magnetic stimulation, theta burst stimulation, deep brain stimulation, vagus nerve stimulation, trigeminal nerve stimulation, percutaneous nerve field stimulation, auricular nerve stimulation, and low intensity focused ultrasound. Search criteria for Addiction included the following terminology: addiction, substance use disorder, substance-related disorder, cocaine, methamphetamine, amphetamine, alcohol, nicotine, tobacco, smoking, marijuana, cannabis, heroin, opiates, opioids, and hallucinogens. Results revealed that there are currently several forms of neuromodulation, both invasive and non-invasive, which are being investigated for the treatment of substance use disorder. Preliminary findings have demonstrated the potential of these various neuromodulation techniques in improving substance treatment outcomes by reducing those risk factors (e.g. substance craving) associated with relapse. Specifically, transcranial magnetic stimulation has shown the most promise with several well-designed studies supporting the potential for reducing substance craving. Deep brain stimulation has also shown promise, though lacks well-controlled clinical trials to support its efficacy. Transcranial direct current stimulation has also demonstrated promising results though consistently designed, randomized trials are also needed. There are several other forms of neuromodulation which have not yet been investigated clinically but warrant further investigation given their mechanisms and potential efficacy based on findings from other studied indications. In summary, given promising findings in reducing substance use and craving, neuromodulation may provide a non-pharmacological option as a potential treatment and/or treatment augmentation for substance use disorder. Further research investigating neuromodulation, both alone and in combination with already established substance use disorder treatment (e.g. medication treatment), warrants consideration.

Systematic Evaluation of DBS Parameters in the Hemi-Parkinsonian Rat Model

Electrical stimulation of the subthalamic nucleus (STN) is clinically employed to ameliorate several symptoms of manifest Parkinson’s Disease (PD). Stimulation parameters utilized by chronically implanted pulse generators comprise biphasic rectangular short (60–100 μs) pulses with a repetition frequency between 130 and 180 Hz. A better insight into the effect of electrical stimulation parameters could potentially reveal new possibilities for the improvement of deep brain stimulation (DBS) as a treatment. To this end, we employed single-sided 6-hydroxidopamine (6-OHDA) lesioning of the medial forebrain bundle (MFB) in rats to systematically investigate alternative stimulation parameters. These hemi-parkinsonian (hemi-PD) rats underwent individualized, ipsilateral electrical stimulation to the STN of the lesioned hemisphere, while the transiently induced contralateral rotational behavior was quantified to assess the effect of DBS parameter variations. The number of induced rotations during 30 s of stimulation was strongly correlated with the amplitude of the stimulation pulses. Despite a general linear relation between DBS frequency and rotational characteristics, a plateau effect was observed in the rotation count throughout the clinically used frequency range. Alternative waveforms to the conventional biphasic rectangular (Rect) pulse shapes [Triangular (Tri), Sinusoidal (Sine), and Sawtooth (Lin.Dec.)] required higher charges per phase to display similar behavior in rats as compared to the conventional pulse shape. The Euclidean Distance (ED) was used to quantify similarities between different angular trajectories. Overall, our study confirmed that the effect of different amplitude and frequency parameters of STN-DBS in the hemi-PD rat model was similar to those in human PD patients. This shows that induced contralateral rotation is a valuable readout in testing stimulation parameters. Our study supports the call for more pre-clinical studies using this measurement to assess the effect of other DBS parameters such as pulse-width and interphase intervals.

Entrainment of a network of interacting neurons with minimum stimulating charge

Periodic pulse train stimulation is generically used to study the function of the nervous system and to counteract disease-related neuronal activity, e.g., collective periodic neuronal oscillations. The efficient control of neuronal dynamics without compromising brain tissue is key to research and clinical purposes. We here adapt the minimum charge control theory, recently developed for a single neuron, to a network of interacting neurons exhibiting collective periodic oscillations. We present a general expression for the optimal waveform, which provides an entrainment of a neural network to the stimulation frequency with a minimum absolute value of the stimulating current. As in the case of a single neuron, the optimal waveform is of bang-off-bang type, but its parameters are now determined by the parameters of the effective phase response curve of the entire network, rather than of a single neuron. The theoretical results are confirmed by three specific examples: two small-scale networks of FitzHugh-Nagumo neurons with synaptic and electric couplings, as well as a large-scale network of synaptically coupled quadratic integrate-and-fire neurons.

Modular Current Stimulation System for Pre-clinical Studies

Electric stimulators with precise and reliable outputs are an indispensable part of electrophysiological research. From single cells to deep brain or neuromuscular tissue, there are diverse targets for electrical stimulation. Even though commercial systems are available, we state the need for a low-cost, high precision, functional, and modular (hardware, firmware, and software) current stimulation system with the capacity to generate stable and complex waveforms for pre-clinical research. The system presented in this study is a USB controlled 4-channel modular current stimulator that can be expanded and generate biphasic arbitrary waveforms with 16-bit resolution, high temporal precision (μs), and passive charge balancing: the NES STiM (Neuro Electronic Systems Stimulator). We present a detailed description of the system's structural design, the controlling software, reliability test, and the pre-clinical studies [deep brain stimulation (DBS) in hemi-PD rat model] in which it was utilized. The NES STiM has been tested with MacOS and Windows operating systems. Interfaces to MATLAB source codes are provided. The system is inexpensive, relatively easy to build and can be assembled quickly. We hope that the NES STiM will be used in a wide variety of neurological applications such as Functional Electrical Stimulation (FES), DBS and closed loop neurophysiological research.

