Journal articles on the topic 'High Frequency Oscillations (HFO)'
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1
Jacobs, Julia, Joyce Y. Wu, Piero Perucca, Rina Zelmann, Malenka Mader, Francois Dubeau, Gary W. Mathern, Andreas Schulze-Bonhage, and Jean Gotman. "Removing high-frequency oscillations." Neurology 91, no. 11 (August 17, 2018): e1040-e1052. http://dx.doi.org/10.1212/wnl.0000000000006158.
Abstract:
ObjectiveTo evaluate the use of interictal high-frequency oscillations (HFOs) in epilepsy surgery for prediction of postsurgical seizure outcome in a prospective multicenter trial.MethodsWe hypothesized that a seizure-free outcome could be expected in patients in whom the surgical planning included the majority of HFO-generating brain tissue while a poor seizure outcome could be expected in patients in whom only a few such areas were planned to be resected. Fifty-two patients were included from 3 tertiary epilepsy centers during a 1-year period. Ripples (80–250 Hz) and fast ripples (250–500 Hz) were automatically detected during slow-wave sleep with chronic intracranial EEG in 2 centers and acute intraoperative electrocorticography in 1 patient.ResultsThere was a correlation between the removal of HFO-generating regions and seizure-free outcome at the group level for all patients. No correlation was found, however, for the center-specific analysis, and an individual prognostication of seizure outcome was true in only 36 patients (67%). Moreover, some patients became seizure-free without removal of the majority of HFO-generating tissue. The investigation of influencing factors, including comparisons of visual and automatic analysis, using a threshold analysis for areas with high HFO activity, and excluding contacts bordering the resection, did not result in improved prognostication.ConclusionsOn an individual patient level, a prediction of outcome was not possible in all patients. This may be due to the analysis techniques used. Alternatively, HFOs may be less specific for epileptic tissue than earlier studies have indicated.
2
Chen, Zhuying, Matias I. Maturana, Anthony N. Burkitt, Mark J. Cook, and David B. Grayden. "High-Frequency Oscillations in Epilepsy." Neurology 96, no. 9 (January 6, 2021): 439–48. http://dx.doi.org/10.1212/wnl.0000000000011465.
Abstract:
For the past 2 decades, high-frequency oscillations (HFOs) have been enthusiastically studied by the epilepsy community. Emerging evidence shows that HFOs harbor great promise to delineate epileptogenic brain areas and possibly predict the likelihood of seizures. Investigations into HFOs in clinical epilepsy have advanced from small retrospective studies relying on visual identification and correlation analysis to larger prospective assessments using automatic detection and prediction strategies. Although most studies have yielded promising results, some have revealed significant obstacles to clinical application of HFOs, thus raising debate about the reliability and practicality of HFOs as clinical biomarkers. In this review, we give an overview of the current state of HFO research and pinpoint the conceptual and methodological issues that have hampered HFO translation. We highlight recent insights gained from long-term data, high-density recordings, and multicenter collaborations and discuss the open questions that need to be addressed in future research.
3
Matsumoto, Andrew, Benjamin H. Brinkmann, S. Matthew Stead, Joseph Matsumoto, Michal T. Kucewicz, W. Richard Marsh, Frederic Meyer, and Gregory Worrell. "Pathological and physiological high-frequency oscillations in focal human epilepsy." Journal of Neurophysiology 110, no. 8 (October 15, 2013): 1958–64. http://dx.doi.org/10.1152/jn.00341.2013.
Abstract:
High-frequency oscillations (HFO; gamma: 40–100 Hz, ripples: 100–200 Hz, and fast ripples: 250–500 Hz) have been widely studied in health and disease. These phenomena may serve as biomarkers for epileptic brain; however, a means of differentiating between pathological and normal physiological HFO is essential. We categorized task-induced physiological HFO during periods of HFO induced by a visual or motor task by measuring frequency, duration, and spectral amplitude of each event in single trial time-frequency spectra and compared them to pathological HFO similarly measured. Pathological HFO had higher mean spectral amplitude, longer mean duration, and lower mean frequency than physiological-induced HFO. In individual patients, support vector machine analysis correctly classified pathological HFO with sensitivities ranging from 70–98% and specificities >90% in all but one patient. In this patient, infrequent high-amplitude HFO were observed in the motor cortex just before movement onset in the motor task. This finding raises the possibility that in epileptic brain physiological-induced gamma can assume higher spectral amplitudes similar to those seen in pathologic HFO. This method if automated and validated could provide a step towards differentiating physiological HFO from pathological HFO and improving localization of epileptogenic brain.
4
DeWeese, E. L., T. Y. Sullivan, and P. L. Yu. "Ventilatory response to high-frequency airway oscillation in humans." Journal of Applied Physiology 58, no. 4 (April 1, 1985): 1099–106. http://dx.doi.org/10.1152/jappl.1985.58.4.1099.
Abstract:
To investigate respiratory control during high-frequency oscillation (HFO), ventilation was monitored in conscious humans by respiratory inductive plethysmography during application at the mouth of high-frequency pressure oscillations. Studies were conducted before and after airway and pharyngeal anesthesia. During HFO, breathing became slow and deep with an increase in tidal volume (VT) of 37% (P less than 0.01) and inspiratory duration (TI) of 34% (P less than 0.01). Timing ratio (TI/TT) increased 14% (P less than 0.05) and respiratory frequency (f) decreased 12% (P less than 0.01). Mean inspiratory flow (VT/TI) did not change during HFO. Following airway anesthesia, VT increased only 26% during HFO (P less than 0.01), whereas significant changes in TI, TI/TT, and f were not observed. Pharyngeal anesthesia failed to diminish the effect of HFO on TI, TT, or f, although the increase in VT was reduced. These results indicate that 1) HFO presented in this manner alters inspiratory timing without affecting the level of inspiratory activity, and 2) receptors in the larynx and/or lower airways may in part mediate the response.
5
Freitag, L., W. M. Long, C. S. Kim, and A. Wanner. "Removal of excessive bronchial secretions by asymmetric high-frequency oscillations." Journal of Applied Physiology 67, no. 2 (August 1, 1989): 614–19. http://dx.doi.org/10.1152/jappl.1989.67.2.614.
Abstract:
The present study evaluated whether high-frequency oscillations (HFO) with biased flow profiles applied at the airway opening are capable of altering mucus clearance. In eight anesthetized sheep, artificial mucus (100 P) was infused continuously (1 ml/min) into the left main bronchus via a cannula inserted through the dorsal wall of the left main bronchus after thoracotomy. Outcoming mucus was collected every 10 min from the end of a cuffed orotracheal tube. Animals were ventilated with a Harvard respirator at a low frequency with superimposed HFO at 14 Hz with asymmetrical waveforms generated by a digitally controlled electromagnetic piston pump (expiratory bias: peak expiratory flow 3.8 l/s, peak inspiratory flow 1.3 l/s; inspiratory bias: reverse of expiratory bias). The influence of posture and of HFO airflow bias on mucus clearance was determined. In the horizontal position, mucus clearance with expiratory biased HFO was 3.5 +/- 2 (SD) ml/10 min. Head-down tilt produced a clearance of 3.1 +/- 3 ml/10 min; addition of HFO with expiratory bias increased clearance to 11.0 +/- 2.0 ml/10 min (P less than 0.05). No clearance occurred with inspiratory biased HFO during head-down tilt. These results indicate that expiratory biased HFO at the airway opening can clear excessive airway secretions and augment clearance by postural drainage.
6
Pearce, Allison, Drausin Wulsin, Justin A. Blanco, Abba Krieger, Brian Litt, and William C. Stacey. "Temporal changes of neocortical high-frequency oscillations in epilepsy." Journal of Neurophysiology 110, no. 5 (September 1, 2013): 1167–79. http://dx.doi.org/10.1152/jn.01009.2012.
Abstract:
High-frequency (100–500 Hz) oscillations (HFOs) recorded from intracranial electrodes are a potential biomarker for epileptogenic brain. HFOs are commonly categorized as ripples (100–250 Hz) or fast ripples (250–500 Hz), and a third class of mixed frequency events has also been identified. We hypothesize that temporal changes in HFOs may identify periods of increased the likelihood of seizure onset. HFOs (86,151) from five patients with neocortical epilepsy implanted with hybrid (micro + macro) intracranial electrodes were detected using a previously validated automated algorithm run over all channels of each patient's entire recording. HFOs were characterized by extracting quantitative morphologic features and divided into four time epochs (interictal, preictal, ictal, and postictal) and three HFO clusters (ripples, fast ripples, and mixed events). We used supervised classification and nonparametric statistical tests to explore quantitative changes in HFO features before, during, and after seizures. We also analyzed temporal changes in the rates and proportions of events from each HFO cluster during these periods. We observed patient-specific changes in HFO morphology linked to fluctuation in the relative rates of ripples, fast ripples, and mixed frequency events. These changes in relative rate occurred in pre- and postictal periods up to thirty min before and after seizures. We also found evidence that the distribution of HFOs during these different time periods varied greatly between individual patients. These results suggest that temporal analysis of HFO features has potential for designing custom seizure prediction algorithms and for exploring the relationship between HFOs and seizure generation.
7
Ward, H. E., J. Armengol, and R. L. Jones. "Ventilation by external high-frequency oscillation in cats." Journal of Applied Physiology 58, no. 4 (April 1, 1985): 1390–99. http://dx.doi.org/10.1152/jappl.1985.58.4.1390.
