Slow Wave Frequency Research Articles

Быстрые и медленные электромагнитные волны в продольно намагниченном тонкопленочном ферромагнитном метаматериале

The results of a theoretical study of the electrodynamic characteristics of fast and slow electromagnetic waves (EMWs) propagating in a metamaterial are presented. The metamaterial consists of a ferromagnetic film inside which a periodic lattice of thin metal wires is located. It has been established that the ferromagnetic thin-film metamaterial possesses the properties of a left-handed medium at frequencies of slow electromagnetic waves. It is shown that, in a ferromagnetic metamaterial, compared with a conventional ferromagnetic film, the cutoff frequencies of fast and slow EMWs shift to a higher frequency range, and EMWs themselves become strongly slowed waves.

High-Density Multichannel Electrode Array Improves the Accuracy of Cutaneous Electrogastrography Across Subjects With Wide-Ranging BMI

Introduction: The cutaneous electrogastrogram (EGG) is a noninvasive technique for measuring gastric myoelectric activity. The size, position and shape of the stomach vary considerably depending on body mass index, fed/fasting state and age (Lamart et al, 2013). In this study, we assessed how the placement of EGG electrodes can influence the ability to detect normal gastric slow waves. Methods: Eleven asymptomatic subjects (8M/3F, age 21—77 years) with an average BMI of 26 (range 21.8—36.3) were enrolled. Subjects were excluded if they had any active foregut symptoms on the PAGI—SYM questionnaire. We placed 100 EGG electrodes in a uniform 10x10 grid (2cm x 2cm spacing) on the abdominal wall extending inferiorly from the sternum at the top with reference and ground electrodes on the subject's right side. The locations of the umbilicus and xiphoid relative to the array were documented as anatomical references. After 30 minutes of fasting recording, each subject consumed a standardized meal and the study was continued for 90 minutes. The signal—to—noise ratio (SNR) for each electrode pair was calculated, defined as the average power between 0.04 Hz and 0.06 Hz divided by the average power in all other frequencies between 0.02 Hz and 0.20 Hz. We calculated the percentage of normal gastric slow waves, i.e., 2—4 cpm activity. The results from the highest SNR electrode pair were compared to those from the traditional single—channel EGG placement: one electrode halfway between the xiphoid and umbilicus and the second electrode placed 4—6 cm to the subject's left. Results: Using the highest SNR electrode pair, the percentage of normal slow waves was 92 ± 8%, and all 11 subjects were over the 70% threshold that defines normal. When using the traditional EGG electrode placement, however, this value dropped significantly to 68 ± 16%, and 6/11 subjects fell below 70% (see Table 1; Figure 1). Statistical significance of p = 4.4 x 10—5 was determined by a two—sided t—test for the null hypothesis that the two related samples have identical average values. This effect was particularly pronounced for the high BMI subjects.1235_A Figure 1. Improved detection of gastric slow wave frequency with a high—density EGG array versus traditional lead placement.Conclusion: Standardization of cutaneous lead placement for EGG may be confounded by anatomical variability in stomach location coupled with an increased sensitivity to lead placement due to low signal amplitude. The results from this study suggest that multiple electrodes or a priori stomach localization can improve accurate detection of the gastric slow wave.1235_B Figure 2. Determination of normal gastric slow wave based on traditional EGG location versus highest EGG SNR location with a high density array.