A pilot study of bed nucleus of the stria terminalis deep brain stimulation in treatment-resistant depression

BACKGROUND

Studies are increasingly investigating the therapeutic effects of deep brain stimulation (DBS) applied to a variety of brain regions in the treatment of patients with highly treatment refractory depression. Limited research to date has investigated the therapeutic potential of DBS applied to the Bed Nucleus Of Stria Terminalis (BNST).

OBJECTIVE

The aim of this study was to explore the therapeutic potential of DBS applied to the BNST.

METHOD

Five patients with highly treatment resistant depression underwent DBS to the BNST in an open label case series design.

RESULTS

BNST DBS resulted in sustained remission of depression in two of the five patients, provided substantial therapeutic improvement two further patients, and had minimal antidepressant effect for the final patient. There were no operative complications and stimulation related side effects were limited and reversible with adjustment of stimulation. However, the time to achieve and complexity of programming required to achieve optimal therapeutic outcomes varied substantially between patients.

CONCLUSION

DBS applied to the BNST as therapeutic potential in patients with highly refractory depression and warrants exploration in larger clinical studies.

Advanced research on deep brain stimulation in treating mental disorders

Deep brain stimulation is a method that involves using an electric stimulus on a specific target in the brain with stereotaxis. It is a minimally invasive, safe, adjustable and reversible nerve involvement technology. At present, this technique is widely applied to treat movement disorders and has produced promising effects on mental symptoms, including combined anxiety and depression. Deep brain stimulation has therefore been employed as a novel treatment for depression, obsessive-compulsive disorder, habituation, Tourette's syndrome, presenile dementia, anorexia nervosa and other refractory mental illnesses. Many encouraging results have been reported. The aim of the present review was to briefly describe the mechanisms, target selection, side effects, ethical arguments and risks associated with deep brain stimulation. Although deep brain stimulation is a developing and promising treatment, a large amount of research is still required to determine its curative effect, and the selection of patients and targets must be subjected to strict ethical standards.

The future of psychiatry: brain devices

Recent advances in deep brain stimulators and brain-machine interfaces have greatly expanded the possibilities of neuroprosthetics and neuromodulation. Together with advances in neuroengineering, nanotechnology, molecular biology and material sciences, it is now possible to address fundamental questions in neuroscience in new, more powerful ways. It is now possible to apply these new technologies in ways that range from augmenting and restoring function to neuromodulation modalities that treat neuropsychiatric disorders. Recent developments in neuromodulation methods offer significant advantages and potential clinical benefits for a variety of disorders. Here we describe the current state of the art in neuromodulation methods, and some advances in brain-machine interfaces, describing the advantages and limitations of the clinical applications of each method. The future applications of these new methods and how they will shape the future of psychiatry and medicine, along with safety and ethical implications, are also discussed.

An implantable device for neuropsychiatric rehabilitation by chronic deep brain stimulation in freely moving rats

Successful practice of clinical deep brain stimulation (DBS) calls for basic research on the mechanisms and explorations of new indications in animals. In the article, a new implantable, single-channel, low-power miniature device is proposed, which may transmit pulses chronically into the brain nucleus of freely moving rats. The DBS system consists of an implantable pulse generator (IPG), a bipolar electrode, and an external programmer. The IPG circuit module is assembled as a 20-mm diameter circular board and fixed on a rat’s skull together with an electrode and battery. The rigid electrode may make its fabrication and implantation more easy. The external programmer is designed for bidirectional communication with the IPG by a telecontrol transceiver and adjusts stimulation parameters. A biological validation was performed in which the effects of electrical stimulation in brain nucleus accumbens were detected. The programmed parameters were accurate, implant steady, and power sufficient to allow stimulation for more than 3 months. The larger area of the electrode tip provided a moderate current or charge density and minimized the damage from electrochemistry and pyroelectricity. The rats implanted with the device showed a reduction in morphine-induced conditioned place preference after high-frequency stimulation. In conclusion, the DBS device is based on the criteria of simple technology, minimal invasion, low cost, small in size, light-weight, and wireless controlled. This shows that our DBS device is appropriate and can be used for preclinical studies, indicating its potential utility in the therapy and rehabilitation of neuropsychiatric disorders.

A comparative historical and demographic study of the neuromodulation management techniques of deep brain stimulation for dystonia and cochlear implantation for sensorineural deafness in children

Cochlear implants for sensorineural deafness in children is one of the most successful neuromodulation techniques known to relieve early chronic neurodisability, improving activity and participation. In 2012 there were 324,000 recipients of cochlear implants globally.