Abstract:
Eight anesthetized tracheostomized cats were placed in an 8.2-liter airtight chamber with the trachea connected to the exterior. Thirty-two combinations of high-frequency oscillations (HFO) (0.5–30 Hz; 25–100 ml) were delivered for 10 min each in random order into the chamber. Arterial blood gas tensions during oscillation were compared with control measurements made after 10 min of spontaneous breathing without oscillation when the mean arterial PCO2 (PaCO2) was 30.1 Torr. Ventilation due to spontaneous breathing (Vs) and oscillation (Vo) were derived from the chamber pressure trace and a pneumotachograph, respectively. As the oscillation frequency increased, oscillated tidal volume (Vo) decreased from a mean of 39 (0.5 Hz) to 3.3 ml (30 Hz) when 100 ml was delivered to the chamber. From 6–25 Hz, apnea occurred with Vo less than estimated respiratory dead space (VD); the minimum effective Vo/VD ratio was 0.37 +/- 0.05. Although Vo was maximal at 10 Hz at each oscillation volume, the lowest PaCO2 occurred at 2–6 Hz, and arterial PO2 rose as expected during hypocapnia. Above 10 Hz, PaCO2 was determined by Vo and was independent of frequency, whereas at lower frequencies, PaCO2 was related to Vo; below 6 Hz, PaCO2 varied inversely with the calculated alveolar ventilation. As oscillations became more effective, both PaCO2 and Vs fell progressively and were highly correlated; apnea occurred when PaCO2 was reduced by a mean of 4.5 Torr. Mean chamber pressure remained near zero up to 15 Hz, indicating functional residual capacity did not change. We conclude that externally applied HFO can readily maintain gas exchange in vivo, with Vo less than VD at frequencies over 2 Hz.
8
Mochizuki, Hitoshi, and Yoshikazu Ugawa. "High-Frequency Oscillations in Somatosensory System." Clinical EEG and Neuroscience 36, no. 4 (October 2005): 278–84. http://dx.doi.org/10.1177/155005940503600407.
Abstract:
The recent revival of interest in high-frequency oscillation (HFO) is triggered by getting an opportunity to noninvasively monitor the timing of highly synchronized and rapidly repeating population spikes generated in the human somatosensory system. HFOs could be recorded from brainstem, cuneothalamic relay neurons, thalamus, thalamocortical radiation, thalamocortical terminals and cortex with deep brain or surface electrodes, or with magnetoencephalography. Here we briefly review the HFOs at each level of somatosensory pathways. HFOs recorded at brainstem might be produced by volume conduction from oscillations of the medial lemniscus. Thalamic HFOs at around 1000 Hz frequency would be generated within the somatosensory thalamus. Cortical HFOs would be generated by at least a few different mechanisms, thalamocortical projection terminals, interneurons and pyramidal cells of the primary sensory cortex. HFOs have been studied in several ways: their modulation by arousal changes, movements or drugs, their recovery function, effects of transcranial magnetic stimulation on them and also their changes in patients with various neurological diseases.
9
Plenz, D., and S. T. Kitai. "Generation of high-frequency oscillations in local circuits of rat somatosensory cortex cultures." Journal of Neurophysiology 76, no. 6 (December 1, 1996): 4180–84. http://dx.doi.org/10.1152/jn.1996.76.6.4180.
Abstract:
1. Rhythmic cortical activity was investigated with intracellular recordings in cortex-striatum-mesencephalon organotypic cultures grown for 42 +/- 3 (SE) days in vitro. 2. Electrical stimulation of supragranular layers induced a self-sustained high-frequency oscillation (HFO) in pyramidal neurons and interneurons. 3. The HFO started 197 +/- 39 ms after stimulation and had a mean duration of 1.0 +/- 0.2 s and an initial frequency of 38 +/- 2 Hz. A decrease in frequency at a rate of 11.5 +/- 2.7 Hz/s started on average 547 +/- 109 ms after the onset of the HFO. 4. During the HFO, local interneurons and pyramidal neurons synchronized their activities. The synaptic origin of the HFO was confirmed by its reversal potential at -57 +/- 4 mV. 5. These results suggest that a self-maintained HFO can be induced in local cortical circuits by excitation of supragranular layers. This HFO would facilitate synchronization between distant cortical and thalamic regions.
10
Spampanato, Jay, and Istvan Mody. "Spike Timing of Lacunosom-Moleculare Targeting Interneurons and CA3 Pyramidal Cells During High-Frequency Network Oscillations In Vitro." Journal of Neurophysiology 98, no. 1 (July 2007): 96–104. http://dx.doi.org/10.1152/jn.00188.2007.
Abstract:
Network activity in the 200- to 600-Hz range termed high-frequency oscillations (HFOs) has been detected in epileptic tissue from both humans and rodents and may underlie the mechanism of epileptogenesis in experimental rodent models. Slower network oscillations including theta and gamma oscillations as well as ripples are generated by the complex spike timing and interactions between interneurons and pyramidal cells of the hippocampus. We determined the activity of CA3 pyramidal cells, stratum oriens lacunosum-moleculare (O-LM) and s. radiatum lacunosum-moleculare (R-LM) interneurons during HFO in the in vitro low-Mg2+ model of epileptiform activity in GIN mice. In these animals, interneurons can be identified prior to cell-attached recordings by the expression of green-fluorescent protein (GFP). Simultaneous local field potential recordings from s. pyramidale and on-cell recordings of individual interneurons and principal cells revealed three primary firing behaviors of the active cells: 36% of O-LM interneurons and 60% of pyramidal cells fired action potentials at high frequencies during the HFO. R-LM interneurons were biphasic in that they fired at high frequency at the beginning of the HFO but stopped firing before its end. When considering only the highest frequency component of the oscillations most pyramidal cells fired on the rising phase of the oscillation. These data provide evidence for functional distinction during HFOs within otherwise homogeneous groups of O-LM interneurons and pyramidal cells.
11
Allen, J. L., I. D. Frantz, and J. J. Fredberg. "Heterogeneity of mean alveolar pressure during high-frequency oscillations." Journal of Applied Physiology 62, no. 1 (January 1, 1987): 223–28. http://dx.doi.org/10.1152/jappl.1987.62.1.223.
Abstract:
Mean alveolar pressure may exceed mean airway pressure during high-frequency oscillations (HFO). To assess the magnitude of this effect and its regional heterogeneity, we studied six excised dog lungs during HFO [frequency (f) 2–32 Hz; tidal volume (VT) 5–80 ml] at transpulmonary pressures (PL) of 6, 10, and 25 cmH2O. We measured mean pressure at the airway opening (Pao), trachea (Ptr), and four alveolar locations (PA) using alveolar capsules. Pao was measured at the oscillator pump, wherein the peak dynamic head was less than 0.2 cmH2O. Since the dynamic head was negligible here, and since these were excised lungs, Pao thus represented true applied transpulmonary pressure. Ptr increasingly underestimated Pao as f and VT increased, with Pao - Ptr approaching 8 cmH2O. PA (averaged over all locations) and Pao were nearly equal at all PL's, f's, and VT's, except at PL of 6, f 32 Hz, and VT 80 ml, where (PA - Pao) was 3 cmH2O. Remarkably, mean pressure in the base exceeded that in the apex increasingly as f and VT increased, the difference approaching 3 cmH2O at high f and VT. We conclude that, although global alveolar overdistension assessed by PA - Pao is small during HFO under these conditions, larger regional heterogeneity in PA's exists that may be a consequence of airway branching angle asymmetry and/or regional flow distribution.
12
Goddon, Sven, Yuji Fujino, Jonathan M. Hromi, and Robert M. Kacmarek. "Optimal Mean Airway Pressure during High-frequency Oscillation." Anesthesiology 94, no. 5 (May 1, 2001): 862–69. http://dx.doi.org/10.1097/00000542-200105000-00026.
Abstract:
Background A number of groups have recommended setting positive end-expiratory pressure during conventional mechanical ventilation in adults at 2 cm H2O above the lower corner pressure (P(CL)) of the inspiratory pressure-volume (P-V) curve of the respiratory system. No equivalent recommendations for the setting of the mean airway pressure (Paw) during high-frequency oscillation (HFO) exist. The authors questioned if the Paw resulting in the best oxygenation without hemodynamic compromise during HFO is related to the static P-V curve in a large animal model of acute respiratory distress syndrome. Methods Saline lung lavage was performed in seven sheep (28+/-5 kg, mean +/- SD) until the arterial oxygen partial pressure/fraction of inspired oxygen ratio decreased to 85+/-27 mmHg at a positive end-expiratory pressure of 5 cm H2O (initial injury). The PCL (20+/-1 cm H2O) on the inflation limb and the point of maximum curvature change (PMC; 26+/-1 cm H2O) on the deflation limb of the static P-V curve were determined. The sheep were subjected to four 1-h cycles of HFO at different levels of Paw (P(CL) + 2, + 6, + 10, + 14 cm H2O), applied in random order. Each cycle was preceded by a recruitment maneuver at a sustained Paw of 50 cm H2O for 60 s. Results High-frequency oscillation with a Paw of 6 cm H2O above P(CL) (P(CL) + 6) resulted in a significant improvement in oxygenation (P < 0.01 vs. initial injury). No further improvement in oxygenation was observed with higher Paw, but cardiac output decreased, pulmonary vascular resistance increased, and oxygen delivery decreased at Paw greater than P(CL) + 6. The PMC on the deflation limb of the P-V curve was equal to the P(CL) + 6 (r = 0.77, P < 0.05). Conclusion In this model of acute respiratory distress syndrome, optimal Paw during HFO is equal to P(CL) + 6, which correlates with the PMC.
13
Webber, C. L. "High-frequency oscillations within early and late phases of the phrenic neurogram." Journal of Applied Physiology 66, no. 2 (February 1, 1989): 886–93. http://dx.doi.org/10.1152/jappl.1989.66.2.886.
Abstract:
Spectral analyses were performed on phrenic neurogram recordings from 18 cats to identify high-frequency oscillations (HFOs) inherent in the signals at different phases of inspiratory activity. Gating the analysis for the entire inspiratory phase resulted in dual spectral HFOs (27 and 83 Hz), both of which persisted when the analysis was repeated on the later phase of phrenic inspiratory activity alone (29 and 82 Hz). A third pass at the same data, gating for just the early phase of phrenic discharge, however, resulted in single spectral HFOs at the higher frequency only (86 Hz). Because both early and late recruited phrenic motoneurons carry both higher and lower spectral frequencies, these results demonstrate that the lower frequency HFO is distinctly delayed in onset compared with the higher frequency HFO, the latter of which is believed to have a brain stem origin. This delayed onset may be important in identifying the source of the lower frequency HFO, which appears to be specific to various respiratory efferent systems.
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Huang, W. X., M. I. Cohen, Q. Yu, W. R. See, and Q. He. "High-frequency oscillations in membrane potentials of medullary inspiratory and expiratory neurons (including laryngeal motoneurons)." Journal of Neurophysiology 76, no. 3 (September 1, 1996): 1405–12. http://dx.doi.org/10.1152/jn.1996.76.3.1405.