Height variation of the cutoff frequency in a sunspot umbra

Context. In the solar atmosphere, the acoustic cutoff frequency is a local quantity that depends on atmospheric height. It separates low-frequency evanescent waves from high-frequency propagating waves. Aims. We measure the cutoff frequency of slow magnetoacoustic waves at various heights of a sunspot umbra and compare the results with the estimations from several analytical formulae. Methods. We analyzed the oscillations in the umbra of a sunspot belonging to active region NOAA 12662 observed in the 10 830 Å spectral region with the GREGOR Infrared Spectrograph and in the Fe I 5435 Å line with the GREGOR Fabry-Pérot Interferometer. Both instruments are attached to the GREGOR telescope at the Observatorio del Teide, Tenerife, Spain. We computed the phase and amplification spectra between the velocity measured from various pairs of lines that sample various heights of the solar atmosphere. The cutoff frequency and its height variation were estimated from the inspection of the spectra. Results. At the deep umbral photosphere the cutoff frequency is around 5 mHz and it increases to 6 mHz at higher photospheric layers. At the chromosphere the cutoff is ~3.1 mHz. A comparison of the observationally determined cutoff with the theoretically predicted values reveals an agreement in the general trend and a reasonable match at the chromosphere, but also significant quantitative differences at the photosphere. Conclusions. Our analyses show strong evidence of the variation of the cutoff frequency with height in a sunspot umbra, which is not fully accounted for by current analytical estimations. This result has implications for our understanding of wave propagation, the seismology of active regions, and the evaluation of heating mechanisms based on compressible waves.

Electrical stimulation with motility analysis of five parts of the gastrointestinal tract

Abstract Gastrointestinal (GI) motility disorders are frequent and clinically significant conditions with impairment of patient’s quality of life. Examples range from upper GI symptoms such as dysphagia and gastroparesis to lower GI manifestations, namely chronic-intestinal pseudo obstruction, diarrhea and constipation. Furthermore, postoperative motility disorders are common. Currently, available pharmacological or dietetic treatment options are limited. Since GI motility is based on myoelectric activity, electrical stimulation (ES) is a promising alternative. Numerous studies have demonstrated suitable pacing strategies and parameters in different GI segments. However, results of multilocular ES are rare. We report the first experimental study to evaluate ES of five GI parts in a porcine model. Multi-channel electromyography (EMG) recordings of gastrointestinal baseline and poststimulatory electrical activity were realized together with video-based marker tracking (VBMT). ES provoked visible GI contractions and appeared to modulate frequencies of slow waves and spikes. Further investigations are needed for analysis of locoregional and cross-organ effects of ES on the GI tract.

Slow wave contraction frequency plateaux in the small intestine are composed of discrete waves of interval increase associated with dislocations.

What is the central question of this study? What is the nature of slow wave-driven contraction frequency gradients in the small intestine? What is the main finding and its importance? Frequency plateaux are composed of discrete waves of increased interval, each wave associated with a contraction dislocation. Smooth frequency gradients are generated by localized neural modulation of wave frequency, leading to functionally important wave turbulence. Both patterns are emergent properties of a network of coupled oscillators, the interstitial cells of Cajal. A gut-wide network of interstitial cells of Cajal generates electrical oscillations (slow waves) that orchestrate waves of muscle contraction. In the small intestine there is a gradient in slow wave frequency from high at the duodenum to low at the terminal ileum. Time-averaged measurements of frequency have suggested either a smooth or a stepped (plateaued) gradient. We measured individual contraction intervals from diameter maps of the mouse small intestine to create interval maps (IMaps). The IMaps showed that each frequency plateau was composed of discrete waves of increased interval. Each interval wave originated at a terminating contraction wave, a 'dislocation', at the proximal boundary of the plateau. In a model chain of coupled phase oscillators, interval wave frequency increased as coupling decreased or as the natural frequency gradient or noise increased. Injuring the intestine at a proximal point, to destroy coupling, suppressed distal steps, which then reappeared with gap junction block by carbenoxolone. This lent further support to our previous hypothesis that lines of dislocations were fixed by points of low coupling strength. Dislocations, induced by electrical field pulses in the intestine and by equivalent phase shift in the model, were associated with interval waves. When the enteric nervous system was active, IMaps showed a chaotic, turbulent pattern of interval change, with no frequency steps or plateaux. This probably resulted from local, stochastic release of neurotransmitters. Plateaux, dislocations, interval waves and wave turbulence arise from a dynamic interplay between natural frequency and coupling in the network of interstitial cells of Cajal.

