Frequency Electrical Stimulation Research Articles

Feedback Altitude Control of a Flying Insect–Computer Hybrid Robot

Unlike biomimetic methods, the insect–computer hybrid is an alternative approach to developing insect-scale robots. Insect–computer hybrid is a technique that transforms a living insect into a controllable robot by embedding it with artificial devices. In this article, a beetle ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Mecynorrhina torquata</i> ) was transformed into a hybrid flying system by mounting an electronic backpack and implanting electrodes on it. Wing trajectories during fictive flight climbing and flight diving were captured to investigate the natural flight-height control of beetles. Compare with the electrically induced wing trajectories via basalar, subalar, and third axillary (3Ax) muscle stimulations, we hypothesized that the basalar muscles are involved in ascending flight, whereas the 3Ax muscles function to reduce the flight-height. By reproducing the electrical stimulations on bilateral muscle pairs during free flights, we found that stimulations of the basalar muscle pair increased vertical accelerations. In contrast, the 3Ax muscle pair's stimulation decreased vertical accelerations gradually as a function of the electrical stimulation frequency. Accordingly, a proportional-derivative feedback controller was proposed to maintain the beetles' flight-height using frequency-dependent electrical pulses on the basalar and 3Ax muscles. In this article, the altitude control of a free-flying beetle was demonstrated for the first time.

Research on feature classification of lower limb motion imagination based on electrical stimulation to enhance rehabilitation

Motor imaging therapy is of great significance to the rehabilitation of patients with stroke or motor dysfunction, but there are few studies on lower limb motor imagination. When electrical stimulation is applied to the posterior tibial nerve of the ankle, the steady-state somatosensory evoked potentials (SSSEP) can be induced at the electrical stimulation frequency. In order to better realize the classification of lower extremity motor imagination, improve the classification effect, and enrich the instruction set of lower extremity motor imagination, this paper designs two experimental paradigms: Motor imaging (MI) paradigm and Hybrid paradigm. The Hybrid paradigm contains electrical stimulation assistance. Ten healthy college students were recruited to complete the unilateral movement imagination task of left and right foot in two paradigms. Through time-frequency analysis and classification accuracy analysis, it is found that compared with MI paradigm, Hybrid paradigm could get obvious SSSEP and ERD features. The average classification accuracy of subjects in the Hybrid paradigm was 78.61%, which was obviously higher than the MI paradigm. It proves that electrical stimulation has a positive role in promoting the classification training of lower limb motor imagination.

Influence of wide-pulse neuromuscular electrical stimulation frequency and superimposed tendon vibration on occurrence and magnitude of extra torque

Low-frequency and high-frequency wide-pulse neuromuscular electrical stimulation (NMES) can generate extra-torque (ET) via afferent pathways. Superimposing tendon vibration (TV) to NMES can increase the activation of these afferent pathways and favour ET generation. Knowledge of the characteristics of ET is essential to implement these stimulation paradigms in clinical practice. Thus, we aimed at investigating the effects of frequency and TV superimposition on the occurrence and magnitude of ET in response to wide-pulse NMES. NMES-induced isometric plantar flexion torque was recorded in 30 healthy individuals who performed five NMES protocols: wide-pulse low-frequency (1 ms; 20 Hz; WPLF) and wide-pulse high-frequency (1 ms; 100 Hz; WPHF) without and with superimposed TV (1 mm; 100 Hz) and conventional NMES (50 µs; 20 Hz; reference protocol). Each NMES protocol began with an adjustment of NMES intensity in order to reach 10% of maximal voluntary contraction then consisted of three 20-s trains interspersed by 90 s of rest. The ET occurrence was similar for WPLF and WPHF (p=0.822). In the responders, the ET magnitude was greater for WPHF than WPLF (p<0.001). There was no effect of superimposed TV on ET characteristics. This study reported an effect of NMES frequency on ET magnitude, whereas TV superimposition did not affect this parameter. In the context of our experimental design decisions, the present findings question the clinical use of wide-pulse NMES and its combination with superimposed TV. Yet, further research is needed in order to maximize force production through the occurrence and magnitude of ET.