AIM

To compare cochlear implant (CI) neuromodulation with deep brain stimulation (DBS) for dystonia in childhood and explore relations between age and duration of symptoms at implantation and outcome.

METHODS

Comparison of published annual UK CI figures for 1985-2009 with a retrospective cohort of the first 9 years of DBS for dystonia in children at a single-site Functional Neurosurgery unit from 2006 to 14.

RESULTS

From 2006 to 14, DBS neuromodulation of childhood dystonia increased by a factor of 3.8 to a total of 126 cases over the first 9 years, similar to the growth in cochlear implants which increased by a factor of 4.1 over a similar period in the 1980s rising to 527 children in 2009. The CI saw a dramatic shift in practice from implantation at >5 years of age at the start of the programme towards earlier implantation by the mid-1990s. Best language results were seen for implantation <5 years of age and duration of cochlear neuromodulation >4 years, hence implantation <1 year of age, indicating that severely deaf, pre-lingual children could benefit from cochlear neuromodulation if implanted early. Similar to initial CI use, the majority of children receiving DBS for dystonia in the first 9 years were 5-15 years of age, when the proportion of life lived with dystonia exceeds 90% thus limiting benefits.

CONCLUSION

Early DBS neuromodulation for acquired motor disorders should be explored to maximise the benefits of dystonia reduction in a period of maximal developmental plasticity before the onset of disability. Learning from cochlear implantation, DBS can become an accepted management option in children under the age of 5 years who have a reduced proportion of life lived with dystonia, and not viewed as a last resort reserved for only the most severe cases where benefits may be at their most limited.

Brain Stimulation in Addiction

Localized stimulation of the human brain to treat neuropsychiatric disorders has been in place for over 20 years. Although these methods have been used to a greater extent for mood and movement disorders, recent work has explored brain stimulation methods as potential treatments for addiction. The rationale behind stimulation therapy in addiction involves reestablishing normal brain function in target regions in an effort to dampen addictive behaviors. In this review, we present the rationale and studies investigating brain stimulation in addiction, including transcranial magnetic stimulation, transcranial direct current stimulation, and deep brain stimulation. Overall, these studies indicate that brain stimulation has an acute effect on craving for drugs and alcohol, but few studies have investigated the effect of brain stimulation on actual drug and alcohol use or relapse. Stimulation therapies may achieve their effect through direct or indirect modulation of brain regions involved in addiction, either acutely or through plastic changes in neuronal transmission. Although these mechanisms are not well understood, further identification of the underlying neurobiology of addiction and rigorous evaluation of brain stimulation methods has the potential for unlocking an effective, long-term treatment of addiction.

Deep Brain Stimulation of Medial Dorsal and Ventral Anterior Nucleus of the Thalamus in OCD: A Retrospective Case Series

BACKGROUND

The current notion that cortico-striato-thalamo-cortical circuits are involved in the pathophysiology of obsessive-compulsive disorder (OCD) has instigated the search for the most suitable target for deep brain stimulation (DBS). However, despite extensive research, uncertainty about the ideal target remains with many structures being underexplored. The aim of this report is to address a new target for DBS, the medial dorsal (MD) and the ventral anterior (VA) nucleus of the thalamus, which has thus far received little attention in the treatment of OCD.

METHODS

In this retrospective trial, four patients (three female, one male) aged 31-48 years, suffering from therapy-refractory OCD underwent high-frequency DBS of the MD and VA. In two patients (de novo group) the thalamus was chosen as a primary target for DBS, whereas in two patients (rescue DBS group) lead implantation was performed in a rescue DBS attempt following unsuccessful primary stimulation.

RESULTS

Continuous thalamic stimulation yielded no significant improvement in OCD symptom severity. Over the course of thalamic DBS symptoms improved in only one patient who showed "partial response" on the Yale-Brown Obsessive Compulsive (Y-BOCS) Scale. Beck Depression Inventory scores dropped by around 46% in the de novo group; anxiety symptoms improved by up to 34%. In the de novo DBS group no effect of DBS on anxiety and mood was observable.

CONCLUSION

MD/VA-DBS yielded no adequate alleviation of therapy-refractory OCD, the overall strategy in targeting MD/VA as described in this paper can thus not be recommended in DBS for OCD. The magnocellular portion of MD (MDMC), however, might prove a promising target in the treatment of mood related and anxiety disorders.

Neuromodulation: present and emerging methods

Neuromodulation has wide ranging potential applications in replacing impaired neural function (prosthetics), as a novel form of medical treatment (therapy), and as a tool for investigating neurons and neural function (research). Voltage and current controlled electrical neural stimulation (ENS) are methods that have already been widely applied in both neuroscience and clinical practice for neuroprosthetics. However, there are numerous alternative methods of stimulating or inhibiting neurons. This paper reviews the state-of-the-art in ENS as well as alternative neuromodulation techniques-presenting the operational concepts, technical implementation and limitations-in order to inform system design choices.