Abstract:
1. In midcollicular decerebrate, unanesthetized, paralyzed cats ventilated with a cycle-triggered pump system, the properties of high-frequency oscillations (HFOs, 50-100 Hz) in membrane potentials (MPs) of medullary inspiratory (I) and expiratory (E) cells were studied. Simultaneous recordings were taken from bilateral phrenic and recurrent laryngeal (RL) nerves and from cells in the intermediate ventral respiratory group (intVRG, 0-1 mm rostral to the obex) or the caudal ventral respiratory group (cVRG, 2-4 mm caudal to the obex). 2. Spectral coherence analyses were used to detect the presence of HFOs during I in I and E cell MPs. Cross-correlation histograms (CCHs) between the cell and phrenic signals were used to ascertain cell-nerve HFO phase relations and to identify cells as RL motoneurons. Of the 103 cells that had significant HFOs (cell-phrenic coherences > or = 0.1), measurable HFO peak lags in the CCH were seen in 53 cells: 1) RL cells (9 I cells and 7 E cells); and 2) other types of cell (8 intVRG I cells, 18 intVRG E cells, and 11 cVRG E cells). These cells had high HFO correlations; the cell-phrenic coherence range was 0.35-0.94, with a mean HFO frequency of 58 Hz. 3. The cell-phrenic HFO lag (in ms) was measured in the CCH as the lag of the primary peak (peak located nearest to 0 lag). The phase lag was defined as (lag of primary peak in ms)/(HFO period in ms). The phase lags differed markedly between two subsets of cells: 1) RL I cells had HFO depolarization peaks that lagged the phrenic HFO peaks (average cell-phrenic phase lag = -0.18); and 2) the non-RL cells, regardless of location (intVRG or cVRG) and type (I or E), had HFO depolarization peaks leading (preceding) the phrenic HFO peaks (average cell-phrenic phase lag = 0.28). In addition, the cVRG E cells had significantly shorter cell-phrenic phase lags than the intVRG E cells (0.23 vs. 0.31, respectively). 4. These lags can be compared with the (I unit)-phrenic phase lags (average approximately 0.3) found in earlier extracellular studies. 1) There is a transmission delay of about one half HFO cycle from excitatory I cells to RL I cells. 2) Because a depolarization peak in the MP of an E cell corresponds to the start of a hyperpolarizing wave, the excitatory bulbospinal pathways from I cells have transmission times comparable with those of the inhibitory intramedullary pathways from I cells to E cells. 5. These results indicate that study of HFO phase relations can furnish useful information on functional connectivity of medullary respiratory neurons during the I phase.
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István, Mihály, Bod Réka-Barbara, Orbán-Kis Károly, Berki Ádám-József, and Szilágyi Tibor. "The Effect of Deep Brain Stimulation on High Frequency Oscillations in a Chronic Epilepsy Model." Bulletin of Medical Sciences 93, no. 2 (December 1, 2020): 63–70. http://dx.doi.org/10.2478/orvtudert-2020-0014.
Abstract:
Abstract Temporal lobe epilepsy (TLE) is a severe neurological disease which is often pharmacoresistant. Deep brain stimulation (DBS) is a novel method for treating epilepsy; however, its mechanism of action is not fully understood. We aimed to study the effect of amygdala DBS in the pilocarpine model of TLE. Status epilepticus was induced by pilocarpine in male Wistar rats, and spontaneous seizures occurred after a latency period. A stimulating electrode was inserted into the left basolateral amygdala and two recording electrodes into the left and right hippocampus. A stimulus package consisted of 0.1 ms-long biphasic pulses applied regularly at 4 Hz for 50 seconds. This package was repeated four times a day, with 5-minute pauses, for 10 days. We also used an age-matched healthy control group of stimulated animals and another one of sham-operated rats. From the hippocampal local field potentials high frequency oscillations (HFOs) were analyzed as these are promising epilepsy biomarkers. HFOs are short oscillatory events between 80-600 Hz which were detected offline using an open-source application of MATLAB, the RIPPLELAB system. We found that the HFO rate was significantly higher in pilocarpine-treated rats compared to the control groups (0.41 ± 0.14 HFO/min vs. 0.006 ± 0.003 in the stimulated control group and no HFO in the sham-operated group). In the pilocarpine group an instantaneous decrease in HFO rate was observed while the stimulation was on (0.44 ± 0.15 HFO/min vs 0.07 ± 0.03 HFO/min, p=0.017). The effect was short-lived because the frequency of HFOs did not change significantly in the time windows between stimulus packages or during the ten-day stimulation period. The difference of HFO rates between epileptic and control groups could be used in the electrographic assessment of epilepsy. The decreased frequency of HFOs during stimulation may be useful to study the efficacy of DBS.
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Haufler, Darrell, and Denis Pare. "High-frequency oscillations are prominent in the extended amygdala." Journal of Neurophysiology 112, no. 1 (July 1, 2014): 110–19. http://dx.doi.org/10.1152/jn.00107.2014.
Abstract:
Previously, it was reported that various cortical and subcortical structures display high-frequency local field potential (LFP) oscillations in the 110- to 160-Hz range (HFOs), distinct from sharp-wave ripples. In the present study, we characterize HFOs in the extended amygdala. Rats were implanted with tetrode bundles in the bed nucleus of the stria terminalis (BNST), central amygdala (CeA), as well as adjacent regions (pallidum, caudate-putamen, and lateral septum). At all recorded sites, HFO power showed a systematic dependence on behavioral state: highest during quiet wakefulness, intermediate during paradoxical sleep, and lowest during active waking or slow-wave sleep. CO2 asphyxiation as well as anesthesia with isoflurane or urethane abolished HFOs. HFOs stood out relative to all other fast-frequency LFP components because they were highly coherent between distant sites of the extended amygdala, ipsi- and contralaterally. HFOs affected neuronal firing in two ways: firing rate could vary as a function of HFO power (rate modulation) or HFOs could entrain firing on a cycle-to-cycle basis (phase modulation). The incidence of phase-modulated neurons was about twice higher in BNST and CeA (20–40%) than in adjacent regions (≤8%). Among BNST and CeA neurons, many more were phase-modulated than rate-modulated, although about half of the latter were also phase-modulated. Overall, these results indicate that HFOs entrain the activity of a high proportion of neurons in the extended amygdala. A major challenge for future studies will be to identify the mechanisms supporting the high coherence of HFOs within and across hemispheres.
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Peng, Syu-Jyun, Chien-Chen Chou, Hsiang-Yu Yu, Chien Chen, Der-Jen Yen, Shang-Yeong Kwan, Sanford P. C. Hsu, Chun-Fu Lin, Hsin-Hung Chen, and Cheng-Chia Lee. "Ictal networks of temporal lobe epilepsy: views from high-frequency oscillations in stereoelectroencephalography." Journal of Neurosurgery 131, no. 4 (October 2019): 1086–194. http://dx.doi.org/10.3171/2018.6.jns172844.
Abstract:
OBJECTIVEIn this study, the authors investigated high-frequency oscillation (HFO) networks during seizures in order to determine how HFOs spread from the focal cerebral cortex and become synchronized across various areas of the brain.METHODSAll data were obtained from stereoelectroencephalography (SEEG) signals in patients with drug-resistant temporal lobe epilepsy (TLE). The authors calculated intercontact cross-coefficients between all pairs of contacts to construct HFO networks in 20 seizures that occurred in 5 patients. They then calculated HFO network topology metrics (i.e., network density and component size) after normalizing seizure duration data by dividing each seizure into 10 intervals of equal length (labeled I1–I10).RESULTSFrom the perspective of the dynamic topologies of cortical and subcortical HFO networks, the authors observed a significant increase in network density during intervals I5–I10. A significant increase was also observed in overall energy during intervals I3–I8. The results of subnetwork analysis revealed that the number of components continuously decreased following the onset of seizures, and those results were statistically significant during intervals I3–I10. Furthermore, the majority of nodes were connected to a single dominant component during the propagation of seizures, and the percentage of nodes within the largest component grew significantly until seizure termination.CONCLUSIONSThe consistent topological changes that the authors observed suggest that TLE is affected by common epileptogenic patterns. Indeed, the findings help to elucidate the epileptogenic network that characterizes TLE, which may be of interest to researchers and physicians working to improve treatment modalities for epilepsy, including resection, cortical stimulation, and neuromodulation treatments that are responsive to network topologies.
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Raju, V. Rama. "β-oscillations linked by neuronal-spiking in the STN via DBS of parkinson disease: Part – I." IP Indian Journal of Neurosciences 8, no. 3 (September 15, 2022): 167–71. http://dx.doi.org/10.18231/j.ijn.2022.035.
Abstract:
Typical head-worn brain surface (wired or wireless) EEG electrodes beta (β) band frequencies are amongst 13Hz to 30Hz. However, in the Parkinson`s the high beata frequency is between 20 Hz to 30 Hz. Atypical β-oscillations in BG were linked in the field of Patho physiology of Parkinson disease. 13Hz-30Hz β-oscillations into STN of Parkinson subjects has been verified to distress the spatio-temporal dynamics of high-frequency oscillations (HFOs) typically ranging from 200Hz–500Hz coupled with individual (single) neurons, probably and so hypothetically cooperating the functional litheness (or suppleness) of the motor-circuit. This study experimented the connections through concurrently gathering the field-potentials (i.e.,LFPs) plus single-unit-activity(SUA) from the parallelly connected basal-ganglion circuitry of 15 subjects (PD-patients) in deep-brain-stimulation(DBS) surgical-procedure of bilateral-STN. Stimulus phase-amplitude coupling (PAC) around nuclei was limited to β-phase plus HFO stimulus-amplitude. Coupling was greatest on the abaxial, i.e., dorsal- STN frontier-edge. Findings showed that greater β-HFO-PAC in close proximity (within the vicinity) macro-leads contact which were clinically useful evaluated by continuing un effective-contacts, implying that PAC could prognostic of retort to STN-DBS. Neural-spiking was confined to the shape of 7Hz–30Hz oscillations (/fluctuations in the membranes), then longitudinal-topo-graphy of spike-shape-locking(SSL)/ or spike-phase-locking(SPL) was analogous to PAC. Differences of PAC plus SSL/(SPL) indicated a lack—of spatio-temporal-correlations. β-coupled H.F.O.s and electrical-field protected (locked/fused) neurons have got unique and ideal phase-angles, i.e., signal/waveform-shapes above(+) x-axis and below (-) axis 2D spatio-temporal regions, didn`t transpired in the similar phase of modulating-oscillation. Hence, results yield further help which β-HFO-P.A.C might be key to pathos physiology of Parkinson which advises local electrical field-locked neurons are inadequate alone for the appearance of high frequency β-coupled oscillations.
