Optimal Stimulation Parameters Research Articles

Epidural Spinal Cord Stimulation Acutely Modulates Lower Urinary Tract and Bowel Function Following Spinal Cord Injury: A Case Report.

Regaining control of autonomic functions such as those of the cardiovascular system, lower urinary tract and bowel, rank among the most important health priorities for individuals living with spinal cord injury (SCI). Recently our research provided evidence that epidural spinal cord stimulation (ESCS) could acutely modulate autonomic circuits responsible for cardiovascular function after SCI. This finding raised the question of whether ESCS can be used to modulate autonomic circuits involved in lower urinary tract and bowel control after SCI. We present the case of a 32-year-old man with a chronic motor-complete SCI (American Spinal injury Association Impairment Scale B) at the 5th cervical spinal segment. He sustained his injury during a diving accident in 2012. He was suffering from neurogenic lower urinary tract and bowel dysfunction. Epidural stimulation of the lumbosacral spinal cord immediately modulated both functions without negatively affecting the cardiovascular system. Specifically, the individual’s bowel function was assessed using different pre-set configurations and stimulation parameters in a randomized order. Compared to the individual’s conventional bowel management approach, ESCS significantly reduced the time needed for bowel management (p = 0.039). Furthermore, depending on electrode configuration and stimulation parameters (i.e., amplitude, frequency, and pulse width), ESCS modulated detrusor pressure and external anal sphincter/pelvic floor muscle tone to various degrees during urodynamic investigation. Although, ESCS is currently being explored primarily for restoring ambulation, our data suggest that application of this neuroprosthetic intervention may provide benefit to lower urinary tract and bowel function in individuals with SCI. To fully capitalize on the potential of improving lower urinary tract and bowel function, further research is needed to better understand the neuronal pathways and identify optimal stimulation configurations and parameters.

Bayesian adaptive dual control of deep brain stimulation in a computational model of Parkinson's disease.

In this paper, we present a novel Bayesian adaptive dual controller (ADC) for autonomously programming deep brain stimulation devices. We evaluated the Bayesian ADC’s performance in the context of reducing beta power in a computational model of Parkinson’s disease, in which it was tasked with finding the set of stimulation parameters which optimally reduced beta power as fast as possible. Here, the Bayesian ADC has dual goals: (a) to minimize beta power by exploiting the best parameters found so far, and (b) to explore the space to find better parameters, thus allowing for better control in the future. The Bayesian ADC is composed of two parts: an inner parameterized feedback stimulator and an outer parameter adjustment loop. The inner loop operates on a short time scale, delivering stimulus based upon the phase and power of the beta oscillation. The outer loop operates on a long time scale, observing the effects of the stimulation parameters and using Bayesian optimization to intelligently select new parameters to minimize the beta power. We show that the Bayesian ADC can efficiently optimize stimulation parameters, and is superior to other optimization algorithms. The Bayesian ADC provides a robust and general framework for tuning stimulation parameters, can be adapted to use any feedback signal, and is applicable across diseases and stimulator designs.

Measurements of Temporal Summation of Heat Pain: a Pilot Investigation in Healthy Humans

Temporal summation of pain (TSP) is a promising tool for measuring the pain modulation processes in healthy subjects and patients with chronic pain. We tried to find optimal stimulation parameters in order to elicit a robust reproducible TSP phenomenon. Twenty healthy volunteers (15 women and 5 men) completed four sessions/conditions of pulsating heat pain stimulation, applied to the left forearm with a frequency of 0.33–0.4 sec–1 using a contact heat-evoked potential stimulator. The stimulation temperature (step +0.5°C or +1.0°C up to the pain threshold, pain tolerance), pulse duration (500, 800, or 1000 msec), and number of stimuli (60 or 90) were varied. The participants rated the pain intensity at the first and every 10th heat pulse, using a numeric rating scale (NRS) 0–100. The TSP was calculated as the difference between the lowest rating and the rating of the last stimulus and was compared between conditions. The optimal condition (19 out of 20 participants responded with TSP) showed temperature at pain tolerance, pulse duration of 800 msec, and 90 stimuli. In addition, this condition showed weaker side effects (painful discomfort) than those with less (60) but longer (1000 msec) stimuli presented 1.0 degree above the pain threshold. The protocol with a relatively high stimulus repetition and a moderate pulse duration seems to be the optimal protocol to reproduce TSP. Heat stimulation with longer pulse durations and higher stimulation temperatures was less feasible.