Two-year outcomes of deep brain stimulation in adults with cerebral palsy

Objective

To investigate the effect of deep brain stimulation (DBS) on reducing dystonia and disability in adults with cerebral palsy (CP) and to compare the therapeutic outcomes between primary dystonia patients and CP patients over two years after bilateral pallidal DBS.

Methods

Five patients with primary dystonia and seven CP patients with dystonia were recruited. All subjects received DBS surgery in both globus pallidus. Burke-Fahn-Marsden dystonia rating scale consisting of dystonia movement score and disability score and subjective satisfaction scale were assessed after 1 month and every 6 months over two years following DBS treatment.

Results

On the dystonia movement scale, both groups of primary dystonia patients and CP patients showed a significant decrease over time following DBS. On the disability scale, patients with primary dystonia showed a significant decrease over time, whereas the disability score of CP patients did not change over the two years. Comparing the dystonia movement and disability scores of CP patients at each assessment, patients with primary dystonia showed a significant reduction after 6 months. Comparing the satisfaction scores of CP patients after DBS, patients with primary dystonia showed significantly higher subjective satisfaction.

Conclusion

Whereas dystonia can be significantly reduced in patients with primary dystonia, CP patients showed a modest improvement on the dystonia movement scale, but not on the disability scale. Therefore, DBS may be considered with caution as a treatment modality of CP patients with dystonia.

Development of Conductive Boron-Doped Diamond Electrode: A microscopic, Spectroscopic, and Voltammetric Study

Building on diamond characteristics such as hardness, chemical inertness and low electron emission threshold voltage, the current microscopic, spectroscopic and voltammetric investigations are directed towards improving the properties of electrode coating materials for their future use in clinical studies of deep brain stimulation via fast-scan cyclic voltammetry (FSCV). In this study we combine the capabilities of confocal Raman mapping in providing detailed and accurate analysis of local distributions of material constituents in a series of boron-doped polycrystalline diamond films grown by chemical vapor deposition, with information from the more conventional techniques of scanning electron microscopy (SEM) and infrared absorption spectroscopy. Although SEM images show a uniform distribution of film crystallites, they have the limitation of being unable to differentiate the distribution of boron in the diamond. Values of 10¹⁸–10²¹ atoms/cm³ of boron content have been estimated from the absorption coefficient of the 1290 cm⁻¹ infrared absorption band and from the 500 cm⁻¹ Raman vibration. The observed accumulation of boron atoms and carbon sp² impurities at the grain boundaries suggests that very high doping levels do not necessarily contribute to improvement of the material’s conductivity, corroborating with voltammetric data. FSCV results also indicate an enhanced stability of analyte detection.

Deep brain stimulation (DBS) at the interface of neurology and psychiatry

Deep brain stimulation (DBS) is an emerging interventional therapy for well-screened patients with specific treatment-resistant neuropsychiatric diseases. Some neuropsychiatric conditions, such as Parkinson disease, have available and reasonable guideline and efficacy data, while other conditions, such as major depressive disorder and Tourette syndrome, have more limited, but promising results. This review summarizes both the efficacy and the neuroanatomical targets for DBS in four common neuropsychiatric conditions: Parkinson disease, Tourette syndrome, major depressive disorder, and obsessive-compulsive disorder. Based on emerging new research, we summarize novel approaches to optimization of stimulation for each neuropsychiatric disease and we review the potential positive and negative effects that may be observed following DBS. Finally, we summarize the likely future innovations in the field of electrical neural-network modulation.

Pathways of translation: deep brain stimulation

Electrical stimulation of the brain has a 2000 year history. Deep brain stimulation (DBS), one form of neurostimulation, is a functional neurosurgical approach in which a high-frequency electrical current stimulates targeted brain structures for therapeutic benefit. It is an effective treatment for certain neuropathologic movement disorders and an emerging therapy for psychiatric conditions and epilepsy. Its translational journey did not follow the typical bench-to-bedside path, but rather reversed the process. The shift from ancient and medieval folkloric remedy to accepted medical practice began with independent discoveries about electricity during the 19th century and was fostered by technological advances of the 20th. In this paper, we review that journey and discuss how the quest to expand its applications and improve outcomes is taking DBS from the bedside back to the bench.

Dopamine measurement during prolonged deep brain stimulation: a proof-of-principle study of paired pulse voltammetry

PURPOSE

Deep Brain Stimulation (DBS) has been effective in treating various neurological and psychiatric disorders; however, its underlying mechanism hasn't been completely understood. Fast scan cyclic voltammetry (FSCV) is a valuable tool to elucidate underlying neurotransmitter mechanisms of DBS, due to its sub-second temporal resolution and direct identification of analytes. However, since DBS-like high frequency stimulation evokes neurotransmitter release as well as extracellular pH shift, it is hard to isolate the neurotransmitter signal from the complex environment. Here we demonstrate the efficacy of a modified FSCV technique, Paired Pulse Voltammetry (PPV), in detecting dopamine (DA) release in the caudate nucleus during long-term electrical stimulation of the medial forebrain bundle (MFB) in the rat.

