Optimal Stimulation Frequency Research Articles

Utilising activity patterns of a complex biophysical network model to optimise intra-striatal deep brain stimulation

A large-scale biophysical network model for the isolated striatal body is developed to optimise potential intrastriatal deep brain stimulation applied to, e.g. obsessive-compulsive disorder. The model is based on modified Hodgkin–Huxley equations with small-world connectivity, while the spatial information about the positions of the neurons is taken from a detailed human atlas. The model produces neuronal spatiotemporal activity patterns segregating healthy from pathological conditions. Three biomarkers were used for the optimisation of stimulation protocols regarding stimulation frequency, amplitude and localisation: the mean activity of the entire network, the frequency spectrum of the entire network (rhythmicity) and a combination of the above two. By minimising the deviation of the aforementioned biomarkers from the normal state, we compute the optimal deep brain stimulation parameters, regarding position, amplitude and frequency. Our results suggest that in the DBS optimisation process, there is a clear trade-off between frequency synchronisation and overall network activity, which has also been observed during in vivo studies.

Impact of optimized transcutaneous auricular vagus nerve stimulation on cardiac autonomic profile in healthy subjects and heart failure patients

Objective. To determine the optimal frequency and site of stimulation for transcutaneous vagus nerve stimulation (tVNS) to induce acute changes in the autonomic profile (heart rate (HR), heart rate variability (HRV)) in healthy subjects (HS) and patients with heart failure (HF). Approach. We designed three single-blind, randomized, cross-over studies: (1) to compare the acute effect of left tVNS at 25 Hz and 10 Hz (n = 29, age 60 ± 7 years), (2) to compare the acute effect of left and right tVNS at the best frequency identified in study 1 (n = 28 age 61 ± 7 years), and (3) to compare the acute effect of the identified optimal stimulation protocol with sham stimulation in HS and HF patients (n = 30, age 59 ± 5 years, and n = 32, age 63 ± 7 years, respectively). Main results. In study 1, left tragus stimulation at 25 Hz was more effective than stimulation at 10 Hz in decreasing HR (−1.0 ± 1.2 bpm, p < 0.001 and −0.5 ± 1.6 bpm, respectively) and inducing vagal effects (significant increase in RMSSD, and HF power). In study 2, the HR reduction was greater with left than right tragus stimulation (−0.9 ± 1.5 bpm, p < 0.01 and −0.3 ± 1.4 bpm, respectively). In study 3 in HS, left tVNS at 25 Hz significantly reduced HR, whereas sham stimulation did not (−1.1 ± 1.2 bpm, p< 0.01 and −0.2 ± 2.9 bpm, respectively). In HF patients, both active and sham stimulation produced negligible effects. Significance. Left tVNS at 25 Hz is effective in acute modulation of cardiovascular autonomic control (HR, HRV) in HS but not in HF patients (NCT05789147).

The protective effects of repetitive transcranial magnetic stimulation with different high frequencies on motor functions in MPTP/probenecid induced Parkinsonism mouse models.

High-frequency repeated transcranial magnetic stimulation (rTMS) stimulating the primary motor cortex (M1) is an alternative, adjunctive therapy for improving the motor symptoms of Parkinson's disease (PD). However, whether the high frequency of rTMS positively correlates to the improvement of motor symptoms of PD is still undecided. By controlling for other parameters, a disease animal model may be useful to compare the neuroprotective effects of different high frequencies of rTMS. The current exploratory study was designed to compare the protective effects of four common high frequencies of rTMS (5, 10, 15, and 20Hz) and iTBS (a special form of high-frequency rTMS) and explore the optimal high-frequency rTMS on an animal PD model. Following high frequencies of rTMS application (twice a week for 5weeks) in a MPTP/probenecid-induced chronic PD model, the effects of the five protocols on motor behavior as well as dopaminergic neuron degeneration levels were identified. The underlying molecular mechanisms were further explored. We found that all the high frequencies of rTMS had protective effects on the motor functions of PD models to varying degrees. Among them, the 10, 15, and 20Hz rTMS interventions induced comparable preservation of motor function through the protection of nigrostriatal dopamine neurons. The enhancement of brain-derived neurotrophic factor (BDNF), dopamine transporter (DAT), and vesicular monoamine transporter 2 (VMAT-2)and the suppression of TNF-α and IL-1β in the nigrostriatum were involved in the process. The efficacy of iTBS was inferior to that of the above three protocols. The effect of 5Hz rTMS protocol was weakest. Combined with the results of the present study and the possible side effects induced by rTMS, we concluded that 10Hz might be the optimal stimulation frequency for preserving the motor functions of PD models using rTMS treatment.