Regulation of C2C12 Differentiation and Control of the Beating Dynamics of Contractile Cells for a Muscle-Driven Biosyncretic Crawler by Electrical Stimulation

Biosyncretic robots have potential advantages associated with both living organisms and electromechanical systems. Skeletal muscle tissue is a candidate as bioactuators for biosyncretic robots because of its excellent contraction force and controllability. However, the low quality of myoblast (C2C12) differentiation into contractile myotubes and the lack of control research on biosyncretic robots are two of the main challenges in the development of biosyncretic robots. In this study, an approach with circularly distributed multiple electrodes (CEs) is proposed to improve C2C12 differentiation and to control the movement of a myotube-based biosyncretic crawling robot. To analyze the advantages of the proposed CEs, the electrical characteristics of CEs and a pair of traditional parallel stimulation electrodes (PEs) were simulated and compared with each other. Then, to determine the optimal electrical stimulation parameters and demonstrate the superiorities of the proposed CEs, electrical pulses with different parameters were used to stimulate two-dimensional and three-dimensional cells during culture with the proposed CEs and PEs. After this the control characteristics of the muscle tissue by the CEs were investigated from the relevance of pulse width-threshold voltage, voltage-contractility, frequency-contractility, and electric field direction-contractility by measuring the real-time responses of myotubes to different electrical stimulations. Moreover, to demonstrate the control of biosyncretic robots by the CEs, a biomimetic biosyncretic crawler actuated by myotubes was designed, fabricated, and controlled to move at different speeds by varying directions of electric field. This study not only provides a potential tool for the development and control of biosyncretic robots but is also informative for muscle tissue engineering and cardiomyocyte culture.

Attenuation of hypertension by C-fiber stimulation of the human median nerve and the concept-based novel device

High blood pressure (BP) is a highly controllable risk factor for cardiovascular diseases; however, awareness of this condition and the rates of controlled hypertension are low. Experimental animal studies have shown that stimulation of the median nerve or PC6 acupoint over the wrist has effects on cardiovascular activities, including reductions in systolic and diastolic BPs. A proof-of-concept study was conducted in humans to investigate whether stimulation of median nerve near PC6 acupoint decreased high BP, identify the optimal stimulation parameters for the BP-lowering effects of median nerve stimulation, and determine the specific peripheral nerves or types of afferent fibers mediating the BP-lowering effects. Median nerve stimulation was carried out bilaterally or unilaterally with different stimulation parameters, and the BP and heart rate were monitored. The afferent mechanisms underlying the effects of median nerve stimulation on hypertension were investigated via microneurography, A-fiber blocking experiments, and localized chemical or electrical stimulation. Bilateral median nerve stimulation at either low or high frequencies produced profound but transient reductions in systolic BP, which were elicited when median nerve stimulation was unilaterally applied at interelectrode distances of 2 and 4 cm. Systolic BP was also reduced by electrical stimulation of the thumb on the palm side. Although microneurographic recordings revealed the excitation of both A- and C-fibers following median nerve stimulation, the median nerve-mediated reductions in BP were not affected by A-fiber blockade, and they were mimicked by the activation of C-fibers with capsaicin. The present results indicate that activation of C-fibers in the median nerve generates BP-lowering effects in humans. Based on our clinical study, an optimized median nerve stimulator was built and combined with a wrist BP monitor for simultaneous BP measurements and median nerve stimulation.