METHODS

Unlike traditional FSCV applying a single triangular waveform, PPV employs a binary waveform with a specific time gap (2.2 ms) in between the comprising pulses. DA measurement was performed with a carbon fiber microelectrode placed in the caudate nucleus and a twisted bipolar stimulating electrode in the MFB. PPV data was collected with the Wireless Instantaneous Neurochemical Concentration Sensing System (WINCS).

RESULTS

Using PPV, the detection of DA was evident throughout the long-term stimulation (5 minutes); however, without PPV, in vivo environmental changes including pH shift eventually obscured the characteristic oxidation current of DA at 0.6V.

CONCLUSIONS

These results indicate that PPV can be a valuable tool to accurately determine DA dynamics in a complex in vivo environment during long-term electrical stimulation.

DBS of nucleus accumbens on heroin seeking behaviors in self-administering rats

BACKGROUND

Surgical ablation of select brain areas has been frequently used to alleviate psychological dependence on opiate drugs in certain countries. However, ablative brain surgery was stopped in China in 2004 due to the related ethical controversy and possible side effects. Deep brain stimulation (DBS), a less invasive, reversible and adjustable process of neuromodulation, was adopted to attenuate relapses in studies of drug addiction.

METHODS

Preclinical experiments were designed to assess the long-term effects of DBS of the nucleus accumbens (NAc) on cue- and heroin-induced reinstatement of drug seeking behaviors. After a rat self-administration model of heroin relapse was established, DBS was administered bilaterally or unilaterally to the NAc core through concentric bipolar electrodes. A 1-h long continuous stimulation (130 Hz, 100 μs, 0-150 μA) was given daily for 7 days during the abstinence session. Drug seeking behaviors were elicited by conditioned cues or a small dose of heroin.

RESULTS

75 μA and 150 μA bilateral NAc DBS attenuated cue- and heroin-induced reinstatement of drug seeking, and unilateral DBS of the right NAc achieved effects almost equivalent to bilateral DBS. Additional experiments showed that DBS had no long-term influence on locomotor activity and spatial learning and retention capabilities in Morris water maze tasks. Subsequent immunohistochemistry measurements revealed that the behavioral consequences were associated with a significant increase in the expression of pCREB and a reduction in the expression of ΔFosB in the NAc.

CONCLUSIONS

These findings indicate that the NAc DBS could be an effective and safe therapeutic option for preventing relapse to heroin addiction.

EFFICACY OF A NEW CHARGE-BALANCED BIPHASIC ELECTRICAL STIMULUS IN THE ISOLATED SCIATIC NERVE AND THE HIPPOCAMPAL SLICE

Most deep brain stimulators apply rectangular monophasic voltage pulses. By modifying the stimulus shape, it is possible to optimize stimulus efficacy and find the best compromise between clinical effect, minimal side effects and power consumption of the stimulus generator. In this study, we compared the efficacy of three types of charge-balanced biphasic pulses (CBBPs, nominal duration 100 μs) in isolated sciatic nerves and in in vitro hippocampal brain slices of the rat. Using these two models, we tested the efficacy of several stimulus shapes exclusively on axons (in the sciatic nerve) and compared the effect with that of stimuli in the more complex neuronal network of the hippocampal slice by considering the stimulus-response relation. We showed that (i) adding an interphase gap (IPG, range 100–500 μs) to the CBBP enhances stimulus efficacy in the rat sciatic nerve and (ii) that this type of stimuli (CBBP with IPG) is also more effective in hippocampal slices. This benefit was similar for both models of voltage and current stimulation. In our two models, asymmetric CBBPs were less beneficial. Therefore, CBBPs with IPG appear to be well suited for application to DBS, since they enhance efficacy, extend battery life and potentially reduce harmful side effects.

Neuromodulation therapies and treatment-resistant depression

Background

Patients with treatment-resistant depression (TRD) who showed partial response to pharmacological and psychotherapeutic interventions need a trial of neuromodulation therapies (NTs).

Objective

This paper aims to review evidence-based data on the use of NTs in TRD.

Method

Using keywords and combined-word strategy, multiple computer searches of PubMed, Google Scholar, Quertle(R), and Medline were conducted for retrieving relevant articles published in English-language peer-reviewed journals (2000–2012). Those papers that addressed NTs in TRD were retained for extensive review.

Results

Despite methodological challenges, a range of 30%–93% of TRD patients showed substantial improvement to one of the NTs. One hundred–percent improvement was reported in two single-case studies on deep brain stimulation. Some studies reported no benefits from transcranial direct current stimulation. NTs were reported to have good clinical efficacy, better safety margin, and benign side-effect profile. Data are limited regarding randomized clinical trials, long-term efficacy, and cost-effectiveness of these approaches. Both modified electroconvulsive therapy and magnetic seizure therapy were associated with reversible but disturbing neurocognitive adverse effects. Besides clinical utility, NTs including approaches on the horizon may unlock the biological basis underlying mood disorders including TRD.