Inhibition of tibialis anterior spinal reflex circuits using frequency-specific neuromuscular electrical stimulation.

Neuromuscular electrical stimulation (NMES) can generate muscle contractions and elicit excitability of neural circuits. However, the optimal stimulation frequency for effective neuromodulation remains unclear. Eleven able-bodied individuals participated in our study to examine the effects of: (1) low-frequency NMES at 25 Hz, (2) high-frequency NMES at 100 Hz; and (3) mixed-frequency NMES at 25 and 100 Hz switched every second. NMES was delivered to the right tibialis anterior (TA) muscle for 1 min in each condition. The order of interventions was pseudorandomized between participants with a washout of at least 15 min between conditions. Spinal reflexes were elicited using single-pulse transcutaneous spinal cord stimulation applied over the lumbar enlargement to evoke responses in multiple lower-limb muscles bilaterally and maximum motor responses (Mmax) were elicited in the TA muscle by stimulating the common peroneal nerve to assess fatigue at the baseline and immediately, 5, 10, and 15 min after each intervention. Our results showed that spinal reflexes were significantly inhibited immediately after the mixed-frequency NMES, and for at least 15 min in follow-up. Low-frequency NMES inhibited spinal reflexes 5 min after the intervention, and also persisted for at least 10 min. These effects were present only in the stimulated TA muscle, while other contralateral and ipsilateral muscles were unaffected. Mmax responses were not affected by any intervention. Our results indicate that even a short-duration (1 min) NMES intervention using low- and mixed-frequency NMES could inhibit spinal reflex excitability of the TA muscle without inducing fatigue.

Effects of acupoints-based TENS combined with tDCS on spasticity and motor function in ischemic stroke with spastic hemiplegia: study protocol for a randomized controlled trial

BackgroundSpastic hemiplegia following ischemic strokes seriously impedes the recovery of motor function posing a vast rehabilitation challenge. As the uncertain effects of recommended conventional treatments such as botulinum toxin injections on active functional improvement and potential adverse effects cannot be bypassed, there is an increasing need in alternative, more effective and safer modalities. Acupoints-based transcutaneous electrical nerve stimulation (Acu-TENS) and transcranial direct current stimulation (tDCS) are effective non-invasive modalities for stroke rehabilitation, particularly showing anti-spastic effect and functional improvements as well. However, the optimal stimulation frequency of Acu-TENS and whether combination of Acu-TENS and tDCS exert synergistic effect remain to be investigated.ObjectiveTo evaluate the effects of Acu-TENS combined with tDCS on spasticity and motor function in ischemic stroke patients with spastic hemiplegia and screen the optimal frequency of Acu-TENS.MethodsA total of 90 post-ischemic stroke patients with spastic hemiplegia will be intervened for 4 weeks and followed up for 4 weeks. They will be randomly assigned to three groups including two observation groups and a standard care control group in a 1:1:1 ratio. All patients will receive standard care and regular rehabilitation accordingly. In addition, the two observation groups will receive 12 sessions of Acu-TENS at 20 Hz or 100 Hz for 30 min combined with 1 mA tDCS for 20 min, three times a week, for 4 weeks. The primary outcome is the change in total modified Ashworth scale (MAS) score from baseline to week 4. Secondary outcomes include changes in surface electromyography (SEMG), Fugl-Meyer Motor Function Scale, Modified Barthel Index (MBI), and 10-meter walk test from baseline to week 4. MAS score will also be measured after 4 weeks of follow-up. Adverse events throughout the study will be recorded.DiscussionThis trial will evaluate, for the first time, the therapeutic potentials and safety of Acu-TENS combined with tDCS on spasticity and motor function in stroke patients. It will provide evidence for frequency-dependent anti-spastic effect of Acu-TENS, and a reference for rated parameter setting of new mixed transcutaneous and transcranial stimulation system for stroke rehabilitation, thereby promoting proactive healthcare consequently.Trial registration:Chinese Clinical Trials Register ChiCTR2200067186.