Establishment of a radiotelemetric recording technique in mice to investigate gastric slow waves: Modulatory role of putative neurotransmitter systems

What is the central question of this study? Gastric slow waves originating from the interstitial cells of Cajal-smooth muscle syncytium are usually studied in culture or in tissue segments, but nobody has described recordings of slow waves from awake, freely moving mice. Can radiotelemetry be used to record slow waves, and do they respond predictably to drug treatment? What is the main finding and its importance? Radiotelemetry can be used to record slow waves from awake, freely moving mice, permitting an examination of drug actions in vivo, which is crucial to drug discovery projects for characterizing the effects of drugs and metabolites on gastrointestinal function. The mouse is the most commonly used species in preclinical research, and isolated tissues are used to study slow waves from the interstitial cells of Cajal-smooth muscle syncytium of the gastrointestinal tract. The aim of this study was to establish a radiotelemetric technique in awake mice to record gastric myoelectric activity from the antrum to gain insight into the effects of endogenous modulatory systems on slow waves. Under general anaesthesia, two biopotential wires from a telemetry transmitter were sutured into the antrum of male ICR (imprinting control region) mice. The animals were allowed 1week to recover from surgery before the i.p. administration of drugs to stimulate or inhibit slow waves. The basal dominant frequency of slow waves was 6.96±0.43c.p.m., and the percentages of power in the bradygastric, normogastric and tachygastric ranges were 6.89±0.98, 37.32±1.72 and 34.38±0.77%, respectively (n=74). Nicotine at 1mgkg-1 increased normogastric power, but at 3mgkg-1 it increased bradygastric power (P<0.05). Metoclopramide at 10mgkg-1 increased normogastric power; sodium nitroprusside at 10mgkg-1 had latent effects on tachygastric power (P<0.05); and l-NAME at 10mgkg-1 had no effect (P>0.05). Nicotine and bethanechol also caused varying degrees of hypothermia (>1°C reductions; P<0.05). In conclusion, radiotelemetry can be used to record slow waves from awake, freely moving mice. In light of our findings, we recommend that studies assessing slow waves should also assess body temperature simultaneously.

A Combined Methodology to Eliminate Artifacts in Multichannel Electrogastrogram Based on Independent Component Analysis and Ensemble Empirical Mode Decomposition

Cutaneous measurements of electrogastrogram (EGG) signals are heavily contaminated by artifacts due to cardiac activity, breathing, motion artifacts, and electrode drifts whose effective elimination remains an open problem. A common methodology is proposed by combining independent component analysis (ICA) and ensemble empirical mode decomposition (EEMD) to denoise gastric slow-wave signals in multichannel EGG data. Sixteen electrodes are fixed over the upper abdomen to measure the EGG signals under three gastric conditions, namely, preprandial, postprandial immediately, and postprandial 2 h after food for three healthy subjects and a subject with a gastric disorder. Instantaneous frequencies of intrinsic mode functions that are obtained by applying the EEMD technique are analyzed to individually identify and remove each of the artifacts. A critical investigation on the proposed ICA-EEMD method reveals its ability to provide a higher attenuation of artifacts and lower distortion than those obtained by the ICA-EMD method and conventional techniques, like bandpass and adaptive filtering. Characteristic changes in the slow-wave frequencies across the three gastric conditions could be determined from the denoised signals for all the cases. The results therefore encourage the use of the EEMD-based technique for denoising gastric signals to be used in clinical practice.

Application of the Gabor Transform for Analysis of Electromyographic Signals of the Intestine in the Low-Frequency Region

The Gabor transform allows quantitative estimation of the non-stationarity of the electromyographic signal in the low-frequency region with the maxim permissible time–frequency resolution. The calculation of the parameters of the Gabor transform was conducted on different time and frequency intervals to estimate the slow-wave activity of the intestine. It was demonstrated that the efficient size of the 32-s time window, which provides the efficient resolution of the frequency spectrum at 0.01 Hz, is suitable for the accurate study of the change in the frequency of slow waves. The ability to construct the dependence of the change in the frequency of slow waves of electromyograms on time with the specified accuracy was demonstrated.

Extracellular Cl- regulates electrical slow waves and setting of smooth muscle membrane potential by interstitial cells of Cajal in mouse jejunum.