Conclusion

NTs are promising in patients with TRD, as the majority of them show good clinical response measured by standardized depression scales. NTs need further technological refinements and optimization together with continuing well-designed studies that recruit larger numbers of participants with TRD.

The principle of coherence in multi-level brain information processing

Synchronisation has become one of the major scientific tools to explain biological order at many levels of organisation. In systems neuroscience, synchronised subthreshold and suprathreshold oscillatory neuronal activity within and between distributed neuronal assemblies is acknowledged as a fundamental mode of neuronal information processing. Coherent neuronal oscillations correlate with all basic cognitive functions, mediate local and long-range neuronal communication and affect synaptic plasticity. However, it remains unclear how the very fast and complex changes of functional neuronal connectivity necessary for cognition, as mediated by dynamic patterns of neuronal synchrony, could be explained exclusively based on the well-established synaptic mechanisms. A growing body of research indicates that the intraneuronal matrix, composed of cytoskeletal elements and their binding proteins, structurally and functionally connects the synapses within a neuron, modulates neurotransmission and memory consolidation, and is hypothesised to be involved in signal integration via electric signalling due to its charged surface. Theoretical modelling, as well as emerging experimental evidence indicate that neuronal cytoskeleton supports highly cooperative energy transport and information processing based on molecular coherence. We suggest that long-range coherent dynamics within the intra- and extracellular filamentous matrices could establish dynamic ordered states, capable of rapid modulations of functional neuronal connectivity via their interactions with neuronal membranes and synapses. Coherence may thus represent a common denominator of neurophysiological and biophysical approaches to brain information processing, operating at multiple levels of neuronal organisation, from which cognition may emerge as its cardinal manifestation.

The application of vagus nerve stimulation and deep brain stimulation in depression

Despite the progress in the pharmacotherapy of depression, there is a substantial proportion of treatment-resistant patients. Recently, reversible invasive stimulation methods, i.e. vagus nerve stimulation (VNS) and deep brain stimulation (DBS), have been introduced into the management of treatment-resistant depression (TRD). VNS has already received regulatory approval for TRD. This paper reviews the available clinical evidence and neurobiology of VNS and DBS in TRD. The principle of VNS is a stimulation of the left cervical vagus nerve with a programmable neurostimulator. VNS was examined in 4 clinical trials with 355 patients. VNS demonstrated steadily increasing improvement with full benefit after 6-12 months, sustained up to 2 years. Patients who responded best had a low-to-moderate antidepressant resistance. However, the primary results of the only controlled trial were negative. DBS involves stereotactical implantation of electrodes powered by a pulse generator into the specific brain regions. For depression, the targeted areas are the subthalamic nucleus, internal globus pallidus, ventral internal capsule/ventral striatum, the subgenual cingulated region, and the nucleus accumbens. Antidepressant effects of DBS were examined in case series with a total number of 50 TRD patients. Stimulation of different brain regions resulted in a reduction of depressive symptoms. The clinical data on the use of VNS and DBS in TRD are encouraging. The major contribution of the methods is a novel approach that allows for precise targeting of the specific brain areas, nuclei and circuits implicated in the etiopathogenesis of neuropsychiatric disorders. For clinical practice, it is necessary to identify patients who may best benefit from VNS or DBS.

Modulating affect, cognition, and behavior - prospects of deep brain stimulation for treatment-resistant psychiatric disorders

Most patients suffering from psychiatric disorders respond to combinations of psycho- and psychopharmacotherapy; however there are patients who profit little if anything even after many years of treatment. Since about a decade different modalities of targeted neuromodulation – among them most prominently – deep brain stimulation (DBS) – are being actively researched as putative approaches to very treatment-resistant forms of those disorders. Recently, promising pilot data have been reported both for major depression (MD) and obsessive–compulsive disorder (OCD). Given the fact that patients included in DBS studies had been treated unsuccessfully for many years with conventional treatment methods, renders these findings remarkable. Remarkable is the fact, that in case of the long-term studies underway for MD, patients show a stable response. This gives hope to a substantial percentage of therapy–resistant psychiatric patients requiring new therapy approaches. There are no fundamental ethic objections to its use in psychiatric disorders, but until substantial clinical data is available, mandatory standards are needed. DBS is a unique and very promising method for the treatment of therapy–resistant psychiatric patients. The method allows manipulating pathological neuronal networks in a very precise way.

Transcranial magnetic stimulation in the presence of deep brain stimulation implants: Induced electrode currents

The safety of transcranial magnetic stimulation (TMS) in patients with an implanted deep brain stimulation (DBS) systems has not been thoroughly investigated. One potential safety hazard is the induction of significant voltages in the subcutaneous leads in the scalp that could result in unintended electrical currents in the DBS electrode contacts. We measured ex-vivo the TMS-induced voltages and currents in DBS electrodes with the implantable pulse generator (IPG) set in various modes of operation. We show that voltages as high as 100 V resulting in currents as high as 83 mA can be induced in the DBS leads by a TMS pulse in all IPG modes. These currents are an order of magnitude higher than the normal DBS pulses, and could result in tissue damage. When the IPG is turned off, electrode currents flow only if the TMS-induced voltage exceeds 5 V.

