scholarly journals Intracranial EEG in the 21st Century

2020 ◽  
Vol 20 (4) ◽  
pp. 180-188 ◽  
Author(s):  
Barbara C. Jobst ◽  
Fabrice Bartolomei ◽  
Beate Diehl ◽  
Birgit Frauscher ◽  
Philippe Kahane ◽  
...  
Keyword(s):  
Epilepsy Surgery ◽  
21St Century ◽  
High Frequency ◽  
Low Frequency ◽  
Epileptogenic Zone ◽  
Noninvasive Methods ◽  
Intracranial Eeg ◽  
Advantages And Disadvantages ◽  
Gamma Range ◽  
The Future

Intracranial electroencephalography (iEEG) has been the mainstay of identifying the seizure onset zone (SOZ), a key diagnostic procedure in addition to neuroimaging when considering epilepsy surgery. In many patients, iEEG has been the basis for resective epilepsy surgery, to date still the most successful treatment for drug-resistant epilepsy. Intracranial EEG determines the location and resectability of the SOZ. Advances in recording and implantation of iEEG provide multiple options in the 21st century. This not only includes the choice between subdural electrodes (SDE) and stereoelectroencephalography (SEEG) but also includes the implantation and recordings from microelectrodes. Before iEEG implantation, especially in magnetic resonance imaging -negative epilepsy, a clear hypothesis for seizure generation and propagation should be based on noninvasive methods. Intracranial EEG implantation should be planned by a multidisciplinary team considering epileptic networks. Recordings from SDE and SEEG have both their advantages and disadvantages. Stereo-EEG seems to have a lower rate of complications that are clinically significant, but has limitations in spatial sampling of the cortical surface. Stereo-EEG can sample deeper areas of the brain including deep sulci and hard to reach areas such as the insula.  To determine the epileptogenic zone, interictal and ictal information should be taken into consideration. Interictal spiking, low frequency slowing, as well as high frequency oscillations may inform about the epileptogenic zone. Ictally, high frequency onsets in the beta/gamma range are usually associated with the SOZ, but specialized recordings with combined macro and microelectrodes may in the future educate us about onset in higher frequency bands. Stimulation of intracranial electrodes triggering habitual seizures can assist in identifying the SOZ. Advanced computational methods such as determining the epileptogenicity index and similar measures may enhance standard clinical interpretation. Improved techniques to record and interpret iEEG may in the future lead to a greater proportion of patients being seizure free after epilepsy surgery.

Intelligent Transformer: Possibilities and Challenges

2011 ◽  
Vol 29 (1) ◽  
pp. 95-100 ◽  
Author(s):  
Beldjajev Viktor ◽  
Roasto Indrek ◽  
Lehtla Tõnu
Keyword(s):  
Energy Management ◽  
Low Frequency ◽  
Power Production ◽  
Future Trends ◽  
Advantages And Disadvantages ◽  
Autonomous Networks ◽  
Production And Consumption ◽  
Wide Range ◽  
The Future

Intelligent Transformer: Possibilities and Challenges This paper covers the concept of an intelligent transformer that is a good candidate to replace a conventional low frequency transformer in the microgrids. As the power production and consumption can vary in a wide range, the new substations have to meet many requirements to guarantee reliable energy management in the autonomous networks. Different topologies of intelligent transformers can be used to meet these requirements. Therefore the advantages and disadvantages of the existing topologies were analyzed. The future trends and challenges are also discussed.

scholarly journals Does the high-frequency data is helpful for forecasting Russian inflation?