Differential effects of high-definition transcranial direct current stimulation on verbal working memory performance according to sensory modality

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that modulates cortical excitability in a polarity-dependent manner. The diffuse nature of tDCS makes it difficult to investigate the optimal stimulation parameters for more effective and specific cognitive enhancement; to address this deficit, a more focalized stimulation technique, high-definition tDCS (HD-tDCS), has been developed. To date, only a few studies have examined the effects of HD-tDCS on cognitive functions; and none has investigated the effects of HD-tDCS on different sensory modalities of verbal working memory. Therefore, the present study compared the effects of prefrontal HD-tDCS on visual and auditory working memory tasks. Twenty healthy participants completed three sessions of each modality task, and additionally a sustained attention task. Anodal or sham HD-tDCS was administered to the dorsolateral prefrontal cortex (DLPFC) during the second session of the task in a parallel, single-blind design. Anodal stimulation to the DLPFC significantly enhanced the visual verbal working memory accuracy during and 20 min after the stimulation. In contrast, auditory verbal working memory performance was not modulated by anodal stimulation. Anodal stimulation to the DLPFC showed no effect on any other cognitive functions. The present study revealed the differential effects of HD-tDCS on two different modalities (visual vs. auditory) of working memory performance: important preliminary findings for the establishment of a more effective and specific use of tDCS.

EEG-triggered TMS reveals stronger brain state-dependent modulation of motor evoked potentials at weaker stimulation intensities

BackgroundCorticospinal excitability depends on the current brain state. The recent development of real-time EEG-triggered transcranial magnetic stimulation (EEG-TMS) allows studying this relationship in a causal fashion. Specifically, it has been shown that corticospinal excitability is higher during the scalp surface negative EEG peak compared to the positive peak of μ-oscillations in sensorimotor cortex, as indexed by larger motor evoked potentials (MEPs) for fixed stimulation intensity. ObjectiveWe further characterize the effect of μ-rhythm phase on the MEP input-output (IO) curve by measuring the degree of excitability modulation across a range of stimulation intensities. We furthermore seek to optimize stimulation parameters to enable discrimination of functionally relevant EEG-defined brain states. MethodsA real-time EEG-TMS system was used to trigger MEPs during instantaneous brain-states corresponding to μ-rhythm surface positive and negative peaks with five different stimulation intensities covering an individually calibrated MEP IO curve in 15 healthy participants. ResultsMEP amplitude is modulated by μ-phase across a wide range of stimulation intensities, with larger MEPs at the surface negative peak. The largest relative MEP-modulation was observed for weak intensities, the largest absolute MEP-modulation for intermediate intensities. These results indicate a leftward shift of the MEP IO curve during the μ-rhythm negative peak. ConclusionThe choice of stimulation intensity influences the observed degree of corticospinal excitability modulation by μ-phase. Lower stimulation intensities enable more efficient differentiation of EEG μ-phase-defined brain states.

Periodic flashing coordinated reset stimulation paradigm reduces sensitivity to ON and OFF period durations.

Pathological synchronization in the basal ganglia network has been considered an important component of Parkinson’s disease pathophysiology. An established treatment for some patients with Parkinson’s disease is deep brain stimulation, in which a tonic high-frequency pulse train is delivered to target regions of the brain. In recent years, a novel neuromodulation paradigm called coordinated reset stimulation has been proposed, which aims to reverse the pathological synchrony by sequentially delivering short high-frequency bursts to distinct sub-regions of the pathologically synchronized network, with an average intra-burst interval for each sub-region corresponding to period of the pathological oscillation. It has further been proposed that the resultant desynchronization can be enhanced when stimulation is interrupted periodically, and that it is particularly beneficial to precisely tune the stimulation ON and OFF time-windows to the underlying pathological frequency. Pre-clinical and clinical studies of coordinated reset stimulation have relied on these proposals for their stimulation protocols. In this study, we present a modified ON-OFF coordinated reset stimulation paradigm called periodic flashing and study its behavior through computational modeling using the Kuramoto coupled phase oscillator model. We demonstrate that in contrast to conventional coordinated reset stimulation, the periodic flashing variation does not exhibit a need for precise turning of the ON-OFF periods to the pathological frequency, and demonstrates desynchronization for a wide range of ON and OFF periods. We provide a mechanistic explanation for the previously observed sensitivities and demonstrate that they are an artifact of the specific ON-OFF cycling paradigm used. As a practical consequence, the periodic flashing paradigm simplifies the tuning of optimal stimulation parameters by decreasing the dimension of the search space. It also suggests new, more flexible ways of delivering coordinated reset stimulation.