Assessment of Changes in Laryngeal Configuration and Voice Parameters Among Different Frequencies of Neuromuscular Electrical Stimulation (NMES) and Cumulative Effects of NMES in a Normophonic Subject: A Pilot Study

Neuromuscular electrical stimulation (NMES) is a complementary resource to voice therapy that can be used for the treatment of hypofunctional voice disorders. Although positive clinical studies have been reported, neutral and even potentially harmful effects of NMES are also described in the literature. Furthermore, in the studies examined by the authors, the use of different methods of NMES have been identified, which further contributes to the inconsistent results found among studies. Moreover, limited rationale is provided for the chosen NMES parameters such as electrode placement, frequency of NMES and length of treatment. The aims of this pilot study were to investigate the a) impact of different frequencies of NMES on glottal configuration and vocal fold vibration patterns and b) changes in laryngeal configuration and vocal output across 12 minutes of NMES. Three experiments were carried out looking at changes in laryngeal configuration and voice output using different imaging techniques (fibreoptic nasolaryngoscopy and high-speed video), acoustical analysis (F0, formant analysis, SPL, CPPS and LHSR values), electroglottography (EGG) and Relative Fundamental Frequency (RFF) analyses. Glottal parameters and acoustical measures were recorded before, during, and after stimulation. Data was collected at rest and during phonation. Overall the results showed global changes in laryngeal configuration from normal to hyperfunctional (ie, increased RFF, SPL, CQ, and stiffness). Changes were more pronounced for lower frequencies of NMES and were significant within less than three minutes of application. NMES is an effective resource for the activation of intrinsic laryngeal muscles producing significant levels of adduction within few minutes of application. Lower NMES frequencies produced greater muscle activation when compared to higher frequencies.

Effectiveness of Dry Needling with Percutaneous Electrical Nerve Stimulation of High Frequency Versus Low Frequency in Patients with Myofascial Neck Pain

Percutaneous nerve electrical stimulation is a novel treatment modality for the management of acute and chronic myofascial pain syndrome. To compare the effectiveness of dry needling combined with percutaneous electrical nerve stimulation of low frequency versus high frequency, in patients with chronic myofascial neck pain. Randomized, single-blind trial. Laboratory in an academic institution. A total of 40 volunteer patients with chronic neck pain were randomly divided into 2 groups. All patients initially received deep dry needling in a myofascial trigger point of the upper trapezius. Then, one group received high frequency percutaneous electrical nerve stimulation while the other group received low frequency percutaneous electrical nerve stimulation. The primary outcomes were the visual analog scale and the pressure pain threshold, while Neck Disability Index and Kinesiophobia were secondary outcomes. We detected significant improvements in the visual analog scale score in both groups without differences between them. We did not observe significantly different statistics in either group during the evaluation of data on pressure pain threshold. Limitations of the study include (1) heterogeneity of the sample in relation to gender, with more women, (2) the small sample size (40 patients), (3) the absence of placebo group, and (4) the fact that the treatment is focused exclusively on the upper trapezium myofascial trigger point. . Low and high frequency percutaneous electrical nerve stimulation combined with deep dry needling showed similar effects, since no differences between groups were observed on any of the outcome measures. High and low frequency of percutaneous electrical nerve stimulation generates changes on pain intensity and disability, but not on pressure pain threshold or fear of movement.

Low-Frequency Electrical Stimulation Promotes Satellite Cell Activities to Facilitate Muscle Regeneration at an Early Phase in a Rat Model of Muscle Strain.

