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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The evaluation of EEG-findings during the acute phase of stroke-patients is somewhat difficult particularly in regard to the voltage-production, less in regard to the temporary retardation of frequency. Within comparable neurophysiological and biochemical examinations of the experimental brain-infarct under standardized conditions of silicon-rubber-embolus was introduced intracarotideally and an occlusion of the media-trunk evoked. One day prior to the embolisation and on the first, third and fifth day thereafter EEG-derivation took place which were stored on analogous-tape, digitalized and were then confronted with the FFT-Algorithm. From the statistical point of view four animal groups were the result: HO-group (control group), H1-, H3- and H5-group (each time N = 6). Visual evaluation of the curves, descriptive and inferential statistics of the spectral EEG estimators showed a significant loss of power within five days after the infarction; it always was more distinct across the focal side than across the not immediately involved hemisphere. On the fifth day the original level of voltage was almost reached again. From the clinical standpoint the neurological deficits had practically been disappeared. The biochemical finishing of the dog-brains -- the results of which are planned to be confronted with the electrophysiological results in another paper -- in accordance with the papers of other authors brings close the assumption that the decrease of tension i.e. the loss of power of the electric potential during the first days after infarction is combined with a temporary decrease of the energetic potential of the metabolically active corticocerebral cells which is tied to the phosphagene-system of the highly energetical phosphates and metabolites of the energy-metabolism in the brain.
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PMID:[Electroencephalographic study of brain-infarction in dogs (author's transl)]. 82 64

A new 1MHz continuous wave Doppler device with adaptive digital data processing was introduced to fetal heart rate monitoring during labor. Frequency characteristics of three different continuous wave Doppler devices (2MHz, 1MHz, and 455kHz) were evaluated by FFT analysis, after triggering at the QRS peaks of simultaneously recorded fetal scalp ECG. By three dimensional FFT display, the 1MHz carrier frequency was found to be optimal because of its improved penetration and coverage of a wider area, than with 2MHz and 455kHz. It was obvious that the 1MHz signal provided simplified wave form patterns, and this was much more convenient in detecting the individual valve or flow signal originating in the fetal heart. However, the study revealed that at 455kHz, which was theoretically a compatible figure considering the size and the stroke of the fetal heart, the nature of Doppler signal was different from those at a higher frequency, suggesting that it is inconvenient for exact determination of the fetal heart rate. Another point to emphasize is the application of an adaptive equalizer. This equalizer gave a constant configuration of the Doppler signal, by calculating the average output level in the amplitude and frequency range during a given time interval. By this newly-devised specific filtering, the individual valve or flow component could be easily discerned. This analysis showed that the combination of a 1MHz Doppler device and an adaptive equalizer to be the best device for fetal heart rate monitoring during labor.
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PMID:[The 1MHz C-W Doppler device with an adaptive equalizer for fetal heat rate monitoring during labor]. 354 40

Atrial fibrillation (AF), which is rather a common disease has a high risk of developing systemic embolism and stroke. Accordingly it can be significant for us to predict a patient at risk for AF during sinus rhythm Recently signal averaged ECG triggered by P wave has been expected to detect atrial late potential (ALP), which is thought to coincide with fractionated ECG significantly recorded directly from atrial muscle of a patient with paroxysmal AF. Although many time-domain ALP indices have been proposed, those excepting filtered P duration remain controversial with their diagnostic criteria having not yet been established, many studies agree as to the prolongation of filtered P duration, as observed for patients with AF. Although, also recently, frequency domain method has been applied to ALP for FFT analysis with the view of detecting ALP possibly undetectable by time domain method, no results better than the above method have been obtained, and further examination is hoped for.
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PMID:[Atrial late potential by P wave-triggered signal-averaged electrocardiogram and paroxysmal atrial fibrillation]. 769 78

The objective of our study was to compare the cardiovascular effects of moderate exercise training in healthy young (NTS, n=18, 22.9+/-0.44 years) and in hypertensive human subjects (HTS, n=30, 23+/-1.1). The VO(2max) did not significantly differ between groups. HTS of systolic blood pressure (SBP) 148+/-3.6 mmHg and diastolic blood pressure(DBP) 88+/-2.2 mmHg, and NTS of SBP: 128.8 +/- 4 mmHg and DBP: 72 +/- 2.9 mmHg were submitted to moderate dynamic exercise training, at about 50% VO(2max) 3 times per week for one hour, over 3 months. VO(2max) was measured by Astrand's test. Arterial blood pressure was measured with Finapres technique, the stroke volume, cardiac output and arm blood flow were assessed by impedance reography. Variability of SBP and pulse interval values (PI) were estimated by computing the variance and power spectra according to FFT algorithm. After training period significant improvements in VO(2max) were observed in NTS- by 1.92 +/-0.76 and in HTS by 3+/-0.68 ml/kg/min). In HTS significantly decreased: SBP by 19 +/-2.9 mmHg, in DBP by 10.7+/-2 mmHg total peripheral resistance (TPR) by 0.28 +/-0.05 TPR units. The pretraining value of low frequency component power spectra SBP (LF(SPB)) was significantly greater in HTS, compared to NTS. PI variance was lower in HTS, compared to NTS. After physical training, in HTS PI variance increased suggesting a decrease in frequency modulated sympathetic activity and increase in vagal modulation of heart rate in mild hypertension. A major finding of the study is the significant decrease of resting low frequency component SBP power spectrum after training in HTS. The value of LF(SPB) in trained hypertensive subjects normalized to the resting level of LF(SPB) in NTS. Our findings suggest that antihypertensive hemodynamic effects of moderate dynamic physical training are associated with readjustment of the autonomic cardiovascular control system.
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PMID:Effects of moderate physical training on blood pressure variability and hemodynamic pattern in mildly hypertensive subjects. 1561 38