Comparison of tractography‐assisted to atlas‐based targeting for deep brain stimulation in essential tremor

Direct targeting of the dentato-rubro-thalamic tract is efficacious in DBS for tremor suppression. We sought to compare outcomes and optimal stimulation parameters for tremor control using the technique of directly targeting the dentato-rubro-thalamic tract to those who underwent indirect targeting of the ventral intermediate nucleus thalamus. Twenty consecutive essential tremor patients obtained preoperative diffusion MRIs, where the dentato-rubro-thalamic tract was individually drawn and used to directly target the ventral intermediate nucleus of the thalamus during surgery. These patients were compared to an earlier cohort of 20 consecutive patients who underwent surgery using atlas-based coordinates. Baseline and 1-year postsurgery tremor amplitude using The Essential Tremor Rating Assessment Scale was recorded, as were the parameters needed for successful tremor control. The indirectly targeted group had greater baseline and postop tremor severity relative to those directly targeted (baseline, 2.9 vs. 2.6; P = 0.02; postop, 1.1 vs. 0.8; P = 0.03). Mean voltage, pulse width, and frequency for optimal tremor control in the directly targeted group (38 electrodes) = 2.8 V, 80 μs, 153 Hz; the parameters for the indirectly targeted group (38 electrodes) = 2.9 V, 86 µs, 179 Hz (significantly greater, P < 0.001). Both groups had significant improvement in arm tremor amplitude from baseline (P < 0.001) without sustained side effects. Direct targeting of the dentato-rubro-thalamic tract provides excellent tremor control, comparable to indirectly targeting the ventral intermediate nucleus of the thalamus. Use of lower stimulation parameters, especially frequency, to control tremor in the directly targeted group suggests that it is a more efficient targeting methodology, which may minimize battery depletion. © 2018 International Parkinson and Movement Disorder Society.

Is Euthanasia Psychiatric Treatment? The Struggle With Death on Request in the Netherlands.

A 42-year-old married woman with three children was referred to our department for treatment of treatment-resistant depression. Pharmacotherapy, psychotherapy, and ECT were unsuccessful. We applied deep brain stimulation, which was partially effective and reduced depressive symptoms by 30%, but the patient still suffered. During our struggle to find optimal deep brain stimulation parameters in the course of treatment, the patient requested that her general physician provide euthanasia. Following guidelines in the Netherlands, our team was consulted, but we disapproved because her suffering was not prospectless and there still were treatment options with deep brain stimulation. Although we had treated her intensively for 2 years, our advice was disregarded. Eight weeks later we received the obituary of the patient.

Vagus nerve stimulation as a tool for enhancing extinction in exposure-based therapies.

Emotionally traumatic experiences can lead to maladaptive memories that are enduring and intrusive. The goal of exposure-based therapies is to extinguish conditioned fears through repeated, unreinforced exposures to reminders of traumatic events. The extinction of conditioned fear depends upon the consolidation of new memories made during exposure to reminders. An impairment in extinction recall, observed in certain patient populations, can interfere with progress in exposure-based therapies, and the drive to avoid thoughts and reminders of the trauma can undermine compliance and increase dropout rate. Effective adjuncts to exposure-based therapies should improve the consolidation and maintenance of the extinction memory or improve the tolerability of the therapy. Under stressful conditions, the vagus nerve responds to elevations in epinephrine and signals the brain to facilitate the storage of new memories while, as part of the parasympathetic nervous system, it slows the sympathetic response. Here, we review studies relevant to fear extinction, describing the anatomical and functional characteristics of the vagus nerve and mechanisms of vagus nerve stimulation (VNS)-induced memory enhancement and plasticity. We propose that stimulation of the left cervical vagus nerve during exposure to conditioned cues signals the brain to store new memories just as epinephrine or emotional arousal would do, but bypasses the peripheral sympathetic "fight-or-flight" response. In support of this hypothesis, we have found that VNS accelerates extinction and prevents reinstatement of conditioned fear in rats. Finally, we propose future studies targeting the optimization of stimulation parameters and the search for biomarkers of VNS effectiveness that may improve exposure therapy outcomes.

Deep brain stimulation for dementias.