The capability of regeneration for skeletal muscle after injury depends on the differentiation and proliferation ability of the resident stem cells called satellite cells. It has been reported that electrical stimulation was widely used in clinical conditions to facilitate muscle regeneration after injury, but the characterization of satellite cell responses to the context of low-frequency electrical stimulation in early-phase muscle strain conditions has not been fully clarified. In this study, we aim to investigate the effects of low-frequency electrical stimulation (frequency: 20 Hz; duration: 30 minutes, twice daily) on satellite cell activities in a rat model for the early phase of muscle strain. Firstly, we adopted our previously developed rat model to mimic the early phase of muscle strain in human. After then, we examined the effects of low-frequency electrical stimulation on histopathological changes of the muscle fiber by hematoxylin and eosin (H&E) staining. Finally, we investigated the effects of low-frequency electrical stimulation on satellite cell proliferation and differentiation by quantification of the expression level of the specific proteins using western blot analyses. The muscle strain in biceps femoris muscles of rats can be induced by high-speed rotation from knee flexion 50° to full knee extension at 960°·s−1 angular velocity during its tetany by activating the sciatic nerve, as evidenced by a widening of the interstitial space between fibers, and more edema or necrosis fibers were detected in the model rats without treatment than in control rats. After treatment with low-frequency electrical stimulation (frequency: 20 Hz; duration: 30 minutes, twice daily), the acute strained biceps femoris muscles of rats showed obvious improvement of histomorphology as indicated by more mature muscle fibers with well-ordered formation with clear boundaries. Consistently, the expression levels of the MyoD and myogenin were marked higher than those in the rats in the animal model group, indicating increased satellite cell proliferating and differentiating activities by low-frequency electrical stimulation. This study shows that low-frequency electrical stimulation provides an effective stimulus to upregulate the protein expression of MyoD/myogenin and accelerate the restoration of structure during the early phase of muscle strain. This may have significance for clinical practice. Optimization of low-frequency electrical stimulation parameters may enhance the therapeutic outcome in patients.

Psychoacoustic tests for perceptual assessment of processor fitting in patients with cochlear implants

Was to study the possibility of using a battery of psychoacoustic tests to assess the tuning of the cochlear implant processor (CI) in deaf patients. The study involved 60 prellingually deaf patients aged 10 to 23 years with oral speech skills. To assess the quality of the CI processor tuning, in addition to traditional methods, a special battery of psychoacoustic tests was used. The first block of tests assessed the perception of the basic characteristics of sound signals (duration, temporal structure, spectrum, timbre) and was used to assess the initial setting. The second block of tests, intended for patients with experience using CI, included tasks to distinguish acoustically similar and dynamically changing signals, etc. At the end of the initial CI setup session, patients with short signal perception problems were identified. Adjusting the frequency of electrical stimulation in patients has increased their ability to distinguish between sounds. During the second tuning session of the CI processor, 6 months later, a group of patients with difficulties in perceiving acoustic information in the low-frequency range was identified - distinguishing melodic intervals, changing the pitch of sounds, highlighting the voice of the target speaker. The «problem» patients underwent additional correction of the CI processor setting and the corresponding auditory training, which improved the test performance and subjective perception of sounds. The use of psychoacoustic tests expands the possibilities of fine tuning the CI processor, taking into account the individual characteristics of the patient's auditory perception at different stages of CI use, especially in «problem» patients.

Adynamic Graciloplasty for Faecal Incontinence in an Adult after Anal Atresia Correction in Infancy – a Case Report

Background. Here we present a case of female patient suffering from bowel incontinence. Case report. The patient underwent unstimulated graciloplasty. Postoperative period was uneventful. After 4 weeks, a course of low frequency electric external stimulation in the area around the neurovascular bundle in the thigh was performed. Patient was evaluated 3 months postoperatively. On inspection, her anus was closed at rest. She stated moderate improvement in her continence and quality of life, her Wexner score was 10 and FISI score was 32 (prior surgery 19 and 44 accordingly). Conclusion. Adynamic graciloplasty seems to be a reasonable method of choice for faecal incontinence.

Higher frequency electrical stimulation enhanced myloglossus satellite cell differentiation by upregulating expression of Pax7 mRNA, MyoD, myogenin and MyHC protein.