What is the central question of this study? The aim was to investigate the roles of extracellular chloride in electrical slow waves and resting membrane potential of mouse jejunal smooth muscle by replacing chloride with the impermeant anions gluconate and isethionate. What is the main finding and its importance? The main finding was that in smooth muscle cells, the resting Cl- conductance is low, whereas transmembrane Cl- movement in interstitial cells of Cajal (ICCs) is a major contributor to the shape of electrical slow waves. Furthermore, the data confirm that ICCs set the smooth muscle membrane potential and that altering Cl- homeostasis in ICCs can alter the smooth muscle membrane potential. Intracellular Cl- homeostasis is regulated by anion-permeable channels and transporters and contributes to excitability of many cell types, including smooth muscle and interstitial cells of Cajal (ICCs). Our aims were to investigate the effects on electrical activity in mouse jejunal muscle strips of replacing extracellular Cl- (Cl-o ) with the impermeant anions gluconate and isethionate. On reducing Cl-o , effects were observed on electrical slow waves, with small effects on smooth muscle membrane voltage (Em ). Restoration of Cl- hyperpolarized smooth muscle Em proportional to the change in Cl-o concentration. Replacement of 90% of Cl-o with gluconate reversibly abolished slow waves in five of nine preparations. Slow waves were maintained in isethionate. Gluconate and isethionate substitution had similar concentration-dependent effects on peak amplitude, frequency, width at half peak amplitude, rise time and decay time of residual slow waves. Gluconate reduced free ionized Ca2+ in Krebs solutions to 0.13mm. In Krebs solutions containing normal Cl- and 0.13mm free Ca2+ , slow wave frequency was lower, width at half peak amplitude was smaller, and decay time was faster. The transient hyperpolarization following restoration of Cl-o was not observed in W/Wv mice, which lack pacemaker ICCs in the small intestine. We conclude that in smooth muscle cells, the resting Cl- conductance is low, whereas transmembrane Cl- movement in ICCs plays a major role in generation or propagation of slow waves. Furthermore, these data support a role for ICCs in setting smooth muscle Em and that altering Cl- homeostasis in ICCs can alter smooth muscle Em .

Preliminary study on high resolution mapping in human gastric electrical activities

Objective To investigate the spatio-temporal characteristics of normal gastric electrical activity. Methods From January 1st to February 29th, 2016, fasting gastric electric slow wave signal was collected by high resolution mapping (HRM) under anesthesia before operation in patients without gastric lesions but needed laparoscopic surgery. Parameters of slow wave signal activity was calculated, gastric activity map and velocities was drawn and then spatio-temporal characteristics of gastric electrical activity of different part of the stomach were obtained. Independent sample t test was performed for comparison of two groups and one-way analysis of variance was used for multiple group comparisons. Results The normal gastric pacing zone located in the upper middle part of gastric body near greater curvature. Electrical activity of gastric body spread to gastric antrum along the long axis of the stomach. No slow signal was recorded in the gastric fundus and the gastric cardia. The frequencies of slow waves of different parts of gastric was same and the mean value was 2.61±0.11 cycle per minute. Compared with that of gastric body, the slow wave amplitude of gastric pacing zone was higher ((4.19±0.73) mV vs (1.67±0.89) mV) and the speed was faster (7.24±1.37) mm/s vs (4.94±0.20) mm/s); the differences were statistically significant (t=18.89 and 4.95, both P 0.05). Conclusions The normal human gastric pacemaker is located in mid and upper corpus near the greater curvature, which produces slow wave and control whole gastric electrical activity. The amplitude and velocity of slow waves are in gradient changes in different gastric regions. HRM is a mature and reliable research method to study the spatio-temporal characteristics of gastric electrical activity, which provides the possibility for the study of abnormal gastric electrical activity. Key words: Slow wave; ICC; Gastric electrical activity; Submucosal tumor; High-resolution mapping

Relationships between gastric slow wave frequency, velocity, and extracellular amplitude studied by a joint experimental-theoretical approach.