OBJECTIVE The aim of this article is to review the authors' and published experience with deep brain stimulation (DBS) therapy for the treatment of patients with Alzheimer's disease (AD) and Parkinson's disease dementia (PDD). METHODS Two targets are current topics of investigation in the treatment of AD and PDD, the fornix and the nucleus basalis of Meynert. The authors reviewed the current published clinical experience with attention to patient selection, biological rationale of therapy, anatomical targeting, and clinical results and adverse events. RESULTS A total of 7 clinical studies treating 57 AD patients and 7 PDD patients have been reported. Serious adverse events were reported in 6 (9%) patients; none resulted in death or disability. Most studies were case reports or Phase 1/2 investigations and were not designed to assess treatment efficacy. Isolated patient experiences demonstrating improved clinical response after DBS have been reported, but no significant or consistent cognitive benefits associated with DBS treatment could be identified across larger patient populations. CONCLUSIONS PDD and AD are complex clinical entities, with investigation of DBS intervention still in an early phase. Recently published studies demonstrate acceptable surgical safety. For future studies to have adequate power to detect meaningful clinical changes, further refinement is needed in patient selection, metrics of clinical response, and optimal stimulation parameters.

Therapeutic potential of deep brain stimulation of the nucleus accumbens in morbid obesity.

OBJECTIVE Morbid obesity is a growing problem worldwide. The current treatment options have limitations regarding effectiveness and complication rates. New treatment modalities are therefore warranted. One of the options is deep brain stimulation (DBS) of the nucleus accumbens (NAC). This review aims to summarize the current knowledge on NAC-DBS for the treatment of morbid obesity. METHODS Studies were obtained from multiple electronic bibliographic databases, supplemented with searches of reference lists. All animal and human studies reporting on the effects of NAC-DBS on body weight in morbidly obese patients were included. Articles found during the search were screened by 2 reviewers, and when deemed applicable, the relevant data were extracted. RESULTS Five relevant animal experimental papers were identified, pointing toward a beneficial effect of high-frequency stimulation of the lateral shell of the NAC. Three human case reports show a beneficial effect of NAC-DBS on body weight in morbidly obese patients. CONCLUSIONS The available literature supports NAC-DBS to treat morbid obesity. The number of well-conducted animal studies, however, is very limited. Also, the optimal anatomical position of the DBS electrode within the NAC, as well as the optimal stimulation parameters, has not yet been established. These matters need to be addressed before this strategy can be considered for human clinical trials.

Non-invasive brain stimulation in chronic orofacial pain: a systematic review.

BackgroundTranscranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) are non-invasive brain stimulation techniques that are being explored as therapeutic alternatives for the management of various chronic pain conditions.ObjectiveThe primary objective of this systematic review is to assess the efficacy of TMS and tDCS in reducing clinical pain intensity in chronic orofacial pain (OFP) disorders. The secondary objectives are to describe adverse effects, duration of relief, and TMS/tDCS methodologies used in chronic OFP disorders.MethodsA search was performed in MEDLINE, Embase, Web of Science, Scopus, and Google Scholar. Inclusion criteria were 1) population: adults diagnosed with chronic OFP including neuropathic and non-neuropathic disorders; 2) intervention: active TMS or tDCS stimulation regardless of the used protocol; 3) comparison: sham TMS or tDCS stimulation; and 4) outcome: primary outcome was patient reported pain intensity. Secondary outcomes were duration of pain relief, adverse effects, and methodological parameters. Risk of bias and quality of study reporting were also assessed.ResultsA total of 556 individual citations were identified by the search strategy, with 14 articles meeting selection criteria (TMS=11; tDCS=3). Data were obtained for a total of 228 patients. Included OFP disorders were trigeminal neuralgia, trigeminal neuropathy, burning mouth syndrome, atypical facial pain, and temporomandibular disorders. Significant pain reductions were obtained in both techniques. More number of sessions yielded to more durable effects. Overall, high risk of bias and poor study quality were found.ConclusionTMS and tDCS appear to be safe and promising alternatives to reduce pain intensity in different chronic OFP disorders. Additional research effort is needed to reduce bias, improve quality, and characterize optimal brain stimulation parameters to promote their efficacy.