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Alleyne, C. M., I. D. Frantz, and J. J. Fredberg. "Preferential axial flow during high-frequency oscillations: effects of gas density." Journal of Applied Physiology 66, no. 2 (February 1, 1989): 542–47. http://dx.doi.org/10.1152/jappl.1989.66.2.542.
Abstract:
Allen et al. (J. Clin. Invest. 76: 620–629, 1985) reported that regional phasic lung distension during high-frequency oscillations (HFO) is substantially and systemically heterogeneous when both frequency (f) and tidal volume (VT) are large. They hypothesized that this phenomenon was attributable to central airway geometry and preferential axial flow induced therein by the momentum flux of the inspiratory gas stream. According to that hypothesis, the observed distribution of phasic lung distension would depend on the ratio VT/VD* (where VD* is an index of anatomic dead space), independent of gas density (rho), when f is scaled in proportion to lung resonant frequency, fo. To test this hypothesis, we used the methods of Allen et al. (ibid.) to study six excised dog lungs during HFO (f = 2–32 Hz; VT = 5–80 ml) using gases of different densities. Alveolar pressure excursions (PA) were measured as rho spanned a 12-fold range using He, air, and SF6. The apex-to-base and right-to-left ratios of PA were used as indexes of regional heterogeneity of phasic lung distension. For each gas at low f, distension of the lung base was favored slightly independent of VT, but at higher f distension of the lung apex was favored when VT was small, whereas distension of the lung base was favored when VT was large. In addition, we observed substantial right-to-left differences in apical lobes during oscillation at high f not seen before.(ABSTRACT TRUNCATED AT 250 WORDS)
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Nunez, Michael D., Krit Charupanit, Indranil Sen-Gupta, Beth A. Lopour, and Jack J. Lin. "Beyond rates: time-varying dynamics of high frequency oscillations as a biomarker of the seizure onset zone." Journal of Neural Engineering 19, no. 1 (February 1, 2022): 016034. http://dx.doi.org/10.1088/1741-2552/ac520f.
Abstract:
Abstract Objective. High frequency oscillations (HFOs) recorded by intracranial electrodes have generated excitement for their potential to help localize epileptic tissue for surgical resection. However, the number of HFOs per minute (i.e. the HFO ‘rate’) is not stable over the duration of intracranial recordings; for example, the rate of HFOs increases during periods of slow-wave sleep. Moreover, HFOs that are predictive of epileptic tissue may occur in oscillatory patterns due to phase coupling with lower frequencies. Therefore, we sought to further characterize between-seizure (i.e. ‘interictal’) HFO dynamics both within and outside the seizure onset zone (SOZ). Approach. Using long-term intracranial EEG (mean duration 10.3 h) from 16 patients, we automatically detected HFOs using a new algorithm. We then fit a hierarchical negative binomial model to the HFO counts. To account for differences in HFO dynamics and rates between sleep and wakefulness, we also fit a mixture model to the same data that included the ability to switch between two discrete brain states that were automatically determined during the fitting process. The ability to predict the SOZ by model parameters describing HFO dynamics (i.e. clumping coefficients and coefficients of variation) was assessed using receiver operating characteristic curves. Main results. Parameters that described HFO dynamics were predictive of SOZ. In fact, these parameters were found to be more consistently predictive than HFO rate. Using concurrent scalp EEG in two patients, we show that the model-found brain states corresponded to (1) non-REM sleep and (2) awake and rapid eye movement sleep. However the brain state most likely corresponding to slow-wave sleep in the second model improved SOZ prediction compared to the first model for only some patients. Significance. This work suggests that delineation of SOZ with interictal data can be improved by the inclusion of time-varying HFO dynamics.
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Aspros, Alexander J., Claudia G. Coto, James F. Lewis, and Ruud A. W. Veldhuizen. "High-frequency oscillation and surfactant treatment in an acid aspiration model." Canadian Journal of Physiology and Pharmacology 88, no. 1 (January 2010): 14–20. http://dx.doi.org/10.1139/y09-096.
Abstract:
Both exogenous surfactant therapy and high-frequency oscillation (HFO) have been proposed as clinical interventions in acute respiratory distress syndrome (ARDS). The combination of these 2 interventions has not been studied in a relevant model of ARDS. It was hypothesized that surfactant treatment combined with HFO is superior to either surfactant treatment or HFO alone in a model of ARDS. Adult rats had lung injury induced by instillation of 0.1 mol/L HCl, followed by randomization to one of 4 groups: Conventional mechanical ventilation (CMV) + air (no treatment), CMV + surfactant, HFO + air, and HFO + surfactant. Oxygenation, lung compliance, surfactant, and cytokine concentrations in the lung lavage were analyzed. The results showed superior oxygenation in HFO ventilated animals regardless of surfactant treatment compared with CMV. Nonsurfactant-treated animals ventilated with HFO had a significantly greater proportion of large aggregates, and had greater lung compliance compared with non-surfactant-treated animals ventilated with CMV. Surfactant therapy combined with HFO provided no advantages with respect to these outcomes. These data suggest an advantage of HFO over CMV when exogenous surfactant was not given, and that surfactant treatment combined with HFO was not superior to HFO ventilation alone.
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Olszewski, Maciej, Joanna Piasecka, Sailaja A. Goda, Stefan Kasicki, and Mark J. Hunt. "Antipsychotic compounds differentially modulate high-frequency oscillations in the rat nucleus accumbens: a comparison of first- and second-generation drugs." International Journal of Neuropsychopharmacology 16, no. 5 (June 1, 2013): 1009–20. http://dx.doi.org/10.1017/s1461145712001034.
Abstract:
Abstract Improved understanding of the actions of antipsychotic compounds is critical for a better treatment of schizophrenia. Abnormal oscillatory activity has been found in schizophrenia and in rat models of the disease. N-Methyl-d-aspartic acid receptor (NMDAR) antagonists, used to model certain features of schizophrenia, increase the frequency and power of high-frequency oscillations (HFO, 130–180 Hz) in the rat nucleus accumbens, a brain region implicated in schizophrenia pathology. Antipsychotics can be classified as first- and second-generation drugs, the latter often reported to have wider benefit in humans and experimental models. This prompted the authors to examine the pre- and post-treatment effects of clozapine, risperidone (second-generation drugs) and sulpiride and haloperidol (first-generation drugs) on ketamine and MK801-enhanced accumbal HFO. Both NMDAR antagonists increased HFO frequency. In contrast, clozapine and risperidone markedly and dose-dependently reduced the frequency of spontaneous and NMDAR-antagonist-enhanced HFO, whilst a moderate effect was found for sulpiride and a much weaker effect for haloperidol. Unexpectedly, we found reductions in HFO frequency were associated with an increase in its power. These findings indicate that modulation of accumbal HFO frequency may be a fundamental effect produced by antipsychotic compounds. Of the drugs investigated, first- and second-generation compounds could be dissociated by their potency on this measure. This effect may partially explain the differences in the clinical profile of these drugs.
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Fuyuki, T., S. Suzuki, M. Sakurai, H. Sasaki, J. P. Butler, and T. Takishima. "Ventilatory effectiveness of high-frequency oscillation applied to the body surface." Journal of Applied Physiology 62, no. 6 (June 1, 1987): 2410–15. http://dx.doi.org/10.1152/jappl.1987.62.6.2410.
Abstract:
To determine the ventilatory effectiveness of high-frequency oscillation (HFO) at different sites on the body surface, we applied HFO separately to the abdomen, the rib cage, or the whole body in eight anesthetized and paralyzed dogs. Test frequencies were 5, 7, 9, and 11 Hz with tidal volume kept constant at 2.5 ml/kg. During HFO application to the abdomen, we observed significantly higher arterial O2 partial pressure (P less than 0.05) at 5, 7, and 9 Hz and lower arterial CO2 partial pressure (P less than 0.05) at 7, 9, and 11 Hz than with rib cage or whole-body HFO. There was no significant difference in blood gases between rib cage and whole-body HFO. Thus, using blood gases as an index of ventilatory effectiveness, the present study showed that HFO applied at the abdomen was the most effective of the three kinds of body surface HFO. In comparison to rib cage or whole-body application, abdominal HFO was accompanied by substantial paradoxical movement of the diaphragm and rib cage. The associated lung distortion may result in pendelluft, which in turn may be the mechanism for increased ventilatory effectiveness with abdominal application of HFO.
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Yin, Liyong, Fan Tian, Rui Hu, Zhaohui Li, and Fuzai Yin. "Estimating Phase Amplitude Coupling between Neural Oscillations Based on Permutation and Entropy." Entropy 23, no. 8 (August 18, 2021): 1070. http://dx.doi.org/10.3390/e23081070.
Abstract:
Cross-frequency phase–amplitude coupling (PAC) plays an important role in neuronal oscillations network, reflecting the interaction between the phase of low-frequency oscillation (LFO) and amplitude of the high-frequency oscillations (HFO). Thus, we applied four methods based on permutation analysis to measure PAC, including multiscale permutation mutual information (MPMI), permutation conditional mutual information (PCMI), symbolic joint entropy (SJE), and weighted-permutation mutual information (WPMI). To verify the ability of these four algorithms, a performance test including the effects of coupling strength, signal-to-noise ratios (SNRs), and data length was evaluated by using simulation data. It was shown that the performance of SJE was similar to that of other approaches when measuring PAC strength, but the computational efficiency of SJE was the highest among all these four methods. Moreover, SJE can also accurately identify the PAC frequency range under the interference of spike noise. All in all, the results demonstrate that SJE is better for evaluating PAC between neural oscillations.