2021 ◽  
Vol 37 (2) ◽  
pp. 318-343
Author(s):  
Dmitriy Tretyakov ◽  
◽  
Nikita Fokin ◽  
Keyword(s):  
Monetary Policy ◽  
Central Bank ◽  
High Frequency ◽  
Inflation Targeting ◽  
Low Frequency ◽  
High Frequency Data ◽  
Frequency Data ◽  
Policy Regime ◽  
The Future ◽  
Forecasting Inflation

Due to the fact that at the end of 2014 the Central Bank made the transition to a new monetary policy regime for Russia — the inflation targeting regime, the problem of forecasting inflation rates became more relevant than ever. In the new monetary policy regime, it is important for the Bank of Russia to estimate the future inflation rate as quickly as possible in order to take measures to return inflation to the target level. In addition, for effective monetary policy, the households must trust the actions of monetary authorities and they must be aware of the future dynamics of inflation. Thus, to manage inflationary expectations of economic agents, the Central Bank should actively use the information channel, publish accurate forecasts of consumer price growth. The aim of this work is to build a model for nowcasting, as well as short-term forecasting of the rate of Russian inflation using high-frequency data. Using this type of data in models for forecasting is very promising, since this approach allows to use more information about the dynamics of macroeconomic indicators. The paper shows that using MIDAS model with weekly frequency series (RUB/USD exchange rate, the interbank rate MIACR, oil prices) has more accurate forecast of monthly inflation compared to several basic models, which only use low-frequency data.

scholarly journals Single note dissonance through harmonic self-interference

2016 ◽  
Vol 9 (1) ◽  
Author(s):  
Maxwell Ng
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
The Future ◽  
Qualitative Effect

In music, dissonance is the unpleasant quality of sound. While dissonance is generally regarded as arising from two notes played simultaneously, low frequency notes sound dissonant when played alone on a piano. I hypothesize that this dissonance arises from the harmonics of the played note interfering with one another. Using the piano as a model, perceived dissonance was calculated through the combination of the two-tone dissonance formula with the A-weighting curve and the different harmonic intensities of a piano. Spectrographs of sample piano notes were used to compare harmonics of low frequency and high frequency notes.Single note dissonance increased rapidly as note frequency decreased. A-weighting had no qualitative effect on the dissonance-frequency trend, implying a physical and not a psychoacoustic cause. As verified in the spectrographs, the lower register note had harmonics closer together, compared to the higher register note. It is thus possible that the harmonics of low notes interfere significantly with each other, thereby producing the observed single-note dissonance.The simulation produces a score for the perceived dissonance of a single-note played on the piano. This analysis could be adapted in the future to other instruments, including aerophones, as well as integrate timbre, partials, and inharmonics. La dissonance musicale et pour la plupart compris en matière de deux notes simultanées. Cependant, les notes de basse fréquence semble en désordre quand ils sont joués seules sur un piano. L’explication proposée dans cet oeuvre est que cette dissonance se produit des harmoniques des notes qui s’interfèrent. Utilisant le piano comme exemple, la dissonance perçue a été calculé par la combination de la formule de dissonance entre deux notes avec la courbe de pondération A et les intensités harmoniques d’un piano. Les spectres sonores des notes de piano ont été utilisés pour la comparaison des notes de basse et haut fréquences. La dissonance des seules notes augmentait rapidement alors que les fréquences des notes diminuaient. La pondération A n’avait pas eu un effet sur la tendance entre la dissonance et les fréquences, qui signifie la présence d’une cause physique au lieu d’une cause auditive. Vérifié dans les spectres sonores, la note de registre inférieur avait ses harmoniques plus proches comparés à la note du registre plus haut. C’est alors possible que les harmoniques des notes des registres inférieurs interfèrent considérablement avec les unes les autres, et produit ainsi la dissonance des seules notes observée dans les calculs. La simulation produit un résultat pour la dissonance perçue sur un piano. Cette analyse pourrait être adaptée dans le futur aux autres instruments, incluant les aérophones, et puis intégrer aussi des analyses de timbre, des tons simples, et des inharmoniques.

scholarly journals Comparison of Low and High Frequency Partial Discharge Measurements on Stator Windings

2019 ◽  
pp. 134-138
Author(s):  
Greg C Stone ◽  
Howard Sedding
Keyword(s):  
High Frequency ◽  
Partial Discharge ◽  
Low Frequency ◽  
International Standards ◽  
Very High Frequency ◽  
Stator Windings ◽  
Advantages And Disadvantages ◽  
On Line ◽  
Winding Insulation