Attenuation of cocaine seeking in rats via enhancement of infralimbic cortical activity using stable step-function opsins.

The infralimbic cortex (IL) and its downstream projection target the nucleus accumbens shell (NAshell) mediate the active suppression of cocaine-seeking behavior. Although an optogenetic approach would be beneficial for stimulating the IL and its efferents to study their role during reinstatement of cocaine seeking, the use of channelrhodopsin introduces significant difficulties, as optimal stimulation parameters are not known. The present experiments utilized a stable step-function opsin (SSFO) to potentiate endogenous activity in the IL and in IL terminals in the NAshell during cocaine-seeking tests to determine how these manipulations affect cocaine-seeking behaviors. Rats first underwent 6-h access cocaine self-administration followed by 21-27days in the homecage. Rats then underwent cue-induced and cocaine-primed drug-seeking tests during which the optogenetic manipulation was given. The same rats then underwent extinction training, followed by cue-induced and cocaine-primed reinstatements. Potentiation of endogenous IL activity did not significantly alter cue-induced or cocaine-primed drug seeking following the homecage period. However, following extinction training, enhancement of endogenous IL activity attenuated cue-induced reinstatement by 35% and cocaine-primed reinstatement by 53%. Stimulation of IL terminals in the NAshell did not consistently alter cocaine-seeking behavior. These results suggest the utility of an SSFO-based approach for enhancing activity in a structure without driving specific patterns of neuronal firing. However, the utility of an SSFO-based approach for axon terminal stimulation remains unclear. Moreover, these results suggest that the ability of the IL to reduce cocaine seeking depends, at least in part, on rats first having undergone extinction training.

Dosing of Electrical Parameters in Deep Brain Stimulation (DBS) for Intractable Depression: A Review of Clinical Studies.

Background: The electrical parameters used for deep brain stimulation (DBS) in movement disorders have been relatively well studied, however for the newer indications of DBS for psychiatric indications these are less clear. Based on the movement disorder literature, use of the correct stimulation parameters should be crucial for clinical outcomes. This review examines the stimulation parameters used in DBS studies for treatment resistant depression (TRD) and their relevance to clinical outcome and brain targets.Methods: We examined the published studies on DBS for TRD archived in major databases. Data on stimulus parameters (frequency, pulse width, amplitude), stimulation mode, brain target, efficacy, safety, and duration of follow up were extracted from 29 observational studies including case reports of patients with treatment resistant unipolar, bipolar, and co-morbid depression.Results: The algorithms commonly used to optimize efficacy were increasing amplitude followed by changing the electric contacts or increasing pulse width. High frequency stimulation (>100 Hz) was applied in most cases across brain targets. Keeping the high frequency stimulation constant, three different combinations of parameters were mainly used: (i) short pulse width (60–90 us) and low amplitude (0–4 V), (ii) short pulse width and high amplitude (5–10 V), (iii) long pulse width (120–450 us) and low amplitude. There were individual variations in clinical response to electrical dosing and also in the time of clinical recovery. There was no significant difference in mean stimulation parameters between responders and non-responders suggesting a role for stimulation unrelated factors in response.Conclusions: Although limited by open trials and small sample size, three optimal stimulation parameter combinations emerged from this review. Studies are needed to assess the comparative efficacy and safety of these combinations, such as a registry of data from patients undergoing DBS for TRD with individual data on stimulation parameters.

Mathematical Modeling for Description of Oscillation Suppression Induced by Deep Brain Stimulation.

A mathematical modeling for description of oscillation suppression by deep brain stimulation (DBS) is explored in this paper. High-frequency DBS introduced to the basal ganglia network can suppress pathological neural oscillations that occur in the Parkinsonian state. However, selecting appropriate stimulation parameters remains a challenging issue due to the limited understanding of the underlying mechanisms of the Parkinsonian state and its control. In this paper, we use a describing function analysis to provide an intuitive way to select the optimal stimulation parameters based on a biologically plausible computational model of the Parkinsonian neural network. By the stability analysis using the describing function method, effective DBS parameter regions for inhibiting the pathological oscillations can be predicted. Additionally, it is also found that a novel sinusoidal-shaped DBS may become an alternative stimulation pattern and expends less energy, but with a different mechanism. This paper provides new insight into the possible mechanisms underlying DBS and a prediction of optimal DBS parameter settings, and even suggests how to select novel DBS wave patterns for the treatment of movement disorders, such as Parkinson's disease.