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Sitnikova, Evgenia, Dmitrii Perevozniuk, Elizaveta Rutskova, Shukhrat Uzakov, and Viktor A. Korshunov. "Reduction of Hippocampal High-Frequency Activity in Wag/Rij Rats with a Genetic Predisposition to Absence Epilepsy." Diagnostics 12, no. 11 (November 15, 2022): 2798. http://dx.doi.org/10.3390/diagnostics12112798.
Abstract:
In temporal lobe epilepsy, high frequency oscillations serve as electroencephalographic (EEG) markers of epileptic hippocampal tissue. In contrast, absence epilepsy and other idiopathic epilepsies are known to result from thalamo-cortical abnormalities, with the hippocampus involvement considered to be only indirect. We aimed to uncover the role of the hippocampus in absence epilepsy using a genetic rat model of absence epilepsy (WAG/Rij rats), in which spike-wave discharges (SWDs) appear spontaneously in cortical EEG. We performed simultaneous recordings of local field potential from the hippocampal dentate gyrus using pairs of depth electrodes and epidural cortical EEG in freely moving rats. Hippocampal ripples (100–200 Hz) and high frequency oscillations (HFO, 50–70 Hz) were detected using GUI RIPPLELAB in MatLab (Navarrete et al., 2016). Based on the dynamics of hippocampal ripples, SWDs were divided into three clusters, which might represent different seizure types in reference to the involvement of hippocampal processes. This might underlie impairment of hippocampus-related cognitive processes in some patients with absence epilepsy. A significant reduction to nearly zero-ripple-density was found 4–8 s prior to SWD onset and during 4 s immediately after SWD onset. It follows that hippocampal ripples were not just passively blocked by the onset of SWDs, but they were affected by spike-wave seizure initiation mechanisms. Hippocampal HFO were reduced during the preictal, ictal and postictal periods in comparison to the baseline. Therefore, hippocampal HFO seemed to be blocked with spike-wave seizures. All together, this might underlie impairment of hippocampus-related cognitive processes in some patients with absence epilepsy. Further investigation of processes underlying SWD-related reduction of hippocampal ripples and HFO oscillations may help to predict epileptic attacks and explain cognitive comorbidities in patients with absence epilepsy.
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Marchenko, Vitaliy, and Robert F. Rogers. "Temperature and state dependence of dynamic phrenic oscillations in the decerebrate juvenile rat." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 293, no. 6 (December 2007): R2323—R2335. http://dx.doi.org/10.1152/ajpregu.00472.2007.
Abstract:
The aim of the present study was to determine characteristics of fast oscillations in the juvenile rat phrenic nerve (Ph) and to establish their temperature and state dependence. Two different age-matched decerebrate, baro- and chemodenervated rat preparations, in vivo and in situ arterially perfused models, were used to examine three systemic properties: 1) generation and dynamics of fast oscillations in Ph activity (both preparations), 2) responses to anoxia (both preparations), and 3) the effects of temperature on fast oscillations (in situ only). Both juvenile preparations generated power and coherence in two major bands analogous to adult medium- and high-frequency oscillations (HFO) at frequencies that increased with temperature but were lower than in adults. At < 28°C, however, Ph oscillations were confined primarily to one low-frequency band (20–45 Hz). During sustained anoxia, both preparations produced stereotypical state changes from eupnea to hyperpnea to transition bursting (a behavior present only in vivo during incomplete ischemia) to gasping. Thus the juvenile rat produces a sequential pattern of responses to anoxia that are intermediate forms between those produced by neonates and those produced by adults. Time-frequency analysis determined that fast oscillations demonstrated dynamics over the course of the inspiratory burst and a state dependence similar to that of adults in vivo in which hyperpnea (and transition) bursts are associated with increases in HFO, while gasping contains no HFO. Our results confirm that both the fast oscillations in Ph activity and the coherence between Ph pairs produced by the juvenile rat are profoundly state- and temperature-dependent.
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Marchenko, Vitaliy, and Robert F. Rogers. "Selective loss of high-frequency oscillations in phrenic and hypoglossal activity in the decerebrate rat during gasping." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 291, no. 5 (November 2006): R1414—R1429. http://dx.doi.org/10.1152/ajpregu.00217.2006.
Abstract:
Respiratory motor outputs contain medium-(MFO) and high-frequency oscillations (HFO) that are much faster than the fundamental breathing rhythm. However, the associated changes in power spectral characteristics of the major respiratory outputs in unanesthetized animals during the transition from normal eupneic breathing to hypoxic gasping have not been well characterized. Experiments were performed on nine unanesthetized, chemo- and barodenervated, decerebrate adult rats, in which asphyxia elicited hyperpnea, followed by apnea and gasping. A gated fast Fourier transform (FFT) analysis and a novel time-frequency representation (TFR) analysis were developed and applied to whole phrenic and to medial branch hypoglossal nerve recordings. Our results revealed one MFO and one HFO peak in the phrenic output during eupnea, where HFO was prominent in the first two-thirds of the burst and MFO was prominent in the latter two-thirds of the burst. The hypoglossal activity contained broadband power distribution with several distinct peaks. During gasping, two high-amplitude MFO peaks were present in phrenic activity, and this state was characterized by a conspicuous loss in HFO power. Hypoglossal activity showed a significant reduction in power and a shift in its distribution toward lower frequencies during gasping. TFR analysis of phrenic activity revealed the increasing importance of an initial low-frequency “start-up” burst that grew in relative intensity as hypoxic conditions persisted. Significant changes in MFO and HFO rhythm generation during the transition from eupnea to gasping presumably reflect a reconfiguration of the respiratory network and/or alterations in signal processing by the circuitry associated with the two motor pools.
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Feyissa, Anteneh M., Gregory A. Worrell, William O. Tatum, Deependra Mahato, Benjamin H. Brinkmann, Steven S. Rosenfeld, Karim ReFaey, Perry S. Bechtle, and Alfredo Quinones-Hinojosa. "High-frequency oscillations in awake patients undergoing brain tumor-related epilepsy surgery." Neurology 90, no. 13 (February 28, 2018): e1119-e1125. http://dx.doi.org/10.1212/wnl.0000000000005216.
Abstract:
ObjectiveTo examine the relationship between high-frequency oscillations (HFOs) and the presence of preoperative seizures, World Health Organization tumor grade, and isocitrate dehydrogenase 1 (IDH1) mutational status in gliomas.MethodsWe retrospectively studied intraoperative electrocorticography recorded in 16 patients with brain tumor (12 presenting with seizures) who underwent awake craniotomy and surgical resection between September 2016 and June 2017. The number and distribution of HFOs were determined and quantified visually and with an automated HFO detector.ResultsFive patients had low-grade (1 with grade I and 4 with grade II) and 11 had high-grade (6 with grade III and 5 with grade IV) brain tumors. An IDH1 mutation was found in 6 patients. Patients with a history of preoperative seizures were more likely to have HFOs than those without preoperative seizures (9 of 12 vs 0 of 4, p = 0.02). The rate of HFOs was higher in patients with IDH1 mutant (mean 7.2 per minute) than IDH wild-type (mean 2.3 per minute) genotype (p = 0.03).ConclusionsHFOs are common in brain tumor-related epilepsy, and HFO rate may be a useful measure of epileptogenicity in gliomas. Our findings further support the notion that IDH1 mutant genotype is more epileptogenic than IDH1 wild-type genotype gliomas.
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Denny, Margaret, and Anne Smith. "Respiratory Control in Stuttering Speakers." Journal of Speech, Language, and Hearing Research 43, no. 4 (August 2000): 1024–37. http://dx.doi.org/10.1044/jslhr.4304.1024.
Abstract:
This study tested the hypothesis that, in stuttering speakers, relations between the neural control systems for speech and life support, or metabolic breathing, may differ from relations previously observed in normally fluent subjects. Bilaterally coherent high-frequency oscillations in inspiratory-related EMGs, measured as maximum coherence in the frequency band of 60–110 Hz (MC-HFO), were used as indicators of participation by the brainstem controller for metabolic breathing in 10 normally fluent and 10 stuttering speakers. In all controls and most stuttering subjects, MC-HFO for speech was higher than or comparable to MC-HFO for deep breathing. For 4 stuttering subjects, higher MC-HFO was observed for speech than for deep breathing. Comparison of deep breathing to a speechlike breathing task yielded similar results. No relationship between MC-HFO during speech and severity of disfluency was observed. We conclude that in some stuttering speakers, the relations between respiratory controllers are atypical, but that high participation by the HFO-producing circuitry in the brainstem during speech is not sufficient to disrupt fluency.
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Guragain, Hari, Jan Cimbalnik, Matt Stead, David M. Groppe, Brent M. Berry, Vaclav Kremen, Daniel Kenney-Jung, Jeffrey Britton, Gregory A. Worrell, and Benjamin H. Brinkmann. "Spatial variation in high-frequency oscillation rates and amplitudes in intracranial EEG." Neurology 90, no. 8 (January 24, 2018): e639-e646. http://dx.doi.org/10.1212/wnl.0000000000004998.
Abstract:
ObjectiveTo assess the variation in baseline and seizure onset zone interictal high-frequency oscillation (HFO) rates and amplitudes across different anatomic brain regions in a large cohort of patients.MethodsSeventy patients who had wide-bandwidth (5 kHz) intracranial EEG (iEEG) recordings during surgical evaluation for drug-resistant epilepsy between 2005 and 2014 who had high-resolution MRI and CT imaging were identified. Discrete HFOs were identified in 2-hour segments of high-quality interictal iEEG data with an automated detector. Electrode locations were determined by coregistering the patient's preoperative MRI with an X-ray CT scan acquired immediately after electrode implantation and correcting electrode locations for postimplant brain shift. The anatomic locations of electrodes were determined using the Desikan-Killiany brain atlas via FreeSurfer. HFO rates and mean amplitudes were measured in seizure onset zone (SOZ) and non-SOZ electrodes, as determined by the clinical iEEG seizure recordings. To promote reproducible research, imaging and iEEG data are made freely available (msel.mayo.edu).ResultsBaseline (non-SOZ) HFO rates and amplitudes vary significantly in different brain structures, and between homologous structures in left and right hemispheres. While HFO rates and amplitudes were significantly higher in SOZ than non-SOZ electrodes when analyzed regardless of contact location, SOZ and non-SOZ HFO rates and amplitudes were not separable in some lobes and structures (e.g., frontal and temporal neocortex).ConclusionsThe anatomic variation in SOZ and non-SOZ HFO rates and amplitudes suggests the need to assess interictal HFO activity relative to anatomically accurate normative standards when using HFOs for presurgical planning.