We investigated the effect of electrical stimulation (ES) of varying pulse frequency on differentiation and proliferation of canine myloglossus satellite cells in vitro. Cellular viability and proliferation were assayed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) assay and flow cytometry fluorescence-activated cell sorting analysis. Cellular differentiation and expression of mark molecule were assayed by Real Time-PCR and Western blot. With increasing frequency ES, we found a significant increase in Myod (r=0.988, p<0.0001), myogenin (r=0.988, p<0.0001), MyHC-slow (r=0.988, p<0.0001), MyHC-fast (r=0.875, p<0.0001) protein expression, and Pax7 mRNA expression (r=0.712, p=0.001). Pax7 mRNA expression and MyoD, myogenin, and MyHC protein expression were increased with increment of electrical stimulation frequency in myloglossus muscle satellite. Higher frequency ES enhanced myloglossus satellite cell differentiation, not proliferation and viability.

Analgesic Tolerance Development during Repetitive Electric Stimulations Is Associated with Changes in the Expression of Activated Microglia in Rats with Osteoarthritis.

Electric stimulation is used for managing osteoarthritic (OA) pain; however, little is known about the development of analgesic tolerance during repeated stimulations and the relation of spinal microglia with OA pain. We investigated the changes in the analgesic effects of repeated electric stimulations and the relation between the development of analgesic tolerance and spinal microglial expression in rats with OA. To induce OA, monosodium iodoacetate was injected into the synovial space of the right knee joint of the rats (n = 185). Repeated high frequency, low frequency, or sham transcutaneous electric nerve stimulation (TENS) was performed to the ipsilateral knee joint for 20 min in rats with OA (n = 45). Minocycline or minocycline plus TENS (HF, LF, or sham) was treated in OA rats with repeated TENS-induced tolerance (n = 135). Immunohistochemistry of the microglia in the L3–L5 spinal segments was performed. Knee joint pain during passive movement of the knee joint were quantified using the knee-bend score and the proportion of activated microglia was calculated as primary variables. Paw withdrawal threshold (hypersensitivity to mechanical stimuli) was assessed and the resting and activated microglia were counted as secondary variables. Repeated applications decreased the analgesic effect of TENS on OA pain and failed to reduce the expression of activated microglia in the spinal cord. However, spinal microglial inhibition by minocycline restored the analgesic effect of TENS on OA pain in TENS-tolerant OA rats. TENS combined with minocycline treatment improved knee joint pain and mechanical hypersensitivity in TENS-tolerant OA rats, and inhibited the expression of activated microglia in the spinal cord. These results suggest a possible relationship between repetitive electric stimulation-induced analgesic tolerance for OA pain control and changes in microglia activation.

Electroacupuncture protects septic rats from acute lung injury through the JAK1/STAT3 pathway

To explore the protective effect of electroacupuncture against acute lung injury (ALI) in septic rats and explore the mechanism. Sixty male SD rats were randomly divided into cecal ligation and puncture (CLP)-induced sepsis group (n=45) and sham operation group (n=15; with laparotomy but without CLP). The rat models of sepsis were randomized into ALI group (n=15) without further treatment, ALI + SEA group (n=15) treated with electroacupuncture at the point far from the Zusanli acupoint for 30 min, and ALI + EA group (n=15) with electroacupuncture at Zusanli with identical frequency, intensity and duration of electrical stimulation. All the rats were sacrificed at 12 h after CLP for measurement of the weight and the wet/dry weight (W/D) ratio of the lungs. Pathological changes of the lung tissues were examined using HE staining, and the contents of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in the homogenate of the lung tissues were detected using enzyme-linked immunosorbent assay (ELISA). TUNEL staining was used to detect the apoptotic cells, and the expressions of Bax, caspase-3 and the important proteins in the JAK1/STAT3 signaling pathway (JAK1 and STAT3) were detected with Western blotting. Compared with those in the sham operation group, the rats in ALI group showed obvious lung pathologies with significantly increased lung W/D ratio (P < 0.01), pulmonary expressions of TNF-α and IL-6 (P < 0.01), and obvious up-regulation of JAK1, STAT3, caspase-3, and Bax expressions (P < 0.01); similar changes were also observed in ALI+SEA group (P > 0.05). Compared with those in ALI+SEA group, the rats in ALI+EA group showed significantly milder lung pathologies, lowered lung W/D ratio (P < 0.01) and decreased pulmonary expressions of TNF-α, IL-6, JAK1, STAT3, caspase-3 and Bax (P < 0.01). Electroacupuncture can inhibit the release of inflammatory mediators and cell apoptosis via the JAK1/STAT3 pathway to reduce lung injuries in septic rats.