Changes in Optimal Stimulation Frequency With Time for Gait Disturbances in Patients With PD After STN DBS - A Longitudinal Study

Changes in Optimal Stimulation Frequency With Time for Gait Disturbances in Patients With PD After STN DBS - A Longitudinal Study

Optimizing the modulation paradigm of transcutaneous auricular vagus nerve stimulation in patients with disorders of consciousness: A prospective exploratory pilot study protocol.

Transcutaneous auricular vagus nerve stimulation (taVNS) is a non-invasive neuromodulation technique. Several studies have reported the effectiveness of taVNS in patients with disorders of consciousness (DOC); however, differences in the modulation paradigm have led to inconsistent treatment outcomes. This prospective exploratory trial will include 15 patients with a minimally conscious state (MCS) recruited according to the coma recovery scale-revised (CRS-R). Each patient will receive 5 different frequencies of taVNS (1, 10, 25, 50, and 100 Hz); sham stimulation will be used as a blank control. The order of stimulation will be randomized, and the patients' CRS-R scores and resting electroencephalography (EEG) before and after stimulation will be recorded. The overall study of taVNS used in treating patients with DOC is still in the preliminary stage of exploration. Through this experiment, we aim to explore the optimal stimulation frequency parameters of taVNS for the treatment of DOC patients. Furthermore, we expect to achieve a stable improvement of consciousness in DOC patients by continuously optimizing the neuromodulation paradigm of taVNS for the treatment of DOC patients. https://www.chictr.org.cn/index.aspx, identifier ChiCTR 2200063828.

Effect of Acupoint Therapies on Postoperative Sleep Quality: A Narrative Review.

Several studies have reported that sleep quality often decreases in patients after surgery, especially in elderly patients, which seriously affects postoperative prognosis and outcomes, inducing diseases such as postoperative delirium, long-term chronic pain, and potentially fatal cardiovascular events. With the popularization of comfortable medicine, medical workers pay more attention to the postoperative sleep quality of patients. The causes underlying the decrease in postoperative sleep quality may include postoperative pain, the severity of surgical trauma and stress, perioperative anxiety and depression, and postoperative complications. Patients with insomnia often use acupoint therapies as a safe and effective alternative to drugs. Acupoint therapies are among the oldest medical therapies of Traditional Chinese Medicine and are gradually gaining recognition among medical workers worldwide. Various types of acupoint stimulation methods such as transcutaneous electrical acupoint simulation (TEAS), acupressure, acupuncture, and electroacupuncture can change the brain's local electrical activity, inhibit the central nervous system, and achieve deep sedation through stimulating the related acupoints, which provides a novel idea and basis for improvement in factors affecting postoperative sleep quality. This review explores the mechanism of acupoint therapies from several aspects of affecting the sleep quality of patients after surgery and its clinical results. We found that acupoint therapies effectively improve sleep quality and alleviate the postoperative complications of patients, and we emphasize the importance of acupoint therapies to guide future research and clinical practice. Large-scale, multicenter studies are needed to determine the optimal duration, frequency, and timing of acupoint stimulation for improving postoperative sleep quality.