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Wozniak, J. A., P. W. Davenport, and P. C. Kosch. "Responses of pulmonary vagal mechanoreceptors to high-frequency oscillatory ventilation." Journal of Applied Physiology 65, no. 2 (August 1, 1988): 633–39. http://dx.doi.org/10.1152/jappl.1988.65.2.633.
Abstract:
The discharge of 57 slowly adapting pulmonary stretch receptors (PSR's) and 16 rapidly adapting receptors (RAR's) was recorded from thin vagal filaments in anesthetized dogs. The receptors were localized and separated into three groups: extrathoracic tracheal, intrathoracic tracheal, and intrapulmonary receptors. The influence of high-frequency oscillatory ventilation (HFO) at 29 Hz on receptor discharge was analyzed by separating the response to the associated shift in functional residual capacity (FRC) from the oscillatory component of the response. PSR activity during HFO was increased from spontaneous breathing (49%) and from the static FRC shift (25%). PSR activity during the static inflation was increased 19% over spontaneous breathing. RAR activity was also increased with HFO. These results demonstrate that 1) the increased activity of PSR and RAR during HFO is due primarily to the oscillating action of the ventilator and secondarily to the shift in FRC associated with HFO, 2) the increased PSR activity during HFO may account for the observed apneic response, and 3) PSR response generally decreases with increasing distance from the tracheal opening.
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Cai, Zhengxiang, Abbas Sohrabpour, Haiteng Jiang, Shuai Ye, Boney Joseph, Benjamin H. Brinkmann, Gregory A. Worrell, and Bin He. "Noninvasive high-frequency oscillations riding spikes delineates epileptogenic sources." Proceedings of the National Academy of Sciences 118, no. 17 (April 19, 2021): e2011130118. http://dx.doi.org/10.1073/pnas.2011130118.
Abstract:
High-frequency oscillations (HFOs) are a promising biomarker for localizing epileptogenic brain and guiding successful neurosurgery. However, the utility and translation of noninvasive HFOs, although highly desirable, is impeded by the difficulty in differentiating pathological HFOs from nonepileptiform high-frequency activities and localizing the epileptic tissue using noninvasive scalp recordings, which are typically contaminated with high noise levels. Here, we show that the consistent concurrence of HFOs with epileptiform spikes (pHFOs) provides a tractable means to identify pathological HFOs automatically, and this in turn demarks an epileptiform spike subgroup with higher epileptic relevance than the other spikes in a cohort of 25 temporal epilepsy patients (including a total of 2,967 interictal spikes and 1,477 HFO events). We found significant morphological distinctions of HFOs and spikes in the presence/absence of this concurrent status. We also demonstrated that the proposed pHFO source imaging enhanced localization of epileptogenic tissue by 162% (∼5.36 mm) for concordance with surgical resection and by 186% (∼12.48 mm) with seizure-onset zone determined by invasive studies, compared to conventional spike imaging, and demonstrated superior congruence with the surgical outcomes. Strikingly, the performance of spike imaging was selectively boosted by the presence of spikes with pHFOs, especially in patients with multitype spikes. Our findings suggest that concurrent HFOs and spikes reciprocally discriminate pathological activities, providing a translational tool for noninvasive presurgical diagnosis and postsurgical evaluation in vulnerable patients.
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Sedeek, Khaled A., Muneyuki Takeuchi, Klaudiusz Suchodolski, Sara O. Vargas, Motomu Shimaoka, Jay J. Schnitzer, and Robert M. Kacmarek. "Open-lung Protective Ventilation with Pressure Control Ventilation, High-frequency Oscillation, and Intratracheal Pulmonary Ventilation Results in Similar Gas Exchange, Hemodynamics, and Lung Mechanics." Anesthesiology 99, no. 5 (November 1, 2003): 1102–11. http://dx.doi.org/10.1097/00000542-200311000-00016.
Abstract:
Background Pressure control ventilation (PCV), high-frequency oscillation (HFO), and intratracheal pulmonary ventilation (ITPV) may all be used to provide lung protective ventilation in acute respiratory distress syndrome, but the specific approach that is optimal remains controversial. Methods Saline lavage was used to produce acute respiratory distress syndrome in 21 sheep randomly assigned to receive PCV, HFO, or ITPV as follows: positive end-expiratory pressure (PCV and ITPV) and mean airway pressure (HFO) were set in a pressure-decreasing manner after lung recruitment that achieved a ratio of Pao2/Fio2 > 400 mmHg. Respiratory rates were 30 breaths/min, 120 breaths/min, and 8 Hz, respectively, for PCV, ITPV, and HFO. Eucapnia was targeted with peak carinal pressure of no more than 35 cm H2O. Animals were then ventilated for 4 h. Results There were no differences among groups in gas exchange, lung mechanics, or hemodynamics. Tidal volume (PCV, 8.9 +/- 2.1 ml/kg; ITPV, 2.7 +/- 0.8 ml/kg; HFO, approximately 2.0 ml/kg) and peak carinal pressure (PCV, 30.6 +/- 2.6 cm H2O; ITPV, 22.3 +/- 4.8 cm H2O; HFO, approximately 24.3 cm H2O) were higher in PCV. Pilot histologic data showed greater interstitial hemorrhage and alveolar septal expansion in PCV than in HFO or ITPV. Conclusion These data indicate that HFO, ITPV, and PCV when applied with an open-lung protective ventilatory strategy results in the same gas exchange, lung mechanics, and hemodynamic response, but pilot data indicate that lung injury may be greater with PCV.
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Wu, Min, Ting Wan, Xiongbo Wan, Yuxiao Du, and Jinhua She. "Fast, Accurate Localization of Epileptic Seizure Onset Zones Based on Detection of High-Frequency Oscillations Using Improved Wavelet Transform and Matching Pursuit Methods." Neural Computation 29, no. 1 (January 2017): 194–219. http://dx.doi.org/10.1162/neco_a_00899.
Abstract:
This letter describes the improvement of two methods of detecting high-frequency oscillations (HFOs) and their use to localize epileptic seizure onset zones (SOZs). The wavelet transform (WT) method was improved by combining the complex Morlet WT with Shannon entropy to enhance the temporal-frequency resolution during HFO detection. And the matching pursuit (MP) method was improved by combining it with an adaptive genetic algorithm to improve the speed and accuracy of the calculations for HFO detection. The HFOs detected by these two methods were used to localize SOZs in five patients. A comparison shows that the improved WT method provides high specificity and quick localization and that the improved MP method provides high sensitivity.
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King, M., A. Zidulka, DM Phillips, D. Wight, D. Gross, and HK Chang. "Tracheal mucus clearance in high-frequency oscillation: effect of peak flow rate bias." European Respiratory Journal 3, no. 1 (January 1, 1990): 6–13. http://dx.doi.org/10.1183/09031936.93.03010006.
Abstract:
We have reported previously that high-frequency oscillation of the chest wall (HFO/CW) enhances the tracheal mucus clearance rate (TMCR) in dogs. This enhancement of TMCR may be due in part to the expiratory bias in peak flow rate (VE/VI greater than 1) that occurs during HFO/CW. We examined this factor in 8 anaesthetized, spontaneously breathing dogs by comparing TMCR during the following manoeuvers: 1) HFO/CW, applied by means of a thoracic cuff; 2) symmetric high-frequency oscillation via the airway opening (HFO/AO), applied by means of a piston pump driven by sinusoidal signal; 3) HFO/AO with an expiratory bias in peak flow, and 4) HFO/AO with an inspiratory bias in peak flow. All manoeuvers were of 5 min duration and were performed at 13 Hz and an oscillatory tidal volume of 1.5 ml.kg-1. In the latter two manoeuvers, the piston pump was driven by a nonsinusoidal signal such that peak VE/VI was greater than and less than unity, respectively. A high-impedance, cross-current flow of warmed, humidified air was provided at the tracheal tube. The order of manoeuvers 2, 3 and 4 was randomized, while manoeuver 1 was repeated at the end. TMCR was determined by direct bronchoscopic visualization of charcoal particle transport. Each HFO manoeuver was bracketed by a control period of spontaneous breathing. We found that TMCR during HFO/CW was 2.4 x control (p less than 0.001), in line with previous results.(ABSTRACT TRUNCATED AT 250 WORDS)
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Jacobs, Julia, and Maeike Zijlmans. "HFO to Measure Seizure Propensity and Improve Prognostication in Patients With Epilepsy." Epilepsy Currents 20, no. 6 (October 20, 2020): 338–47. http://dx.doi.org/10.1177/1535759720957308.
Abstract:
The study of high frequency oscillations (HFO) in the electroencephalogram (EEG) as biomarkers of epileptic activity has merely focused on their spatial location and relationship to the epileptogenic zone. It has been suggested in several ways that the amount of HFO at a certain point in time may reflect the disease activity or severity. This could be clinically useful in several ways, especially as noninvasive recording of HFO appears feasible. We grouped the potential hypotheses into 4 categories: (1) HFO as biomarkers to predict the development of epilepsy; (2) HFO as biomarkers to predict the occurrence of seizures; (3) HFO as biomarkers linked to the severity of epilepsy, and (4) HFO as biomarkers to evaluate outcome of treatment. We will review the literature that addresses these 4 hypotheses and see to what extent HFO can be used to measure seizure propensity and help determine prognosis of this unpredictable disease.
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Cha, E. J., E. Chow, H. K. Chang, and S. M. Yamashiro. "Lung hyperinflation in isolated dog lungs during high-frequency oscillation." Journal of Applied Physiology 65, no. 3 (September 1, 1988): 1172–79. http://dx.doi.org/10.1152/jappl.1988.65.3.1172.