Establishment of a heart-on-a-chip microdevice based on human iPS cells for the evaluation of human heart tissue function

Human iPS cell (iPSC)-derived cardiomyocytes (CMs) hold promise for drug discovery for heart diseases and cardiac toxicity tests. To utilize human iPSC-derived CMs, the establishment of three-dimensional (3D) heart tissues from iPSC-derived CMs and other heart cells, and a sensitive bioassay system to depict physiological heart function are anticipated. We have developed a heart-on-a-chip microdevice (HMD) as a novel system consisting of dynamic culture-based 3D cardiac microtissues derived from human iPSCs and microelectromechanical system (MEMS)-based microfluidic chips. The HMDs could visualize the kinetics of cardiac microtissue pulsations by monitoring particle displacement, which enabled us to quantify the physiological parameters, including fluidic output, pressure, and force. The HMDs demonstrated a strong correlation between particle displacement and the frequency of external electrical stimulation. The transition patterns were validated by a previously reported versatile video-based system to evaluate contractile function. The patterns are also consistent with oscillations of intracellular calcium ion concentration of CMs, which is a fundamental biological component of CM contraction. The HMDs showed a pharmacological response to isoproterenol, a β-adrenoceptor agonist, that resulted in a strong correlation between beating rate and particle displacement. Thus, we have validated the basic performance of HMDs as a resource for human iPSC-based pharmacological investigations.

Electrical stimulation for seizure induction during SEEG exploration: a useful predictor of postoperative seizure recurrence?

ObjectiveDirect electrical stimulations of cerebral cortex are a traditional part of stereoelectroencephalography (SEEG) practice, but their value as a predictive factor for seizure outcome has never been carefully investigated.Patients and...

Transcutaneous tibial nerve stimulation for the treatment of bladder storage symptoms in people with multiple sclerosis: Protocol of a single-arm feasibility study

Background: Neurogenic lower urinary tract dysfunction (NLUTD) is common among people with multiple sclerosis (MS) with a pooled prevalence of 68.41% using self-report measures and 63.95% using urodynamic studies. Transcutaneous tibial nerve stimulation (TTNS) is a non-invasive option to manage bladder storage symptoms; however, the potential efficacy of TTNS among people with MS is based on a small number of studies with the absence of high-quality evidence relating to efficacy, and lack of clarity of the optimal electrical stimulation parameters and frequency, duration and number of treatment sessions. This study aims to assess whether TTNS is feasible and acceptable as a treatment for bladder storage symptoms in people with MS. Methods: We will use a single-arm experimental study to explore the feasibility and acceptability of TTNS in the treatment of bladder storage symptoms in MS. The CONSORT extension for pilot and feasibility studies will be followed to standardise the conduct and reporting of the study. The recruitment plan is twofold: 1) Open recruitment for people with MS through MS Ireland’s communication channels; 2) recruitment from a convenience sample of people with MS who have previously participated in a qualitative interview study of urinary symptoms. We will assess recruitment/retention rates, the urinary symptoms changes and the effect on quality of life pre and post intervention using ICIQ-OAB, 3-day bladder diary, King’s Health Questionnaire and collect self-reported data on adherence and adverse events. Acceptability of using TTNS will be evaluated at the end of intervention. This study has been reviewed and approved by the Education and Health Science’s Faculty Research Ethics Committee, University of Limerick [2020_06_07_EHS]. Conclusion: It is anticipated that assessing the feasibility and acceptability of TTNS for storage bladder symptoms in MS will inform the development of a definitive randomised trial. Trial registration: ClinicalTrials.gov NCT04528784 27/08/2020

Transcutaneous tibial nerve stimulation for the treatment of bladder storage symptoms in people with multiple sclerosis: Protocol of a single-arm feasibility study.