Gastric slow wave dysrhythmias are accompanied by deviations in frequency, velocity, and extracellular amplitude, but the inherent association between these parameters in normal activity still requires clarification. This study quantified these associations using a joint experimental-theoretical approach. Gastric pacing was conducted in pigs with simultaneous high-resolution slow wave mapping (32-256 electrodes; 4-7.6mm spacing). Relationships between period, velocity, and amplitude were quantified and correlated for each wavefront. Human data from two existing mapping control cohorts were analyzed to extract and correlate these same parameters. A validated biophysically based ICC model was also applied in silico to quantify velocity-period relationships during entrainment simulations and velocity-amplitude relationships from membrane potential equations. Porcine pacing studies identified positive correlations for velocity-period (0.13mms-1 per 1s, r2 =.63, P<.001) and amplitude-velocity (74μV per 1mms-1 , r2 =.21, P=.002). In humans, positive correlations were also quantified for velocity-period (corpus: 0.11mms-1 per 1s, r2 =.16, P<.001; antrum: 0.23mms-1 per 1s, r2 =.55; P<.001), and amplitude-velocity (94μV per 1mms-1 , r2 =.56; P<.001). Entrainment simulations matched the experimental velocity-period relationships and demonstrated dependence on the slow wave recovery phase. Simulated membrane potential relationships were close to these experimental results (100μV per 1mms-1 ). These data quantify the relationships between slow wave frequency, velocity, and extracellular amplitude. The results from both human and porcine studies were in keeping with biophysical models, demonstrating concordance with ICC biophysics. These relationships are important in the regulation of gastric motility and will help to guide interpretations of dysrhythmias.

Ambulatory gastric mucosal slow wave recording for chronic experimental studies.

Dysrhythmic bioelectric slow wave activity have been implicated in major functional motility disorders such as gastroparesis and chronic unexplained nausea and vomiting, but its correlation to symptoms is still unclear. For patients with severe gastroparesis, high-frequency gastric stimulation is offered as a therapy in some centers. Temporary gastric electrical stimulation has also been proposed an approach to screen patients who would benefit from the implantation of a permanent stimulator. In this study we introduced novel methods for recording slow wave activity from the gastric mucosa during the entire temporary stimulation phase of 5 days, in 3 patients. An ambulatory recording system was applied to record 3 channels of mucosal slow wave activity, as well as three axis accelerometer data to monitor when the patient was mobile. Techniques were developed to detect large movements and these time periods were excluded from analyses of mucosal slow waves. The frequency and amplitude of the slow waves was calculated in a 5 min segment, with 75% overlap, for the entire duration. In feasibility studies, the slow wave frequency and amplitude for the patients were 3.0±0.96 cpm and 1.43±1.75 mV. Large variations in slow wave amplitude were seen in comparsion to slow wave frequency, which were concordant with previous studies. The use of the ambulatory system will allow for investigation of pathophysiology, correlation of electrophysiology data to patient symptoms and to determine the effects of post-prandial and noctural slow wave patterns. We anticipate that future use of slow wave information alongside patient symptoms may allow improved selection of patients for stimulaton techniques.

Identifying the effects of microsaccades in tripolar EEG signals.

Microsaccades are tiny, involuntary eye movements that occur during fixation, and they are necessary to human sight to maintain a sharp image and correct the effects of other fixational movements. Researchers have theorized and studied the effects of microsaccades on electroencephalography (EEG) signals to understand and eliminate the unwanted artifacts from EEG. The tripolar concentric ring electrode (TCRE) sensors are used to acquire TCRE EEG (tEEG). The tEEG detects extremely focal signals from directly below the TCRE sensor. We have noticed a slow wave frequency found in some tEEG recordings. Therefore, we conducted the current work to determine if there was a correlation between the slow wave in the tEEG and the microsaccades. This was done by analyzing the coherence of the frequency spectrums of both tEEG and eye movement in recordings where microsaccades are present. Our preliminary findings show that there is a correlation between the two.

Brain Activation by H1 Antihistamines Challenges Conventional View of Their Mechanism of Action in Motion Sickness: A Behavioral, c-Fos and Physiological Study in Suncus murinus (House Musk Shrew).