Partial discharge (PD) testing has been used for over 60 years primarily as a method to assess condition of the stator winding insulation in motors and generators rated 6 kV and above. More recently it has also been used by some machine manufacturers as a means of assuring the quality of the insulation on single winding elements (coils and bars). Although both on-line and off-line tests mainly use a high voltage capacitor to detect the PD, the PD measuring systems in use work either in the low frequency (LF) regime (less than about 1 MHz) or in the very high frequency (VHF) (30-300 MHz) range. By reference to several international standards, published work as well as some experiments described in this contribution, the advantages and disadvantages of the two approaches are compared. Based on this work, it is now clear that off-line PD tests should be done in the LF range. For on-line tests, either method may be used, but use of the VHF method has become more widespread with machine end users, since the owners themselves can perform and interpret the results with a relatively low risk of false indications.

scholarly journals HIGH-FREQUENCY ELECTROCORTICOGRAPHIC MARKER OF EPILEPTOGENIC ZONE

2019 ◽  
Vol 5 (6) ◽  
pp. 23-30 ◽  
Author(s):  
N. B. Arkhipova ◽  
A. Yu. Ulitin ◽  
M. M. Tastanbekov ◽  
M. V. Aleksandrov
Keyword(s):  
Surgical Treatment ◽  
Epilepsy Surgery ◽  
High Frequency ◽  
Activity Index ◽  
High Frequency Component ◽  
Seizure Outcome ◽  
Bioelectrical Activity ◽  
Epileptogenic Zone ◽  
Potential Marker ◽  
Structural Epilepsy

Background. The search for new markers of the epileptogenic zone (EZ) for the surgical treatment of epilepsy is currently of relevance. Pathological high-frequency oscillations (pHFO) are considered to be a potential marker for EZ. Papers devoted to this topic are few and insufficiently systematized, mostly due to a small quantity of patients.Objective. This study was aimed to determine the diagnostic efficacy of high-frequency electrocorticography (HF ECoG) based on the epilepsy surgery outcomes.Design and methods. This is an original retrospective study of high-frequency bioelectrical activity parameters in 114 patients who underwent surgical treatment in the Polenov Neurosurgical Institute Clinic during 2017–2018. In the subgroup of patients with pharmacoresistant course of structural epilepsy (21 patients) on the preresective electrocorticogram, the pHFO index was higher than in the subgroup with intracerebral neoplasms (11 patients), which may be associated with a longer history and severity of the disease.Results. Through the analysis of the high-frequency component of the post-resective HF ECoG, it was shown that the presence or absence of pHFO in the range of 250–500 Hz does not affect the seizure outcome. The dynamics of the high-frequency activity index before and after the resection are statistically significant for the seizure outcome prediction for structural epilepsy surgery. In this study, the specificity of the pHFO dynamics analysis technique was 85.71 % and sensitivity equaled 58.33 %.Conclusion. Thus, the HF ECoG and the assessment of the dynamics of the pHFO index in the range of 250–500 Hz can complement the traditional method of intraoperative ECoG in the range of up to 70 Hz, including the prediction of the results of surgical treatment. 

scholarly journals Intracranial EEG Biomarkers for Seizure Lateralization in Rapidly-Bisynchronous Epilepsy After Laser Corpus Callosotomy

2021 ◽  
Vol 12 ◽  
Author(s):  
Simon Khuvis ◽  
Sean T. Hwang ◽  
Ashesh D. Mehta
Keyword(s):  
High Frequency ◽  
Detection Threshold ◽  
Low Frequency ◽  
Ground Truth ◽  
Line Length ◽  
High Frequency Oscillation ◽  
Corpus Callosotomy ◽  
Intracranial Eeg ◽  
Interictal Epileptiform Discharge ◽  
High Gamma