Deep brain stimulation: technology at the cutting edge

Deep brain stimulation (DBS) surgery has been performed in over 75,000 people worldwide, and has been shown to be an effective treatment for Parkinson's disease, tremor, dystonia, epilepsy, depression, Tourette's syndrome, and obsessive compulsive disorder. We review current and emerging evidence for the role of DBS in the management of a range of neurological and psychiatric conditions, and discuss the technical and practical aspects of performing DBS surgery. In the future, evolution of DBS technology may depend on several key areas, including better scientific understanding of its underlying mechanism of action, advances in high-spatial resolution imaging and development of novel electrophysiological and neurotransmitter microsensor systems. Such developments could form the basis of an intelligent closed-loop DBS system with feedback-guided neuromodulation to optimize both electrode placement and therapeutic efficacy.

Evaluation of novel stimulus waveforms for deep brain stimulation

Deep brain stimulation (DBS) is an established therapy for the treatment of a wide range of neurological disorders. Historically, DBS and other neurostimulation technologies have relied on rectangular stimulation waveforms to impose their effects on the nervous system. Recent work has suggested that non-rectangular waveforms may have advantages over the traditional rectangular pulse. Therefore, we used detailed computer models to compare a range of charge-balanced biphasic waveforms with rectangular, exponential, triangular, Gaussian and sinusoidal stimulus pulse shapes. We explored the neural activation energy of these waveforms for both intracellular and extracellular current-controlled stimulation conditions. In the context of extracellular stimulation, we compared their effects on both axonal fibers of passage and projection neurons. Finally, we evaluated the impact of delivering the waveforms through a clinical DBS electrode, as opposed to a theoretical point source. Our results suggest that DBS with a 1 ms centered-triangular pulse can decrease energy consumption by 64% when compared with the standard 100 µs rectangular pulse (energy cost of 48 and 133 nJ, respectively, to stimulate 50% of a distributed population of axons) and can decrease energy consumption by 10% when compared with the most energy efficient rectangular pulse (1.25 ms duration). In turn, there may be measureable energy savings when using appropriately designed non-rectangular pulses in clinical DBS applications, thereby warranting further experimental investigation.

Deep brain stimulation of the nucleus accumbens shell increases impulsive behavior and tissue levels of dopamine and serotonin

The nucleus accumbens (NAc) is gaining interest as a target for deep brain stimulation (DBS) in refractory neuropsychiatric disorders with impulsivity as core symptom. The nucleus accumbens is composed of two subterritories, core and shell, which have different anatomical connections. In animal models, it has been shown that DBS of the NAc changes impulsive action. Here, we tested the hypothesis that a change in impulsive action by DBS of the NAc is associated with changes in dopamine levels. Rats received stimulating electrodes either in the NAc core or shell, and underwent behavioral testing in a reaction time task. In addition, in a second experiment, the effect of DBS of the NAc core and shell on extracellular dopamine and serotonin levels was assessed in the NAc and medial prefrontal cortex. Control subjects received sham surgery. We have found that DBS of the NAc shell stimulation induced more impulsive action but less perseverative checking. These effects were associated with increased levels of dopamine and serotonin in the NAc, but not in the medial prefrontal cortex. DBS of the NAc core had no effect on impulsive action, but decreased perseverative responses indicative of a better impulse control. In these subjects, no effects were found on neurotransmitter levels. Our data point out that DBS of the NAc shell has negative effects on impulsive action which is accompanied by increases of dopamine and serotonin levels in the NAc, whereas DBS of the NAc core has beneficial behavioral effects.

Evolving refractory major depressive disorder diagnostic and treatment paradigms: toward closed-loop therapeutics

Current antidepressant therapies do not effectively control or cure depressive symptoms. Pharmaceutical therapies altogether fail to address an estimated 4 million Americans who suffer from a recurrent and severe treatment-resistant form of depression known as refractory major depressive disorder. Subjective diagnostic schemes, differing manifestations of the disorder, and antidepressant treatments with limited theoretical bases each contribute to the general lack of therapeutic efficacy and differing levels of treatment resistance in the refractory population. Stimulation-based therapies, such as vagus nerve stimulation, transcranial magnetic stimulation, and deep brain stimulation, are promising treatment alternatives for this treatment-resistant subset of patients, but are plagued with inconsistent reports of efficacy and variable side effects. Many of these problems stem from the unknown mechanisms of depressive disorder pathogenesis, which prevents the development of treatments that target the specific underlying causes of the disorder. Other problems likely arise due to the non-specific stimulation of various limbic and paralimbic structures in an open-loop configuration. This review critically assesses current literature on depressive disorder diagnostic methodologies, treatment schemes, and pathogenesis in order to emphasize the need for more stringent depressive disorder classifications, quantifiable biological markers that are suitable for objective diagnoses, and alternative closed-loop treatment options tailored to well-defined forms of the disorder. A closed-loop neurostimulation device design framework is proposed, utilizing symptom-linked biomarker abnormalities as control points for initiating and terminating a corrective electrical stimulus which is autonomously optimized for correcting the magnitude and direction of observed biomarker abnormality.