Motion sickness occurs under a variety of circumstances and is common in the general population. It is usually associated with changes in gastric motility, and hypothermia, which are argued to be surrogate markers for nausea; there are also reports that respiratory function is affected. As laboratory rodents are incapable of vomiting, Suncus murinus was used to model motion sickness and to investigate changes in gastric myoelectric activity (GMA) and temperature homeostasis using radiotelemetry, whilst also simultaneously investigating changes in respiratory function using whole body plethysmography. The anti-emetic potential of the highly selective histamine H1 receptor antagonists, mepyramine (brain penetrant), and cetirizine (non-brain penetrant), along with the muscarinic receptor antagonist, scopolamine, were investigated in the present study. On isolated ileal segments from Suncus murinus, both mepyramine and cetirizine non-competitively antagonized the contractile action of histamine with pKb values of 7.5 and 8.4, respectively; scopolamine competitively antagonized the contractile action of acetylcholine with pA2 of 9.5. In responding animals, motion (1 Hz, 4 cm horizontal displacement, 10 min) increased the percentage of the power of bradygastria, and decreased the percentage power of normogastria whilst also causing hypothermia. Animals also exhibited an increase in respiratory rate and a reduction in tidal volume. Mepyramine (50 mg/kg, i.p.) and scopolamine (10 mg/kg, i.p.), but not cetirizine (10 mg/kg, i.p.), significantly antagonized motion-induced emesis but did not reverse the motion-induced disruptions of GMA, or hypothermia, or effects on respiration. Burst analysis of plethysmographic-derived waveforms showed mepyramine also had increased the inter-retch+vomit frequency, and emetic episode duration. Immunohistochemistry demonstrated that motion alone did not induce c-fos expression in the brain. Paradoxically, mepyramine increased c-fos in brain areas regulating emesis control, and caused hypothermia; it also appeared to cause sedation and reduced the dominant frequency of slow waves. In conclusion, motion-induced emesis was associated with a disruption of GMA, respiration, and hypothermia. Mepyramine was a more efficacious anti-emetic than cetirizine, suggesting an important role of centrally-located H1 receptors. The ability of mepyramine to elevate c-fos provides a new perspective on how H1 receptors are involved in mechanisms of emesis control.

1173 FATIGUE AND SLEEP SLOW OSCILLATIONS ARE ASSOCIATED WITH WHITE MATTER INTEGRITY FOLLOWING MODERATE TO SEVERE TRAUMATIC BRAIN INJURY

Chronic sleep-wake disturbances are among the most invalidating and frequently reported symptoms following a traumatic brain injury (TBI), but their pathophysiological mechanisms are still poorly understood. We aimed to explore potential mechanisms by which anatomical damage due to TBI, more specifically white matter damage, can cause the reported symptoms. Twenty-three subjects (17M/6F; age: 31 ± 11 years) were tested 23 ± 9 months following a moderate to severe TBI (Glasgow Coma Scale Score at hospital admission: 8.1 ± 2.9); twenty-seven age- and sex-matched healthy controls were also tested. Magnetic resonance imaging (3T) including a diffusion weighted sequence, 1-night polysomnography, and sleep questionnaires (Pittsburgh Sleep Quality Index, Fatigue Severity Scale and Epworth Sleepiness Scale) were used. Voxelwise t-tests and correlations were carried out with FSL, using tract-based spatial statistics and the Randomise tool. Extensive white matter damage (i.e. increased diffusivity and reduced anisotropy) was observed for most cerebral tracks in TBI subjects compared to controls. TBI subjects also had lower slow wave frequency (F=6.9; p=0.01), longer negative and positive phase durations (F=4.0–8.0; p=0.05-0.007), and reduced slope (F=4.8; p=0.03). In TBI participants, lower white matter integrity was associated with higher slow wave amplitude (r=0.46–0.79; p<0.05), longer positive and negative phase durations (r=0.69, p<0.05; r=0.55–0.67, p<0.05, respectively), as well as with higher subjective fatigue (r=0.06–0.08; p<0.05). These results suggest that TBI subjects with greater damage in white matter track integrity report more fatigue symptoms and have larger and elongated sleep slow waves. These slow waves may represent a mechanism that compensates for a possible higher mental effort exerted to accomplish tasks during the day. Our results bring new elements to explain the pathophysiology of post-TBI fatigue and sleep disturbances. Canadian Institutes of Health Research (CIHR), Fonds de Recherche Santé-Québec (FRSQ)