Design and assessment of stimulation parameters for a novel peripheral nerve interface.

Bi-directional interfaces for peripheral nerve stimulation and recording aim to improve control and acceptance of sensorized prosthetic limbs. The implantable multimodal peripheral recording and stimulation system (IMPRESS) is an intraneural interface technology supporting a high-density transverse intrafascicular multichannel electrode (hd-TIME). Herein we report on in vivo selectivity studies using a passive hd-TIME, and computational modeling towards optimal stimulation parameters for fiber recruitment.

Bioheat transfer model of transcutaneous spinal cord stimulation-induced temperature changes.

Transcutaneous spinal cord stimulation (tSCS) has been extensively studied due to its promising application in motor function restoration. Many previous studies have explored both the essential mechanism of action and the methods for determining optimal stimulation parameters. In contrast, the bioheat transfer analysis of tSCS therapy has not been investigated to the same extent, despite widely existing, and being of great significance in assuring a stable and thermally safe treatment. In this paper, we concentrated on the thermal effects of tSCS using a finite element-based method. By coupling the electric field and bioheat field, systematic finite element simulations were performed on a human spinal cord model to survey the influence of anatomical structures, blood perfusion, and stimulation parameters on temperature changes for the first time. The results show that tSCS-induced temperature rise mainly occurs in the skin and fat layers and varies due to individual differences. The current density distribution along with the interactions of multiple biothermal effects synthetically determines the thermal status of the whole spinal cord model. Smaller stimulation electrodes have a higher risk of thermal damage when compared with larger electrodes. Increasing the stimulation intensity will result in more joule heat accumulation, hence an increase in the temperature. Among all configurations in this study that simulated the clinical tSCS protocols, the temperature rise could reach up to 9.4 °C on the skin surface depending on the stimulation parameters and tissue blood perfusion.

Can deep transcranial magnetic stimulation (DTMS) be used to treat substance use disorders (SUD)? A systematic review

BackgroundDeep transcranial magnetic stimulation (DTMS) is a non-invasive method of stimulating widespread cortical areas and, presumably, deeper neural networks. The current study assessed the effects of DTMS in the treatment of substance use disorders (SUD) using a systematic review.MethodsElectronic literature search (PsycInfo, Medline until April 2017) identified k = 9 studies (k = 4 randomized-controlled trials, RCTs, with inactive sham and k = 5 open-label studies). DTMS was most commonly applied using high frequency/intensity (10–20 Hz/100–120% of the resting motor threshold, MT) protocols for 10–20 daily sessions in cases with alcohol, nicotine or cocaine use disorders. The outcome measures were craving and dependence (according to standardized scales) or consumption (frequency, abstinence or results of biological assays) at the end of the daily treatment phases and at the last follow-up.ResultsAcute and longer-term (6–12 months) reductions in alcohol craving were observed after 20 sessions (20 Hz, 120% MT) relative to baseline in k = 4 open-label studies with comorbid SUD and major depressive disorder (MDD). In k = 2 RCTs without MDD, alcohol consumption acutely decreased after 10–12 sessions (10–20 Hz, 100–120% MT) relative to baseline or to sham. Alcohol craving was reduced only after higher frequency/intensity DTMS (20 Hz, 120% MT) relative to sham in k = 1 RCT. Nicotine consumption was reduced and abstinence was increased after 13 sessions (10 Hz, 120% MT) and at the 6-month follow-up relative to sham in k = 1 RCT. Cocaine craving was reduced after 12 sessions (15 Hz, 100% MT) and at the 2-month follow-up relative to baseline in k = 1 open-label study while consumption was reduced after 12 sessions (10 Hz, 100% MT) relative to baseline but not to sham in k = 1 RCT.ConclusionsHigh-frequency DTMS may be effective at treating some SUD both acutely and in the longer-term. Large RCTs with inactive sham are required to determine the efficacy and the optimal stimulation parameters of DTMS for the treatment of SUD.