Changes in Optimal Stimulation Frequency with Time for Gait Disturbances in Patients with PD after STN-DBS—A Longitudinal Study

Abstract Aim: To assess the changes in frequency parameters of STN-DBS stimulation over 6 months required to optimize gait in PD patients. Methods: It’s a single center, open label longitudinal study of PD patients after STN-DBS with gait disorders. Gait assessment using stand–walk–sit (SWS) test and freezing of gait (FOG) scores were done at baseline and after 6 months. Gait was assessed in five frequencies settings, that is, 60 Hz, 90 Hz, 130 Hz, 180 Hz and stimulation “OFF” during medication ON state. Voltage was maintained. Results: Fifteen post-deep brain stimulation (DBS) patients were included. Mean duration after surgery was 3.73 ± 2.82 years. In SWS and FOG at baseline, five patients have good response at 180 Hz frequency, five at 130 Hz, one at 90 Hz, two patients at 60 Hz, one both 60 and 90 Hz, and one at both 90 and 180 HZ. And after 6 months out of the 13 patients who were able to perform the test, four patients had good response at 180 Hz frequency, four at 130 Hz, two at 90 Hz, one each for 60 Hz and battery OFF state, and one for both 130 Hz and 180 Hz. At 6 months, four patients had good response at the same frequency as baseline, while 11 patients have change in frequency from baseline. Conclusion: Optimal frequency for gait varies in patients—both low and high frequency may be useful. Optimal frequency for improving gait changes over period of time. Regular assessment and changing frequency may improve gait after DBS.

The visual cortical responses to sinusoidal transcorneal electrical stimulation

Retinal stimulation has become a widely utilized approach to restore visual function for individuals with retinal degenerative diseases. Although the rectangular electrical pulse is the primary stimulus waveform used in retinal neuromodulation, it remains unclear whether alternate waveforms may be more effective. Here, we used the optical intrinsic signal imaging system to assess the responses of cats’ visual cortex to sinusoidal electrical stimulation through contact lens electrode, analyzing the response to various stimulus parameters (frequency, intensity, pulse width). A comparison between sinusoidal and rectangular stimulus waveform was also investigated. The results indicated that the optimal stimulation frequency for sinusoidal electrical stimulation was approximately 20 Hz, supporting the hypothesis that low-frequency electrostimulation induces more responsiveness in retinal neurons than high-frequency electrostimulation in case of sinusoidal stimulation. We also demonstrated that for low-frequency retinal neuromodulation, sinusoidal pulses are more effective than rectangular ones. In addition, we found that compared to current intensity, the effect of the sinusoidal pulse width on cortical responses was more prominent. These results suggested that sinusoidal electrical stimulation may provide a promising strategy for improved retinal neuromodulation in clinical settings.

Strength-frequency curve for micromagnetic neurostimulation through excitatory postsynaptic potentials (EPSPs) on rat hippocampal neurons and numerical modeling of magnetic microcoil (μcoil)