Abstract:
To study the phenomenon of lung hyperinflation (LHI), i.e., an increase in lung volume without a concomitant rise in airway pressure, we measured lung volume changes in isolated dog lungs during high-frequency oscillation (HFO) with air, He, and SF6 and with mean tracheal pressure controlled at 2.5, 5.0, and 7.5 cmH2O. The tidal volume and frequency used were 1.5 ml/kg body wt and 20 Hz, respectively. LHI was observed during HFO in all cases except for a few trials with He. The degree of LHI was inversely related to mean tracheal pressure and varied directly with gas density. Maximum expiratory flow rate (Vmax) was measured during forced expiration induced by a vacuum source (-150 cmH2O) at the trachea. Vmax was consistently higher than the peak oscillatory flow rate (Vosc) during HFO, demonstrating that overall expiratory flow limitation did not cause LHI in isolated dog lungs. Asymmetry of inspiratory and expiratory impedances seems to be one cause of LHI, although other factors are involved.
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Ren, Guo-Ping, Jia-Qing Yan, Zhi-Xin Yu, Dan Wang, Xiao-Nan Li, Shan-Shan Mei, Jin-Dong Dai, et al. "Automated Detector of High Frequency Oscillations in Epilepsy Based on Maximum Distributed Peak Points." International Journal of Neural Systems 28, no. 01 (December 20, 2017): 1750029. http://dx.doi.org/10.1142/s0129065717500290.
Abstract:
High frequency oscillations (HFOs) are considered as biomarker for epileptogenicity. Reliable automation of HFOs detection is necessary for rapid and objective analysis, and is determined by accurate computation of the baseline. Although most existing automated detectors measure baseline accurately in channels with rare HFOs, they lose accuracy in channels with frequent HFOs. Here, we proposed a novel algorithm using the maximum distributed peak points method to improve baseline determination accuracy in channels with wide HFOs activity ranges and calculate a dynamic baseline. Interictal ripples (80–200[Formula: see text]Hz), fast ripples (FRs, 200–500[Formula: see text]Hz) and baselines in intracerebral EEGs from seven patients with intractable epilepsy were identified by experienced reviewers and by our computer-automated program, and the results were compared. We also compared the performance of our detector to four well-known detectors integrated in RIPPLELAB. The sensitivity and specificity of our detector were, respectively, 71% and 75% for ripples and 66% and 84% for FRs. Spearman’s rank correlation coefficient comparing automated and manual detection was [Formula: see text] for ripples and [Formula: see text] for FRs ([Formula: see text]). In comparison to other detectors, our detector had a relatively higher sensitivity and specificity. In conclusion, our automated detector is able to accurately calculate a dynamic iEEG baseline in different HFO activity channels using the maximum distributed peak points method, resulting in higher sensitivity and specificity than other available HFO detectors.
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Henderson, William R., Paolo B. Dominelli, Donald EG Griesdale, Daniel Talmor, and A. William Sheel. "Airway Pressure and Transpulmonary Pressure During High-Frequency Oscillation for Acute Respiratory Distress Syndrome." Canadian Respiratory Journal 21, no. 2 (2014): 107–11. http://dx.doi.org/10.1155/2014/163293.
Abstract:
BACKGROUND: High-frequency oscillation (HFO) is used for the treatment of refractory hypoxic respiratory failure.OBJECTIVE: To demonstrate that the mean transpulmonary pressure (PL) cannot be inferred from mean airway pressure (mPaw).METHODS: In seven patients already undergoing HFO for refractory acute respiratory distress syndrome, esophageal pressure (Pes) was measured using an esophageal balloon catheter. Pleural pressure (Ppl) and PLwere calculated from Pes.MAIN RESULTS: In the seven patients (mean [± SD] age 59±9 years) treated with HFO at 5±1 Hz and amplitude 75±10 cmH2O, the mPaw was 27±6 cmH2O, Ppl was 9±6 cmH2O and PLwas 18±11 cmH2O. Successful catheter placement and measurement of Pes occurred in 100% of subjects. There was no correlation between PLand mPaw. The majority of subjects required hemodynamic support during the use of HFO; the frequency and degree of support during the study period was no different than that before the study.CONCLUSION: The present report is the first to describe measuring Pes and calculating Ppl during HFO for acute respiratory distress syndrome. While both current guidelines and recent trials have titrated treatment based on mPaw and oxygenation, there is wide variability in PLduring HFO and PLcannot be predicted from mPaw.
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Wei, Shusheng, and Wusong Wen. "High-Frequency Oscillation of the Active-Bridge-Transformer-Based DC/DC Converter." Energies 15, no. 9 (May 2, 2022): 3311. http://dx.doi.org/10.3390/en15093311.
Abstract:
The dual-active-bridge converter (DAB) has attracted tremendous attention in recent years. However, its EMI issues, especially the high-frequency oscillation (HFO) induced by the dv/dt and parasitic elements of the transformer, are significant challenges. The multi-active-bridge converter (MAB) based on the multi-winding transformer also faces similar problems, which are even more complicated. This article investigates the HFO of active-bridge-transformer-based DC/DC converters including DAB and MAB. Firstly, the general HFO model is studied using the analysis of the AC equivalent circuit considering the asymmetrical parameters. Ignoring the AC resistance in the circuit, the high-order model of the voltage oscillation could be reduced to a second-order system. Based on the simplified model, the oscillation voltage generated by an active bridge is analyzed in the time domain. Then, a universal active voltage-oscillation-suppression method-selected harmonic-elimination phase-shift (SHE PS) modulation method is proposed. The impacts of the system parameters on the method are also revealed. The experimental results show the excellent performance of the proposed active suppression method, with voltage spike amplitude (VSA) reductions of 92.1% and 77.8% for the DAB and MAB prototypes, respectively.
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Marchenko, Vitaliy, and Robert F. Rogers. "Time-frequency coherence analysis of phrenic and hypoglossal activity in the decerebrate rat during eupnea, hyperpnea, and gasping." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 291, no. 5 (November 2006): R1430—R1442. http://dx.doi.org/10.1152/ajpregu.00218.2006.
Abstract:
Fast respiratory rhythms include medium- (MFO) and high-frequency oscillations (HFO), which are much faster than the fundamental breathing rhythm. According to previous studies, HFO is characterized by high coherence (Coh) in phrenic (Ph) nerve activity, thereby providing a means of distinguishing between these two types of oscillations. Changes in Coh between the Ph and hypoglossal (XII) nerves during the transition from normal eupnic breathing to gasping have not been characterized. Experiments were performed on nine unanesthetized, chemo- and barodenervated, decerebrate adult rats, in which sustained asphyxia elicited hyperpnea and gasping. A gated time-frequency Coh analysis was developed and applied to whole Ph and medial XII nerve recordings. The results showed dynamic Ph-Ph Coh during eupnea, including MFO and HFO. XII-XII Coh during eupnea was broadband and included four distinct peaks, with low-frequency Coh dominating the epochs preceding the onset of Ph activity. During gasping, only MFO-peaks were present in Ph-Ph Coh. Bilateral XII activity showed a significant reduction in Coh and a shift toward lower frequencies during gasping. In contrast, contralateral Ph-XII Coh progressively increased during state changes from eupnea to gasping, a tendency mirrored in the startup part of the Ph activity. These data suggest significant hypoxia/hypercapnia-induced alterations in synchronization between respiratory outputs during the transition from eupnea to gasping, reflecting a reconfiguration of the respiratory network and/or alterations in the circuitry associated with the motor pools, including dynamic coupling between outputs.
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Stacey, William C., Maciej T. Lazarewicz, and Brian Litt. "Synaptic Noise and Physiological Coupling Generate High-Frequency Oscillations in a Hippocampal Computational Model." Journal of Neurophysiology 102, no. 4 (October 2009): 2342–57. http://dx.doi.org/10.1152/jn.00397.2009.
Abstract:
There is great interest in the role of coherent oscillations in the brain. In some cases, high-frequency oscillations (HFOs) are integral to normal brain function, whereas at other times they are implicated as markers of epileptic tissue. Mechanisms underlying HFO generation, especially in abnormal tissue, are not well understood. Using a physiological computer model of hippocampus, we investigate random synaptic activity (noise) as a potential initiator of HFOs. We explore parameters necessary to produce these oscillations and quantify the response using the tools of stochastic resonance (SR) and coherence resonance (CR). As predicted by SR, when noise was added to the network the model was able to detect a subthreshold periodic signal. Addition of basket cell interneurons produced two novel SR effects: 1) improved signal detection at low noise levels and 2) formation of coherent oscillations at high noise that were entrained to harmonics of the signal frequency. The periodic signal was then removed to study oscillations generated only by noise. The combined effects of network coupling and synaptic noise produced coherent, periodic oscillations within the network, an example of CR. Our results show that, under normal coupling conditions, synaptic noise was able to produce gamma (30–100 Hz) frequency oscillations. Synaptic noise generated HFOs in the ripple range (100–200 Hz) when the network had parameters similar to pathological findings in epilepsy: increased gap junctions or recurrent synaptic connections, loss of inhibitory interneurons such as basket cells, and increased synaptic noise. The model parameters that generated these effects are comparable with published experimental data. We propose that increased synaptic noise and physiological coupling mechanisms are sufficient to generate gamma oscillations and that pathologic changes in noise and coupling similar to those in epilepsy can produce abnormal ripples.
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Burnos, S., O. Schmid, K. Niklaus, and J. Sarnthein. "P197. High-frequency oscillations (HFO, >500Hz) in the intraoperative somatosensory evoked potential (SEP)." Clinical Neurophysiology 126, no. 8 (August 2015): e150. http://dx.doi.org/10.1016/j.clinph.2015.04.248.
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Burnos, Sergey, Birgit Frauscher, Rina Zelmann, Claire Haegelen, Johannes Sarnthein, and Jean Gotman. "The morphology of high frequency oscillations (HFO) does not improve delineating the epileptogenic zone." Clinical Neurophysiology 127, no. 4 (April 2016): 2140–48. http://dx.doi.org/10.1016/j.clinph.2016.01.002.
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Marchenko, Vitaliy, and Robert F. Rogers. "GABAAergic and Glycinergic Inhibition in the Phrenic Nucleus Organizes and Couples Fast Oscillations in Motor Output." Journal of Neurophysiology 101, no. 4 (April 2009): 2134–45. http://dx.doi.org/10.1152/jn.91030.2008.
