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Hz Oscillation (hz + oscillation)

Distribution by Scientific Domains
Medical Sciences50%

Selected Abstracts

Low-level defective processing of non-verbal sounds in dyslexic children

DYSLEXIA, Issue 2 2009
Paulino Uclés
Abstract We compared processing of non-verbal auditory stimuli by dyslexic and non-dyslexic children using electrophysiological methods. The study included 39 children (17 with dyslexia plus 22 controls) assessed via frontal, central, parietal, and temporal electrodes. As an extension of previous P300 event-related potential studies, we analysed variations in the power values of 40-Hz oscillations (gamma-band oscillations involved in cognitive processing) during a specific time window in response to the auditory ,oddball' paradigm that entail target (random 2,kHz) and standard (frequent 1,kHz) stimuli. Dyslexic children differed significantly from controls (P<0.001) in the mean power of the wavelet-transformed 40-Hz oscillation in a time interval starting at 25 ms after stimulus onset up to 50 ms. This means defective processing of sounds. Within groups, standard and target tones elicited significantly different power values (P<0.001). Correlations of values between standard and target responses at each electrode position were not significant within either group, although dyslexics showed a lower correlation than controls. Significant differences in the mean power of these oscillations detected at very early stages of auditory processing in dyslexic children and the wide range of mean values reveal impairment in processing non-verbal sounds in dyslexia. Our results also support recent findings using behavioural and electrophysiological methods suggesting that dyslexia is a general auditory deficit instead of a speech-specific deficit. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Impaired cardiovagal and vasomotor responses to baroreceptor stimulation in type II diabetes mellitus

EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 7 2003
E. O. Sanya
Abstract Background In diabetic patients, impairment of the cardiovagal limb of the baroreflex has been well established. However, the role of sympathetic mediated baroreflex vasomotor control of the blood vessels is not well defined. We therefore assessed the vasomotor responses to sinusoidal baroreceptor stimulation in diabetic patients. Materials and methods We studied 14 type II diabetic patients (age; 57 ± 7 years) and 18 healthy controls (age; 59 ± 11 years). Oscillatory neck suction was applied at 0·1 Hz to assess the sympathetic modulation of the heart and blood vessels, and at 0·2 Hz to assess the effect of parasympathetic stimulation on the heart. Breathing was paced at 0·25 Hz. Spectral analysis was used to evaluate the oscillatory responses of RR-interval and blood pressure. Results The diabetic patients showed a significantly lower RR-interval response (P < 0·05) to the 0·1 Hz neck suction (2·52 ± 0·50,3·62 ± 0·54 ln ms2) than the controls (4·23 ± 0·31,6·74 ± 0·36 ln ms2). The increase in power of 0·1 Hz systolic blood pressure oscillations during 0·1 Hz suction was also significantly smaller (P < 0·05) in the diabetics (1·17 ± 0·44,1·69 ± 0·44 mmHg2) than in the controls (1·60 ± 0·29 mmHg2,5·87 ± 1·25 mmHg2). The magnitude of the peak of the 0·2 Hz oscillation in the RR-interval in response to 0·2 Hz neck stimulation was significantly greater (P < 0·05) in the controls (3·42 ± 0·46 ln ms2) than in the diabetics (1·58 ± 0·44 ln ms2). Conclusion In addition to cardiovagal dysfunction, baroreflex-mediated sympathetic modulation of the blood vessels is impaired in type II diabetic patients. [source]

Safety aspects for public access defibrillation using automated external defibrillators near high-voltage power lines

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 5 2004
C. J. Schlimp
Background:, Automated external defibrillators (AEDs) must combine easy operability and high-quality diagnosis even under unfavorable conditions. This study determined the influence of electromagnetic interference caused by high-voltage power lines with 16.7-Hz alternating current on the quality of AEDs' rhythm analysis. Methods:, Two AEDs frequently used in Austria were tested near high-voltage power lines (15 kV or 110 kV, alternating current with 16.7 Hz). The defibrillation electrodes were attached either to a proband with true sinus rhythm or to a resuscitation dummy with generated sinus rhythm, ventricular fibrillation, ventricular tachycardia or asystole. Results:, Electromagnetic interference was much more prominent in a human's than in a dummy's electrocardiogram and depended on the position of the electrodes and cables in relation to the power line. Near high-voltage power lines the AEDs showed a significant operational fault. One AED interpreted the interference as a motion artifact, even when underlying rhythms were clearly detectable. The other AED interpreted 16.7-Hz oscillation as ventricular fibrillation with consequent shock advice when no underlying rhythm was detected. Conclusion:, The tested AEDs neither filter nor recognize a technical interference of 16.7 Hz caused by 15-kV power lines above railway tracks or 110-kV overland power lines, as run by railway companies in Austria, Germany, Norway, Sweden and Switzerland. These failures in AEDs' algorithms for rhythm analysis may cause substantial harm to patients undergoing public access defibrillation. The proper function of AEDs needs to be reconsidered to guarantee patients' safety near high-voltage power lines. [source]