Objective. The objective of this study was to measure the effect of micromagnetic stimulation (μMS) on hippocampal neurons, by using single microcoil (μcoil) prototype, magnetic pen (MagPen). MagPen will be used to stimulate the CA3 region magnetically and excitatory post synaptic potential (EPSP) response measurements will be made from the CA1 region. The threshold for micromagnetic neurostimulation as a function of stimulation frequency of the current driving the µcoil will be demonstrated. Finally, the optimal stimulation frequency of the current driving the μcoil to minimize power will be estimated. Approach. A biocompatible, watertight, non-corrosive prototype, MagPen was built, and customized such that it is easy to adjust the orientation of the μcoil and its distance over the hippocampal tissue in an in vitro recording setting. Finite element modeling of the μcoil design was performed to estimate the spatial profiles of the magnetic flux density (in T) and the induced electric fields (in V m−1). The induced electric field profiles generated at different values of current applied to the µcoil can elicit a neuronal response, which was validated by numerical modeling. The modeling settings for the μcoil were replicated in experiments on rat hippocampal neurons. Main results. The preferred orientation of MagPen over the Schaffer Collateral fibers was demonstrated such that they elicit a neuron response. The recorded EPSPs from CA1 region due to μMS at CA3 region were validated by applying tetrodotoxin (TTX). Application of TTX to the hippocampal slice blocked the EPSPs from μMS while after prolonged TTX washout, a partial recovery of the EPSP from μMS was observed. Finally, it was interpreted through numerical analysis that increasing frequency of the current driving the μcoil, led to a decrease in the current amplitude threshold for micromagnetic neurostimulation. Significance. This work reports that micromagnetic neurostimulation can be used to evoke population EPSP responses in the CA1 region of the hippocampus. It demonstrates the strength-frequency curve for µMS and its unique features related to orientation dependence of the µcoils, spatial selectivity and stimulation threshold related to distance dependence. Finally, the challenges related to µMS experiments were studied including ways to overcome them.

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.

Investigating a Lock-In Thermal Imaging Setup for the Detection and Characterization of Magnetic Nanoparticles.

Magnetic hyperthermia treatments utilize the heat generated by magnetic nanoparticles stimulated by an alternating magnetic field. Therefore, analytical methods are required to precisely characterize the dissipated thermal energy and to evaluate potential amplifying or diminishing factors in order to ensure optimal treatment conditions. Here, we present a lock-in thermal imaging setup specifically designed to thermally measure magnetic nanoparticles and we investigate theoretically how the various experimental parameters may influence the measurement. We compare two detection methods and highlight how an affordable microbolometer can achieve identical sensitivity with respect to a thermal camera-based system by adapting the measurement time. Furthermore, a numerical model is used to demonstrate the optimal stimulation frequency, the degree of nanomaterial heating power, preferential sample holder dimensions and the extent of heat losses to the environment. Using this model, we also revisit some technical assumptions and experimental results that previous studies have stated and suggest an optimal experimental configuration.

SPARC: Method for Overcoming Temporal Dispersion in Unmyelinated Nerves for Imaging C Fibres with Electrical Impedance Tomography (EIT)

Fast neural EIT is a novel technique that enables imaging of evoked myelinated fibre activity in fascicles in rat sciatic nerve in vivo. However, imaging unmyelinated fibres is challenging due to temporal dispersion of the neural activity, caused by variability in fibre conduction velocities. This reduces the signal to below noise several centimetres from onset. The purpose of this work was to develop a method to overcome dispersion and allow EIT recordings of phasic activity at any distance from onset along the nerve.MethodsCompound impedance changes (dZ) were simulated using an electrically stimulated CAPs in 1D FEM model of a C fibre [1], with statistical analysis for 5000 fibres with conduction velocities 0.6±0.07 m/s (mean±SD) [2]. This enabled simulation of dZ up to 20 cm from the stimulus with stimulus trains of 5/10/20/50 Hz lasting 0.25–8 s with 3 s intervals between trains (Fig. 1a). The total duration of each simulation was 100 s.dZ was simulated 1) By coherent averaging of responses of supramaximal activity of single spikes [3] with demodulation bandwidth of 50–300 Hz and 2) By bandpass filtering of entire evoked spike trains with bandwidths of 0.25–5 Hz which allowed significant reduction of the noise without the need for coherent spike averaging.Random gaussian noise (0.015 μV RMS) was added to the signal to simulate realistic recording conditions. The SNR in the utilised approaches was computed for all tested stimulation and recording paradigms and compared.ResultsWhile coherent spike averaging was superior at short distances, its SNR fell exponentially with the distance from the onset (Fig. 1b, solid lines). The SNR with the compound demodulation was more consistent across distances (~2 at the optimal stimulation frequency of 20 Hz, Fig. 1b, dashed lines) allowing recording at ≥ 20 cm from stimulation. The estimated minimal averaging time required to obtain an SNR of 4 at 20 cm from the stimulus was equal to approximately 30 minutes at 20 Hz.Conclusion and future workThe developed stimulation and signal processing paradigm demonstrated the feasibility of dZ recording at long distances from the stimulus. Future work is to validate it on the ex vivo crustacean leg nerve model and subsequently an in vivo mammalian model with the final objective of imaging C fibres in the vagus nerve in humans. If successful, this technique will be applied for improvement of the emerging field of bioelectronic medicines [4].Support or Funding InformationThe work was supported by NIH SPARC grant no: 3OT2OD026545‐01S2.(a) Example of AP and dZ responses of the C fibre subjected to repetitive 50 Hz stimuli; (b) SNR computed for the single and compound recording paradigms.Figure 1