A theoretical analysis of anatomical and functional intestinal slow wave re-entry

Intestinal bioelectrical slow waves are a key regulator of intestinal motility. Peripheral pacemakers, ectopic initiations and sustained periods of re-entrant activities have all been experimentally observed to be important factors in setting the frequency of intestinal slow waves, but the tissue-level mechanisms underpinning these activities are unclear. This theoretical analysis aimed to define the initiation, maintenance, and termination criteria of two classes of intestinal re-entrant activities: anatomical re-entry and functional re-entry. Anatomical re-entry was modeled in a three-dimensional (3D) cylindrical model, and functional rotor was modeled in a 2D rectangle model. A single-pulse stimulus was used to invoke an anatomical re-entry and a prolonged refractory block was used to invoke the rotor. In both cases, the simulated re-entrant activities operated at frequencies above the baseline entrainment frequency. The anatomical re-entry simulation results demonstrated that a temporary functional refractory block would be required to initiate the re-entrant activity in a single direction around the cylindrical model. The rotor could be terminated by a single-pulse stimulus delivered around the core of the rotor. In conclusion, the simulation results provide the following new insights into the mechanisms of intestinal re-entry: (i) anatomical re-entry is only maintained within a specific range of velocities, outside of which the re-entrant activities become either an ectopic activity or simultaneous activations of the intestinal wall; (ii) a maintained rotor entrained slow waves faster in the antegrade direction than in the retrograde direction. Simulations are shown to be a valuable tool for achieving novel insights into the mechanisms of intestinal slow wave dysrhythmia.

Su1552 - Relationships between Slow Wave Frequency, Conduction Velocity and Amplitude in the Human Stomach

Su1552 - Relationships between Slow Wave Frequency, Conduction Velocity and Amplitude in the Human Stomach

MP63-07 CHARACTERIZATION OF LOW AMPLITUDE RHYTHMIC CONTRACTIONS DURING URODYNAMICS

You have accessJournal of UrologyUrodynamics/Lower Urinary Tract Dysfunction/Female Pelvic Medicine: Incontinence: Evaluation (Urodynamic Testing)1 Apr 2017MP63-07 CHARACTERIZATION OF LOW AMPLITUDE RHYTHMIC CONTRACTIONS DURING URODYNAMICS Zachary Cullingsworth, Brooks Kelly, William Simmons, Andrew Colhoun, Anna Nagle, Randy Vince, John Speich, and Adam Klausner Zachary CullingsworthZachary Cullingsworth More articles by this author , Brooks KellyBrooks Kelly More articles by this author , William SimmonsWilliam Simmons More articles by this author , Andrew ColhounAndrew Colhoun More articles by this author , Anna NagleAnna Nagle More articles by this author , Randy VinceRandy Vince More articles by this author , John SpeichJohn Speich More articles by this author , and Adam KlausnerAdam Klausner More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2017.02.1959AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Human detrusor smooth muscle (DSM) can exhibit low amplitude rhythmic contractions (LARC) which may contribute to overactive bladder (OAB) in some patients. The aim of this study was to develop an objective method to identify LARC during urodynamics (UD), categorize patients with significant LARC, and potentially begin to characterize a LARC-mediated OAB/detrusor overactivity subtype. METHODS An algorithm was developed to analyze UD filling data in low volume (1st 410 seconds) and high volume (final 410s) regions. Fast Fourier Transform (FFT) analysis identified the frequency (F) in the 1-6 cycle/min range associated with the maximum amplitude of the vesical pressure (Pves) in each region (Fig 1). A patient-specific range of interest corresponding to F ± 0.5 cycles/min was determined. Pves and Pabd amplitudes were analyzed separately to identify both significant (higher than average) and independent (distinct from Pabd) Pves signals. To be significant, Pves amplitude must be > 1.35 standard deviations (SD) above average Pves amplitude. To be independent, the Pabd amplitude must be < 1.35 SD above the average Pabd amplitude. SD of 1.35 was chosen using an iterative process in 0.05 SD increments to identify the maximum number of significant and independent signals. RESULTS This algorithm was used to retrospectively analyze 43 consecutive UD studies which included 25 (14 neurogenic, 11 idiopathic) with detrusor overactivity (58%). The average age of the entire group was 55±2 years and included 14 men and 29 women. FFT analysis identified a significant and independent Pves signal in 12/43 patients (28%) of which 8/12 (67%, 5 neurogenic, 3 idiopathic) had detrusor overactivity. The average age of patients with significant and independent signals was 54±5 years and included 6 men and 6 women. CONCLUSIONS Analysis of LARC during UD testing identified a subset of patients with a significant and independent slow wave frequency in Pves. Further refinements of this technique may help identify subsets of individuals with LARC-mediated OAB/detrusor overactivity. © 2017FiguresReferencesRelatedDetails Volume 197Issue 4SApril 2017Page: e838 Advertisement Copyright & Permissions© 2017MetricsAuthor Information Zachary Cullingsworth More articles by this author Brooks Kelly More articles by this author William Simmons More articles by this author Andrew Colhoun More articles by this author Anna Nagle More articles by this author Randy Vince More articles by this author John Speich More articles by this author Adam Klausner More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Acute Slow Wave Responses to High-Frequency Gastric Electrical Stimulation in Patients With Gastroparesis Defined by High-Resolution Mapping