Low-level defective processing of non-verbal sounds in dyslexic children

DYSLEXIA, Issue 2 2009
Paulino Uclés
Abstract We compared processing of non-verbal auditory stimuli by dyslexic and non-dyslexic children using electrophysiological methods. The study included 39 children (17 with dyslexia plus 22 controls) assessed via frontal, central, parietal, and temporal electrodes. As an extension of previous P300 event-related potential studies, we analysed variations in the power values of 40-Hz oscillations (gamma-band oscillations involved in cognitive processing) during a specific time window in response to the auditory ,oddball' paradigm that entail target (random 2,kHz) and standard (frequent 1,kHz) stimuli. Dyslexic children differed significantly from controls (P<0.001) in the mean power of the wavelet-transformed 40-Hz oscillation in a time interval starting at 25 ms after stimulus onset up to 50 ms. This means defective processing of sounds. Within groups, standard and target tones elicited significantly different power values (P<0.001). Correlations of values between standard and target responses at each electrode position were not significant within either group, although dyslexics showed a lower correlation than controls. Significant differences in the mean power of these oscillations detected at very early stages of auditory processing in dyslexic children and the wide range of mean values reveal impairment in processing non-verbal sounds in dyslexia. Our results also support recent findings using behavioural and electrophysiological methods suggesting that dyslexia is a general auditory deficit instead of a speech-specific deficit. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Area-Specific Resonance of Excitatory Networks in Neocortex: Control by Outward Currents

EPILEPSIA, Issue 8 2007
Manuel A. Castro-Alamancos
Summary:, During disinhibition or low [Mg++]o buffer, 7,14 Hz (,10 Hz) oscillations are generated by excitatory networks of interconnected pyramidal cells in motor (agranular) cortex but are absent in barrel (granular) cortex. Here we studied if the inability of barrel cortex to produce ,10 Hz oscillations during these conditions is because barrel cortex networks lack the necessary cellular mechanisms or, alternatively, because those mechanisms are inhibited by outward currents. The results show that blockers of slowly inactivating voltage-dependent K+ currents unmask ,10 Hz oscillations in barrel cortex, and this occurs in unison with the unmasking of intrinsic inward Ca++ currents that are kept suppressed by the outward currents. Moreover, the ,10 Hz oscillations unmasked in barrel cortex occur independently in upper and lower layers indicating that the ,10 Hz oscillation mechanisms are kept suppressed in multiple networks. The results reveal that the propensity of distinct excitatory networks of neocortex to generate epileptiform oscillatory activities is controlled by outward currents. [source]

Theoretical evaluation of magnetoreception of power-frequency fields

BIOELECTROMAGNETICS, Issue 5 2010
Jacques Vanderstraeten
Abstract Several effects of power-frequency (50/60,Hz) magnetic fields (PF-MF) of weak intensity have been hypothesized in animals and humans. No valid mechanism, however, has been proposed for an interaction between PF-MF and biological tissues and living beings at intensities relevant to animal and human exposure. Here we proposed to consider PF-MF as disrupters of the natural magnetic signal. Under exposure to these fields, an oscillating field exists that results from the vectorial summation of both the PF-MF and the geomagnetic field. At a PF-MF intensity (rms) of 0.5,µT, the peak-to-peak amplitude of the axis and/or intensity variations of this resulting field exceeds the related discrimination threshold of magnetoreception (MR) in migrating animals. From our evaluation of the 50/60,Hz responsiveness of the putative mechanisms of MR, single domain particles (Kirschvink's model) appear unable to transduce that oscillating signal. On the contrary, radical pair reactions are able to, as well as interacting multidomain iron,mineral platelets and clusters of superparamagnetic particles (Fleissner/Solov'yov's model). It is, however, not yet known whether the reception of 50/60,Hz oscillations of the natural magnetic signal might be of consequence or not. Bioelectromagnetics 31:371,379, 2010. © 2010 Wiley-Liss, Inc. [source]