Brain Stimulation to Modulate Food Intake and Eating Behavior.

Appetitive behaviors are mediated through homeostatic and reward signaling of brain circuits. There has been increasing interest in the use of neuromodulation techniques aimed at targeting brain regions such as the lateral prefrontal and subcortical regions associated with dysregulation of eating behaviors. Invasive brain stimulation techniques have demonstrated promising results in treating severe and enduring anorexia nervosa and morbid obesity. In addition, non-invasive techniques have been shown to successfully reduce food craving, hunger ratings, and calorie intake as well as binge/purge symptoms in eating disorders. Brain stimulation offers promising results for treating symptoms associated with eating disorders and modifying appetitive behaviors including craving and caloric consumption. Future research should focus on identifying optimal frequency and duration of stimulation and employ longitudinal studies to assess long-term effectiveness on clinical outcomes such as eating disorder symptomatology, weight loss, and sustained improvements in eating behaviors over time.

Optimal stimulation frequency for vibrational optical coherence elastography.

Vibrational optical coherence elastography (OCE) is a promising tool for extracting the mechanical property of soft tissue. Purpose of this study is focusing on settling the optimal frequency range for vibrational OCE with evenly distributed stress filed. A finite element model of 2% agar phantom was built by ANSYS with a vibration stimulation frequency range from 200 to 3000 Hz. Practical experiments were carried out for cross-validation with the same frequencies and sample. Lateral and horizontal stress filed distributions under different frequencies were mathematically evaluated by coefficient of variance and degree of linearity. Results from simulation and practical experiment cross-validated each other and 1000 Hz was set as the maximum ideal frequency for vibrational OCE, while the minimum frequency is set by theoretical calculation with a result of 250 Hz. An ex vivo biological sample was utilised to testify performance of vibrational OCE with excitation frequencies in and out of concluded optimal range, which showed that stiffness was better mapped out in optimal frequency range.

Toward Electrophysiology-Based Intelligent Adaptive Deep Brain Stimulation for Movement Disorders.

Deep brain stimulation (DBS) represents one of the major clinical breakthroughs in the age of translational neuroscience. In 1987, Benabid and colleagues demonstrated that high-frequency stimulation can mimic the effects of ablative neurosurgery in Parkinson's disease (PD), while offering two key advantages to previous procedures: adjustability and reversibility. Deep brain stimulation is now an established therapeutic approach that robustly alleviates symptoms in patients with movement disorders, such as Parkinson's disease, essential tremor, and dystonia, who present with inadequate or adverse responses to medication. Currently, stimulation electrodes are implanted in specific target regions of the basal ganglia-thalamic circuit and stimulation pulses are delivered chronically. To achieve optimal therapeutic effect, stimulation frequency, amplitude, and pulse width must be adjusted on a patient-specific basis by a movement disorders specialist. The finding that pathological neural activity can be sampled directly from the target region using the DBS electrode has inspired a novel DBS paradigm: closed-loop adaptive DBS (aDBS). The goal of this strategy is to identify pathological and physiologically normal patterns of neuronal activity that can be used to adapt stimulation parameters to the concurrent therapeutic demand. This review will give detailed insight into potential biomarkers and discuss next-generation strategies, implementing advances in artificial intelligence, to further elevate the therapeutic potential of DBS by capitalizing on its modifiable nature. Development of intelligent aDBS, with an ability to deliver highly personalized treatment regimens and to create symptom-specific therapeutic strategies in real-time, could allow for significant further improvements in the quality of life for movement disorders patients with DBS that ultimately could outperform traditional drug treatment.