Abstract:
One of the characteristics of respiratory motor output is the presence of fast synchronous oscillations, at rates far exceeding the basic breathing rhythm, within a given functional population. However, the mechanisms responsible for organizing phrenic output into two dominant bands in vivo, medium (MFO)- and high (HFO)-frequency oscillations, have yet to be elucidated. We hypothesize that GABAAergic and glycinergic inhibition within the phrenic motor nucleus underlies the specific organization of these oscillations. To test this, the phrenic nuclei (C4) of 14 unanesthetized, decerebrate adult male Sprague-Dawley rats were microinjected unilaterally with either 4 mM strychnine ( n = 7) or GABAzine ( n = 7) to block glycine or GABAA receptors, respectively. Application of GABAzine caused an increase in overall phrenic amplitude during all three phases of respiration (inspiration, postinspiration, and expiration), while the increases caused by strychnine were most pronounced during postinspiration. Neither antagonist produced changes in inspiratory duration or respiratory rate. Power spectral analysis of inspiratory phrenic bursts showed that blockade of inhibition caused significant reduction in the relative power of MFO (GABAA and glycine receptors) and HFO (GABAA receptors only). In addition, analysis of the coherence between the firing of the ipsi- and contralateral phrenic nerves revealed that HFO coupling was significantly reduced by both antagonists and that of MFO was significantly reduced only by strychnine. We conclude that both GABAA and glycine receptors play critical roles in the organization of fast oscillations into MFO and HFO bands in the phrenic nerve, as well as in their bilateral coupling.
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Bush, E. H., D. R. Spahn, P. F. Niederer, and E. R. Schmid. "Flow Separation, an Important Mechanism in the Formation of Mean Pulmonary Pressure During High-Frequency Oscillation." Journal of Biomechanical Engineering 111, no. 1 (February 1, 1989): 17–23. http://dx.doi.org/10.1115/1.3168333.
Abstract:
Mean pressures within the lungs and lung volume, respectively, are clinically important parameters. During ventilation by way of high-frequency oscillation (HFO), these parameters have been shown to be strongly frequency dependent. To identify mechanisms leading to mean pressure formation during HFO, findings of the theory of stationary flow were extended to oscillatory flow by a quasi-stationary approach. To confirm the theoretical findings, in-vitro experiments on HFO-models were performed. Flow separation was found to be an important mechanism in the formation of mean pressure. Flow separation causes a significant flow resistance, which may be distinctly different for in- and outflow. During oscillatory flow, a mean pressure difference thus results. This mechanism is of particular importance in bifurcations, which are present in the HFO-circuit as well as in the airways. With the direction-dependent flow separation, a general mechanism was found, which accounts for differing mean pressure values within the lungs with different HFO-circuits. This mechanism also contributes to interregionally different mean pressure values within the lungs.
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Ou, Ze, Yu Guo, Payam Gharibani, Ariel Slepyan, Denis Routkevitch, Anastasios Bezerianos, Romergryko G. Geocadin, and Nitish V. Thakor. "Time-Frequency Analysis of Somatosensory Evoked High-Frequency (600 Hz) Oscillations as an Early Indicator of Arousal Recovery after Hypoxic-Ischemic Brain Injury." Brain Sciences 13, no. 1 (December 20, 2022): 2. http://dx.doi.org/10.3390/brainsci13010002.
Abstract:
Cardiac arrest (CA) remains the leading cause of coma, and early arousal recovery indicators are needed to allocate critical care resources properly. High-frequency oscillations (HFOs) of somatosensory evoked potentials (SSEPs) have been shown to indicate responsive wakefulness days following CA. Nonetheless, their potential in the acute recovery phase, where the injury is reversible, has not been tested. We hypothesize that time-frequency (TF) analysis of HFOs can determine arousal recovery in the acute recovery phase. To test our hypothesis, eleven adult male Wistar rats were subjected to asphyxial CA (five with 3-min mild and six with 7-min moderate to severe CA) and SSEPs were recorded for 60 min post-resuscitation. Arousal level was quantified by the neurological deficit scale (NDS) at 4 h. Our results demonstrated that continuous wavelet transform (CWT) of SSEPs localizes HFOs in the TF domain under baseline conditions. The energy dispersed immediately after injury and gradually recovered. We proposed a novel TF-domain measure of HFO: the total power in the normal time-frequency space (NTFS) of HFO. We found that the NTFS power significantly separated the favorable and unfavorable outcome groups. We conclude that the NTFS power of HFOs provides earlier and objective determination of arousal recovery after CA.
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Christakos, C. N., M. I. Cohen, A. L. Sica, W. X. Huang, W. R. See, and R. Barnhardt. "Analysis of recurrent laryngeal inspiratory discharges in relation to fast rhythms." Journal of Neurophysiology 72, no. 3 (September 1, 1994): 1304–16. http://dx.doi.org/10.1152/jn.1994.72.3.1304.
Abstract:
1. Inspiratory (I) activities of recurrent laryngeal (RL) motoneurons and efferent nerves were studied by autospectral, interval, and coherence analyses, with emphasis on fast rhythms of two types: medium-frequency oscillations (MFO, usual range 20-50 Hz for nerve autospectral peaks) and high-frequency oscillations (HFO, usual range 50-100 Hz). 2. In decerebrate, paralyzed, and artificially ventilated cats, recordings were taken from 27 isolated single RL fibers (14 cats) and 8 identified RL motoneurons in the medulla (6 cats), together with recordings of phrenic (PHR) and RL whole-nerve activities. In another 50 cats, RL and PHR nerve discharges were recorded simultaneously. 3. The autospectra of RL units showed prominent MFO peaks with frequencies close to that of the RL nerve MFO spectral peak, indicating presence of this type of fast rhythm in the units' discharges. Spectral analysis of RL unit activity in different segments of the I phase showed that the frequency of a unit's MFO was very close to the peak (maintained) firing rate of the unit during the portion of I analyzed. Thus a motoneuron's MFO spectral peak reflected its rhythmic discharge arising from the cell's refractoriness (and possibly with the rate changing in the course of I). 4. The coherences of motoneurons' MFOs to nerve MFOs were very low or 0, indicating that correlations between unitary MFOs of the RL population were rare and/or weak. 5. In those cats (19/20) that had discernible PHR nerve HFO autospectral peaks, about half of the recorded RL motoneurons (16/34) had HFO. For these motoneurons, the unit-nerve HFO coherences were substantial, indicating widespread correlations between unitary HFOs. 6. In a fraction of cats, coherence peaks in the MFO frequency range were observed between bilateral RL nerves, and between RL and PHR nerves, at frequencies that were subharmonics of the HFO frequency. 7. In light of theoretical considerations on the generation of aggregate rhythms from superposition of unitary rhythms, these observations indicate that, similarly, to the case of PHR motoneurons and nerves. 1) RL nerve MFO arises from superposition of uncorrelated, or at most partially correlated, MFOs of RL units, representing the rhythmic discharges of the cells. It is manifested therefore as a spectral deflection with a maximum in the band of peak firing rates of the units. 2) RL nerve HFO arises from correlated, common-frequency HFOs in a subpopulation of RL units, caused by HFO inputs from antecedent medullary I neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
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Byford, L. J., J. H. Finkler, and A. B. Froese. "Lung volume recruitment during high-frequency oscillation in atelectasis-prone rabbits." Journal of Applied Physiology 64, no. 4 (April 1, 1988): 1607–14. http://dx.doi.org/10.1152/jappl.1988.64.4.1607.
Abstract:
In diffuse lung injury, optimal oxygenation occurs with high-frequency oscillatory ventilation (HFO-A, where A is active expiratory phase) when sustained inflations (SI) are applied periodically to recruit lung volume. Theoretically pulsed pressures may be safer and more effective than static pressures for reexpanding alveoli. We compared the increases in lung volume and arterial PO2 (PaO2) induced by 30-s increases in mean airway pressure in six New Zealand White rabbits made atelectasis prone by saline lavage plus 1 h of conventional ventilation. Pulsatile SI's (HFO-A left on during increase in mean pressure) of delta PSI = 5, 10, and 15 cmH2O and static SI's (HFO-A off during SI) of delta PSI = 5, 10, 15, and 20 cmH2O were delivered in random order. Lungs were ventilated at 15 Hz, inspired fractional concentration of O2 = 1.0, and mean airway pressure 15-20 cmH2O between test periods and deflated to functional residual capacity before each SI to standardize volume history. With both maneuvers, increases in lung volume and PaO2 induced by SI's were proportional to the magnitude of the SI (P less than 0.001) in all cases. Pulsatile SI's consistently increased lung volume and PaO2 more than static SI's having the same delta PSI (P less than 0.005) such that any given target PaO2 or change in volume (delta V) was achieved at 5 cmH2O less mean pressure with the pulsatile maneuver. Respiratory system compliance increased after both types of SI. Oxygenation and lung volume changes at 5 min were related with r = 0.58 (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
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Solimano, A., C. Bryan, A. Jobe, M. Ikegami, and H. Jacobs. "Effects of high-frequency and conventional ventilation on the premature lamb lung." Journal of Applied Physiology 59, no. 5 (November 1, 1985): 1571–77. http://dx.doi.org/10.1152/jappl.1985.59.5.1571.
Abstract:
Twelve sets of twin lambs were delivered prematurely by cesarean section at 133–136 days gestational age and ventilated for 3 h with either high-frequency oscillation (HFO) or conventional mechanical ventilation (CMV). Blood gases and pH values were monitored at 30-min intervals, and ventilator settings were adjusted to maintain CO2 partial pressure (PCO2) values within the normal range. There were no differences in the sequential blood gas or pH values between the HFO or CMV lambs. Mean airway pressures (MAP) between 8.0 and 20.4 cmH2O were required, indicating lung disease of variable severity in the lambs. The bidirectional protein leak from the vascular space to the airways and alveoli and vice versa was measured with radiolabeled albumins given by intravascular injection and with fetal lung fluid at birth. The albumin leaks in both directions increased as MAP required to normalize PCO2 increased, but the degree of leak was independent of type of ventilation. Pathological findings of epithelial necrosis and hyaline membranes occurred to a similar extent in lung sections from both groups of lambs. In the HFO animals less phosphatidylcholine in the alveolar wash and more of a tracer dose of radiolabeled natural surfactant that had been given at birth became tissue associated. These results indicate a decrease in the initial secretion of surfactant and/or a stimulation of reuptake in the HFO animals. HFO did not protect the immature lung from the development of large protein leaks or the pathological changes of the respiratory distress syndrome.