Objective: It has been asserted that high-frequency analysis of intracranial EEG (iEEG) data may yield information useful in localizing epileptogenic foci.Methods: We tested whether proposed biomarkers could predict lateralization based on iEEG data collected prior to corpus callosotomy (CC) in three patients with bisynchronous epilepsy, whose seizures lateralized definitively post-CC. Lateralization data derived from algorithmically-computed ictal phase-locked high gamma (PLHG), high gamma amplitude (HGA), and low-frequency (filtered) line length (LFLL), as well as interictal high-frequency oscillation (HFO) and interictal epileptiform discharge (IED) rate metrics were compared against ground-truth lateralization from post-CC ictal iEEG.Results: Pre-CC unilateral IEDs were more frequent on the more-pathologic side in all subjects. HFO rate predicted lateralization in one subject, but was sensitive to detection threshold. On pre-CC data, no ictal metric showed better predictive power than any other. All post-corpus callosotomy seizures lateralized to the pathological hemisphere using PLHG, HGA, and LFLL metrics.Conclusions: While quantitative metrics of IED rate and ictal HGA, PHLG, and LFLL all accurately lateralize based on post-CC iEEG, only IED rate consistently did so based on pre-CC data.Significance: Quantitative analysis of IEDs may be useful in lateralizing seizure pathology. More work is needed to develop reliable techniques for high-frequency iEEG analysis.

scholarly journals A spiking neural network (SNN) for detecting high frequency oscillations (HFOs) in the intraoperative ECoG

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Karla Burelo ◽  
Mohammadali Sharifshazileh ◽  
Niklaus Krayenbühl ◽  
Georgia Ramantani ◽  
Giacomo Indiveri ◽  
...  
Keyword(s):  
Neural Network ◽  
Real Time ◽  
Epilepsy Surgery ◽  
High Frequency ◽  
Seizure Outcome ◽  
Seizure Freedom ◽  
Epileptogenic Zone ◽  
Spiking Neural Network ◽  
High Frequency Oscillations ◽  
Neuromorphic Hardware

AbstractTo achieve seizure freedom, epilepsy surgery requires the complete resection of the epileptogenic brain tissue. In intraoperative electrocorticography (ECoG) recordings, high frequency oscillations (HFOs) generated by epileptogenic tissue can be used to tailor the resection margin. However, automatic detection of HFOs in real-time remains an open challenge. Here we present a spiking neural network (SNN) for automatic HFO detection that is optimally suited for neuromorphic hardware implementation. We trained the SNN to detect HFO signals measured from intraoperative ECoG on-line, using an independently labeled dataset (58 min, 16 recordings). We targeted the detection of HFOs in the fast ripple frequency range (250-500 Hz) and compared the network results with the labeled HFO data. We endowed the SNN with a novel artifact rejection mechanism to suppress sharp transients and demonstrate its effectiveness on the ECoG dataset. The HFO rates (median 6.6 HFO/min in pre-resection recordings) detected by this SNN are comparable to those published in the dataset (Spearman’s $$\rho$$ ρ = 0.81). The postsurgical seizure outcome was “predicted” with 100% (CI [63 100%]) accuracy for all 8 patients. These results provide a further step towards the construction of a real-time portable battery-operated HFO detection system that can be used during epilepsy surgery to guide the resection of the epileptogenic zone.

scholarly journals Blinded study: prospectively defined high frequency oscillations predict seizure outcome in individual patients

2021 ◽  
Author(s):  
Vasileios Dimakopoulos ◽  
Pierre Mégevand ◽  
Ece Boran ◽  
Shahan Momjian ◽  
Margitta Seeck ◽  
...  
Keyword(s):  
Epilepsy Surgery ◽  
High Frequency ◽  
Dwell Time ◽  
Seizure Outcome ◽  
Seizure Freedom ◽  
Intracranial Eeg ◽  
Retest Reliability ◽  
High Frequency Oscillations ◽  
Test Retest Reliability