Comonitoring of adenosine and dopamine using the Wireless Instantaneous Neurotransmitter Concentration System: proof of principle

OBJECT

The authors of previous studies have demonstrated that local adenosine efflux may contribute to the therapeutic mechanism of action of thalamic deep brain stimulation (DBS) for essential tremor. Real-time monitoring of the neurochemical output of DBS-targeted regions may thus advance functional neurosurgical procedures by identifying candidate neurotransmitters and neuromodulators involved in the physiological effects of DBS. This would in turn permit the development of a method of chemically guided placement of DBS electrodes in vivo. Designed in compliance with FDA-recognized standards for medical electrical device safety, the authors report on the utility of the Wireless Instantaneous Neurotransmitter Concentration System (WINCS) for real-time comonitoring of electrical stimulation-evoked adenosine and dopamine efflux in vivo, utilizing fast-scan cyclic voltammetry (FSCV) at a polyacrylonitrile-based (T-650) carbon fiber microelectrode (CFM).

METHODS

The WINCS was used for FSCV, which consisted of a triangle wave scanned between -0.4 and +1.5 V at a rate of 400 V/second and applied at 10 Hz. All voltages applied to the CFM were with respect to an Ag/AgCl reference electrode. The CFM was constructed by aspirating a single T-650 carbon fiber (r = 2.5 microm) into a glass capillary and pulling to a microscopic tip using a pipette puller. The exposed carbon fiber (the sensing region) extended beyond the glass insulation by approximately 50 microm. Proof of principle tests included in vitro measurements of adenosine and dopamine, as well as in vivo measurements in urethane-anesthetized rats by monitoring adenosine and dopamine efflux in the dorsomedial caudate putamen evoked by high-frequency electrical stimulation of the ventral tegmental area and substantia nigra.

RESULTS

The WINCS provided reliable, high-fidelity measurements of adenosine efflux. Peak oxidative currents appeared at +1.5 V and at +1.0 V for adenosine, separate from the peak oxidative current at +0.6 V for dopamine. The WINCS detected subsecond adenosine and dopamine efflux in the caudate putamen at an implanted CFM during high-frequency stimulation of the ventral tegmental area and substantia nigra. Both in vitro and in vivo testing demonstrated that WINCS can detect adenosine in the presence of other easily oxidizable neurochemicals such as dopamine comparable to the detection abilities of a conventional hardwired electrochemical system for FSCV.

CONCLUSIONS

Altogether, these results demonstrate that WINCS is well suited for wireless monitoring of high-frequency stimulation-evoked changes in brain extracellular concentrations of adenosine. Clinical applications of selective adenosine measurements may prove important to the future development of DBS technology.

From psychosurgery to neuromodulation: deep brain stimulation for intractable Tourette syndrome

Tourette syndrome is a neuropsychiatric disorder characterized by motor and vocal tics. It is often associated with depression, obsessive-compulsive symptoms, self-injurious behaviour and attention deficit-hyperactivity disorder (ADHD). In intractable patients, neuromodulation using deep brain stimulation (DBS) has widely replaced psychosurgery. Three different key structures are defined for DBS, the medial portion of the thalamus, the globus pallidus internus and the anterior limb of the internal capsule/nucleus accumbens. This is a comprehensive overview on the effect of DBS on motor and non-motor symptoms using different case series and two larger studies.

DBS-relevant electric fields increase hydraulic conductivity of in vitro endothelial monolayers

Deep brain stimulation (DBS) achieves therapeutic outcome through generation of electric fields (EF) in the vicinity of energized electrodes. Targeted brain regions are highly vascularized, and it remains unknown if DBS electric fields modulate blood-brain barrier (BBB) function, either through electroporation of individual endothelial cells or electro-permeation of barrier tight junctions. In our study, we calculated the intensities of EF generated around energized Medtronic 3387 and 3389 DBS leads by using a finite element model. Then we designed a novel stimulation system to study the effects of such fields with DBS-relevant waveforms and intensities on bovine aortic endothelial cell (BAEC) monolayers, which were used as a basic analog for the blood-brain barrier endothelium. Following 5 min of stimulation, we observed a transient increase in endothelial hydraulic conductivity (Lp) that could be related to the disruption of the tight junctions (TJ) between cells, as suggested by zonula occludens-1 (ZO-1) protein staining. This 'electro-permeation' occurred in the absence of cell death or single cell electroporation, as indicated by propidium iodide staining and cytosolic calcein uptake. Our in vitro results, using uniform fields and BAEC monolayers, thus suggest that electro-permeation of the BBB may occur at electric field intensities below those inducing electroporation and within intensities generated near DBS electrodes. Further studies are necessary to address potential BBB disruption during clinical studies, with safety and efficacy implications.