High-frequency gastric electrical stimulation (GES) has emerged as a therapy for gastroparesis, but the mechanism(s) of action remain unclear. There is a need to refine stimulation protocols for clinical benefit, but a lack of accurate techniques for assessing mechanisms in clinical trials, such as slow wave modulation, has hindered progress. We thereby aimed to assess acute slow wave responses to GES in gastroparesis patients using high-resolution (HR) (multi-electrode) mapping, across a range of stimulation doses achievable by the Enterra stimulation device (Medtronic Inc., MN, USA). Patients with medically refractory gastroparesis (n = 8) undergoing device implantation underwent intraoperative HR mapping (256 electrodes). Baseline recordings were followed by four protocols of increasing stimulation intensity, with washout periods. Slow wave patterns, frequency, velocity, amplitude, and dysrhythmia rates were quantified by investigators blinded to stimulation settings. There was no difference in slow wave pattern, frequency, velocity, or amplitude between baseline, washout, and stimulation periods (all p > 0.5). Dysrhythmias included ectopic pacemakers, conduction blocks, retrograde propagation, and colliding wavefronts, and dysrhythmia rates were unchanged with stimulation off vs. on (31% vs. 36% duration dysrhythmic; p > 0.5). Symptom scores and gastric emptying were improved at 5.8 month follow-up (p < 0.05). High-frequency GES protocols achievable from a current commercial device did not acutely modulate slow wave activity or dysrhythmias. This study advances clinical methods for identifying and assessing therapeutic GES parameters, and can be applied in future studies on higher-energy protocols and devices.

Characterization of oscillatory changes in hippocampus and amygdala after deep brain stimulation of the infralimbic prefrontal cortex

Deep brain stimulation (DBS) is a new investigational therapy that has generated positive results in refractory depression. Although the neurochemical and behavioral effects of DBS have been examined, less attention has been paid to the influence of DBS on the network dynamics between different brain areas, which could contribute to its therapeutic effects. Herein, we set out to identify the effects of 1 h DBS in the infralimbic cortex (IL) on the oscillatory network dynamics between hippocampus and basolateral amygdala (BLA), two regions implicated in depression and its treatment. Urethane‐anesthetized rats with bilaterally implanted electrodes in the IL were exposed to 1 h constant stimulation of 130 Hz of frequency, 60 μA of constant current intensity and biphasic pulse width of 80 μsec. After a period of baseline recording, local field potentials (LFP) were recorded with formvar‐insulated stainless steel electrodes. DBS of the IL increased the power of slow wave (SW, <1.5 Hz) and theta (3–12 Hz) frequencies in the hippocampus and BLA. Furthermore, IL DBS caused a precise coupling in different frequency bands between both brain structures. The increases in SW band synchronization in hippocampus and BLA after DBS suggest that these changes may be important for the improvement of depressive behavior. In addition, the augmentation in theta synchrony might contribute to improvement in emotional and cognitive processes.