Abstract Interictal high frequency oscillations are discussed as biomarkers for epileptogenic brain tissue that should be resected in epilepsy surgery to achieve seizure freedom. The prospective classification of tissue sampled by individual electrode contacts remains a challenge. We have developed an automated, prospective definition of clinically relevant high frequency oscillations in intracranial EEG from Montreal and tested it in recordings from Zurich. We here validated the algorithm on intracranial EEG that was recorded in an independent epilepsy centre so that the analysis was blinded to seizure outcome. We selected consecutive patients who underwent resective epilepsy surgery in Geneva with postsurgical follow-up > 12 months. We analysed long-term recordings during sleep that we segmented into intervals of 5 minutes. High frequency oscillations were defined in the ripple (80-250 Hz) and the fast ripple (250-500 Hz) frequency bands. Contacts with the highest rate of ripples co-occurring with fast ripples designated the relevant area. As a validity criterion, we calculated the test-retest reliability of the high frequency oscillations area between the 5 min intervals (dwell time ≥50%). If the area was not fully resected and the patient suffered from recurrent seizures, this was classified as a true positive prediction. We included recordings from 16 patients (median age 32 years, range 18-53 years) with stereotactic depth electrodes and/or with subdural electrode grids (median follow-up 27 months, range 12-55 months). For each patient, we included several 5 min intervals (median 17 intervals). The relevant area had high test-retest reliability across intervals (median dwell time 95%). In two patients, the test-retest reliability was too low (dwell time < 50%) so that outcome prediction was not possible. The area was fully included in the resected volume in 2/4 patients who achieved postoperative seizure freedom (specificity 50%) and was not fully included in 9/10 patients with recurrent seizures (sensitivity 90%), leading to an accuracy of 79%. An additional exploratory analysis suggested that high frequency oscillations were associated with interictal epileptic discharges only in channels within the relevant area and not associated in channels outside the area. We thereby validated the automated procedure to delineate the clinically relevant area in each individual patient of an independently recorded dataset and achieved the same good accuracy as in our previous studies. The reproducibility of our results across datasets is promising for a multicentre study to test the clinical application of high frequency oscillations to guide epilepsy surgery.

scholarly journals Back to the Future? The Fallopian Tube, Precursor Escape and a Dualistic Model of High-Grade Serous Carcinogenesis

Cancers ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 468 ◽  
Author(s):  
T. Soong ◽  
David Kolin ◽  
Nathan Teschan ◽  
Christopher Crum
Keyword(s):  
Malignant Transformation ◽  
Fallopian Tube ◽  
Peritoneal Cavity ◽  
High Frequency ◽  
Low Frequency ◽  
High Grade ◽  
Fallopian Tubes ◽  
Advanced Malignancy ◽  
Cancer Susceptibility Genes ◽  
The Future

Beginning with the discovery of the BRCA-associated ovarian cancer susceptibility genes and subsequent detailed examination of risk-reducing salpingo-oophorectomy (RRSO) specimens, a new paradigm of ovarian carcinogenesis has unfolded with attention to the distal fallopian tube. The primary focus has been an early cancer or neoplasm in the fallopian tube which is seen in virtually all incidentally discovered high-grade serous cancers in asymptomatic women. This high-frequency of tubal involvement in early serous neoplasm (usually in the form of serous tubal intraepithelial carcinoma—STIC) has galvanized attention to this organ as a primary source of this disease. However, an enduring mystery has been the relatively low frequency of STIC in the fallopian tubes of women with advanced malignancy. This paradox, a high frequency of tubal involvement early on and a low frequency of involvement later in the disease process, has spurred interest in other potential sources, such as the ovarian surface epithelium or cortical inclusions and the secondary Mullerian system. However, because essentially all high-grade serous carcinomas are linked by TP53 mutations, and because fallopian tubes frequently contain early serous proliferations (ESPs) with these mutations, attention has turned to the possibility that the nonmalignant but TP53 mutated tubal epithelium could be responsible for an eventual malignancy. Recent data have shown evidence of a lineage continuity between ESPs and concurrent serous carcinomas prompting the concept of “precursor escape”. This creates a second component of the paradigm by which cells from early precursors are shed from the tube and undergo subsequent malignant transformation, emerging suddenly as widespread intraperitoneal malignancy. This dualistic model thus provides a unique pathway by which the future outcome (wide spread high-grade serous carcinomas—HGSC) is ultimately explained by going back in time to an early serous proliferation. This paradigm also brings the peritoneal cavity into focus, raising new questions about the potential co-variables or exposures that might facilitate the occasional malignant transformation of an ESP in the peritoneal cavity or on the peritoneal surface.

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