Background: Neurogenic lower urinary tract dysfunction (NLUTD) is common among people with multiple sclerosis (MS) with a pooled prevalence of 68.41% using self-report measures and 63.95% using urodynamic studies. Transcutaneous tibial nerve stimulation (TTNS) is a non-invasive option to manage bladder storage symptoms; however, the potential efficacy of TTNS among people with MS is based on a small number of studies with the absence of high-quality evidence relating to efficacy, and lack of clarity of the optimal electrical stimulation parameters and frequency, duration and number of treatment sessions. This study aims to assess whether TTNS is feasible and acceptable as a treatment for bladder storage symptoms in people with MS. Methods: We will use a single-arm experimental study to explore the feasibility and acceptability of TTNS in the treatment of bladder storage symptoms in MS. The CONSORT extension for pilot and feasibility studies will be followed to standardise the conduct and reporting of the study. The recruitment plan is twofold: 1) Open recruitment for people with MS through MS Ireland's communication channels; 2) recruitment from a convenience sample of people with MS who have previously participated in a qualitative interview study of urinary symptoms. We will assess recruitment/retention rates, the urinary symptoms changes and the effect on quality of life pre and post intervention using ICIQ-OAB, 3-day bladder diary, King's Health Questionnaire and collect self-reported data on adherence and adverse events. Acceptability of using TTNS will be evaluated at the end of intervention. This study has been reviewed and approved by the Education and Health Science's Faculty Research Ethics Committee, University of Limerick [2020_06_07_EHS]. Conclusion: It is anticipated that assessing the feasibility and acceptability of TTNS for storage bladder symptoms in MS will inform the development of a definitive randomised trial. Trial registration: ClinicalTrials.gov NCT04528784 27/08/2020.

O2-030 Anatomo-functional features of BTLA: Study of high frequency electrical cortical stimulation

O2-030 Anatomo-functional features of BTLA: Study of high frequency electrical cortical stimulation

Novel microwire-based biosensor probe for simultaneous real-time measurement of glutamate and GABA dynamics in vitro and in vivo

Glutamate (GLU) and γ-aminobutyric acid (GABA) are the major excitatory (E) and inhibitory (I) neurotransmitters in the brain, respectively. Dysregulation of the E/I ratio is associated with numerous neurological disorders. Enzyme-based microelectrode array biosensors present the potential for improved biocompatibility, localized sample volumes, and much faster sampling rates over existing measurement methods. However, enzymes degrade over time. To overcome the time limitation of permanently implanted microbiosensors, we created a microwire-based biosensor that can be periodically inserted into a permanently implanted cannula. Biosensor coatings were based on our previously developed GLU and reagent-free GABA shank-type biosensor. In addition, the microwire biosensors were in the same geometric plane for the improved acquisition of signals in planar tissue including rodent brain slices, cultured cells, and brain regions with laminar structure. We measured real-time dynamics of GLU and GABA in rat hippocampal slices and observed a significant, nonlinear shift in the E/I ratio from excitatory to inhibitory dominance as electrical stimulation frequency increased from 10 to 140 Hz, suggesting that GABA release is a component of a homeostatic mechanism in the hippocampus to prevent excitotoxic damage. Additionally, we recorded from a freely moving rat over fourteen weeks, inserting fresh biosensors each time, thus demonstrating that the microwire biosensor overcomes the time limitation of permanently implanted biosensors and that the biosensors detect relevant changes in GLU and GABA levels that are consistent with various behaviors.

Influence of Pulse Waveform and Frequency on Evoked Torque, Stimulation Efficiency, and Discomfort in Healthy Subjects.