Extraction and Analysis of Steady State Somatosensory Evoked Potentials in Lower Limbs

Steady state somatosensory evoked potential (SSSEP) is an electrical signal generated in the cerebral cortex under external auxiliary stimulation. In the current literature, there are few studies on the extraction method of SSSEP in lower limbs. In order to be able to extract an effective SSSEP from lower limbs, electrical stimulation with different intensity is executed on the posterior tibial nerve of inner ankle of lower limbs. Select the optimal stimulation frequency combination among 5 stimulation frequency combinations through time-frequency analysis and brain topographic map. The results show that the electrical stimulation intensity of lower limbs is generally about 8 mA~25 mA, and the stimulation intensity of the left and right leg is different. The optimal stimulation frequency combination of the lower limbs is 28 Hz-33 Hz, with the best spectral characteristics for the subject at this frequency combination.

T06. Outcome of brain responsive neurostimulation in refractory epilepsy cases from a single tertiary epilepsy centre

Introduction Responsive Neurostimulation (RNS) provides an alternative treatment for medication-refractory epilepsy cases which are not a candidate for resective epilepsy surgery. It has been shown effective with complication rates comparable to similar procedures. This study reports the data on responsive neurostimulation patients from Massachusetts General Hospital (MGH) for the first time. Methods We retrospectively studied all patients who were implanted with RNS at MGH, which was from October 2006 to July 2017. We collected data on age of implantation, sex, and the localization of epileptogenic zone. The seizure reduction was calculated by subtracting the frequency of seizures per month in the last visit after implantation (report of past 6 months) from the seizure frequency before implantation. This was divided by seizure frequency before RNS implantation and reported in percentage. For calculating the responder rate, we excluded the three cases that received stimulation less than 6 months. Also we reviewed the rate of different complications associated with RNS. Results 25 patients (12 female and 13 male) ranging from 20 to 65 years old (mean ± std: 37.4 ± 12.6) were implanted with RNS from October 2006 to July 2017. One patient was explanted after 2 months due to wound infection so it was excluded from seizure outcome analyses. In terms of epileptogenic zone, 11 cases were neocortical, 9 cases were bilateral mesiotemporal, 2 cases were left mesiotemporal, 2 cases were left mesiotemporal and neocortical and 1 case was thalamic. The seizure reduction percentage ranged between 0% and 100% with median reduction of 88%. The responder rate (patients with >50% seizure reduction) was 76.19% (16 out of 21 patients) and the super-responder rate (patients with >90% seizure reduction) was 57.14% (12 out of 21 patients). There was a positive correlation between seizure reduction and time from implantation which means patients who had the RNS for longer showed better outcome (Spearman correlation: r = 0.43, p = 0.067).There was no significant difference in average seizure reduction percentage between neocortical (mean: 45.75 %) and bilateral mesiotemporal (mean: 70.00%) cases (p: 0.351). Seventeen patients had no post-operative complication (68%), 4 patients had intracranial hemorrhage (16%), 2 patients had wound infection (8%), 1 patient had headache (4%) and 1 patient had wound dehiscence (4%). Conclusion This study shows that RNS has been an effective treatment modality in medication refractory epilepsy cases at MGH, with minimal complications. The improvement of outcome over time supports the hypothesis that RNS may function through seizure network modulation. Future works are needed to find optimal frequency and length of stimulation to achieve faster and more efficacious network modulation.