The aim of the study was to determine the influence of neuromuscular electrical stimulation pulse waveform and frequency on evoked torque, stimulation efficiency, and discomfort at two neuromuscular electrical stimulation levels. This is a repeated measures study. The quadriceps muscle of 24 healthy men was stimulated at submaximal (neuromuscular electrical stimulationsub) and maximal (neuromuscular electrical stimulationmax) levels using two pulse waveforms (symmetrical, asymmetrical) and three pulse frequencies (60, 80, 100 Hz). Repeated measures analysis of variance and effect sizes were used to verify the effect of pulse waveform and pulse frequency on stimulation efficiency (evoked torque/current intensity) and discomfort and to assess the magnitude of the differences, respectively. Stimulation efficiency was higher for symmetrical (neuromuscular electrical stimulationsub = 0.88 ± 0.21 Nm/mA; neuromuscular electrical stimulationmax = 1.27 ± 0.46 Nm/mA) compared with asymmetrical (neuromuscular electrical stimulationsub = 0.77 ± 0.21 Nm/mA; neuromuscular electrical stimulationmax = 1.02 ± 0.34 Nm/mA; P ≤ 0.001; effect size = 0.56-0.66) but did not significantly differ between frequencies (P = 0.17). At both neuromuscular electrical stimulation levels, there were no statistically significant differences in discomfort between pulse waveforms or frequencies. The higher stimulation efficiency of symmetrical pulses suggests that this waveform would be preferred to asymmetrical pulses in clinical practice. Stimulation frequencies between 60 and 100 Hz can be used interchangeably because of similar efficiency and discomfort.

Frequency- and State-Dependent Network Effects of Electrical Stimulation Targeting the Ventral Tegmental Area in Macaques.

The ventral tegmental area (VTA) is a midbrain structure at the heart of the dopaminergic system underlying adaptive behavior. Endogenous firing rates of dopamine cells in the VTA vary from fast phasic bursts to slow tonic activity. Artificial perturbations of the VTA, through electrical or optogenetic stimulation methods, generate different and sometimes even contrasting behavioral outcomes depending on stimulation parameters such as frequency, amplitude, and pulse width. Here, we investigate the global functional effects of electrical stimulation frequency (10, 20, 50, and 100 Hz) of the VTA in rhesus monkeys. We stimulated 2 animals with chronic electrodes, either awake or anesthetized, while concurrently acquiring whole-brain functional magnetic resonance imaging (fMRI) signals. In the awake state, activity as a function of stimulation frequency followed an inverted U-shape in many cortical and subcortical structures, with highest activity observed at 20 and 50 Hz and lower activity at 10 and 100 Hz. Under anesthesia, the hemodynamic responses in connected brain areas were slightly positive at 10 Hz stimulation, but decreased linearly as a function of higher stimulation frequencies. A speculative explanation for the remarkable frequency dependence of stimulation-induced fMRI activity is that the VTA makes use of different frequency channels to communicate with different postsynaptic sites.

Current Perception Threshold Testing in Pharyngeal Paresthesia Patients with Depression or Anxiety.

PurposeSatisfactory quantitative diagnostic approaches to pharyngeal paresthesia patients with depression or anxiety remain to be explored. This study investigated the plausibility of current perception threshold (CPT) testing in diagnosing pharyngeal paresthesia in patients with depression or anxiety.Patients and MethodsA total of 41 patients with pharyngeal paresthesia with depression or anxiety were recruited as the study group. Additionally, 60 healthy volunteers constituted the control group. The CPT values associated with 5-, 250-, and 2000-Hz electrical stimulation frequencies were measured at the palatal lingual arch and posterior third of the lingual body (two sensory nerve distribution sites in the pharynx). The normal range of CPT values of the above three frequencies was analyzed. The differences in the CPT values for sensory nerves were compared.ResultsThere were no significant differences in age and sex between the study and control groups. The CPT values of the pharynx at the two tested sites were not significantly correlated with age and gender. The CPT value of the study group was significantly lower than that of the control group in the palatal lingual arch and posterior third of the lingual body at an electrical stimulation of 5 Hz (p<0.05). No significant differences in the CPT values at other frequencies were found between the two groups.ConclusionCPT testing is effective in determining pharyngeal paresthesia in patients with depression and anxiety. Paresthesia of the pharyngeal sensory nerve region is caused by damaged C fibers.