Atrial fibrillation (AF) is a common arrhythmia characterized by irregular ventricular response. During AF, beat-to-beat variability of arterial pressure (AP) is increased because of continuous changes in filling time, stroke volume and contractility. Only a few studies have analyzed short-term AP variability during AF but they were mainly focused on the effects of respiration. We therefore analyzed short-term systolic (S), diastolic (D) and mean (M) AP variability by autoregressive method and an FFT-based spectral estimation (Welch periodogram) in 26 patients with persistent AF before and after restoration of sinus rhythm by electrical cardioversion. A low frequency (LF) component (central frequency 0.07+/-0.02 Hz, mean+/-standard deviation) of SAP variability was observed in 23 out of 26 patients during AF. Frequency analysis of DAP and MAP also showed a LF component with a central frequency of 0.08+/-0.03 Hz (20 patients) and 0.07+/-0.03 Hz (25 patients), respectively. After recovery of sinus rhythm, we found significant reduction in mean SAP, DAP and MAP variability in all frequency bands. Squared coherence between SAP and heart rate variability after recovery of sinus rhythm revealed a weak and strong coupling within, respectively, LF and HF frequency bands. These data indicate that in patients with AF, in spite of an absence of rhythmical oscillation in RR interval time series, it is possible to observe a LF component in SAP, DAP and MAP variability signals. These 0.1 Hz fluctuations reflect the influence of the sympathetic fibres acting on the cardiovascular system.
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PMID:Low frequency component in systolic arterial pressure variability in patients with persistent atrial fibrillation. 1959 12

While the peri-infarct cortex is thought to be responsible for functional recovery, the site is also a strong candidate for post-stroke seizures. Since it is crucial to identify the conditions when the site is changed with such beneficial or detrimental results, the peri-infarct changes were investigated before and just after inducing a focal infarct on rat cortex. The receptive fields in the peri-infarct cortex began to increase a few hours after the infarct, and reached a statistical significance at 6 hours (Dunnett post hoc tests; p<0.05). In temporal association with these changes, EEG in the peri-infarct cortex showed epileptiform activities containing large-amplitude spike-and-wave discharges. The gross amplitude, peak-to-peak amplitude and burst frequency showed statistically significant increases within 4 hours, in comparison to those of the controls (Dunnett post hoc tests; p<0.05). FFT power spectrum analyses showed a distinct increase in approximately 25 Hz frequency bands in the post-stroke groups. The homogeneous area of the contralateral hemisphere in the infarct group, in contrast, did not show such plastic or excitability changes. This study demonstrated, for the first time, that the peri-infarct cortex acquires the characteristics of potential epileptogenesis and functional recovery within hours of a stroke.
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PMID:Epileptiform discharges and neuronal plasticity in the acute peri-infarct cortex of rats. 1968 9

Tremor, defined as a rhythmic and involuntary oscillation of a body part, is considered one of the most common disturbances of movement. The most frequent pathological forms, mainly affecting elderly people, are the essential tremor, the Parkinson's disease tremor and the physiological tremor. In order to examine the characteristics of a tremor, methods based on accelerometry and electromyography measures and more recently spirometry test, based on a digital acquisition of hand movements drawing an Archimedes' spiral, have been used. Though the quantification of tremors is the object of study for several researchers, today a standard method does not exist yet [1]. The most common techniques examine the frequency of tremors, however there is no consensus in literature on its value among the various pathological forms. As for handwriting, characteristics of tremors can be investigated from a kinematic point of view. For this aim, in this paper new quantitative kinematic parameters are proposed and their potential is evaluated on three groups of subjects (two with pathological tremors and a control group). Each subject underwent a set of four graphical tests (Horizontal Rows, Archimedes' Spiral, Triangle and Square) and the kinematic parameters calculated on the recordings were examined in order to establish which test and parameters are more sensitive to tremor differences and appropriate for pathologies identification. Significant differences were found for the number of strokes (being the stroke the base element of each hand movement), the number of ascending / descending tracts, the zero-crossing of velocity and acceleration profiles, the line curvature, the angular velocity and the dominant frequencies values extracted from FFT analysis of velocities, especially in relation with the Rows and Spiral tests. Depending on the test, some other significant differences were found in the velocity and acceleration mean values as well as in the number of components and pen-lift intervals. The results support the hypothesis that kinematic analysis can be useful in tremor studies and when used with suitable tests it can differentiate among pathological and normal subjects.
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PMID:Kinematic analysis of tremor - biomed 2010. 2046 7

A key issue in brain-computer interface (BCI) is the detection of intentional control (IC) states and non-intentional control (NC) states in an asynchronous manner. Furthermore, for steady-state visual evoked potential (SSVEP) BCI systems, multiple states (sub-states) exist within the IC state. Existing recognition methods rely on a threshold technique, which is difficult to realize high accuracy, i.e., simultaneously high true positive rate and low false positive rate. To address this issue, we proposed a novel convolutional neural network (CNN) to detect IC and NC states in a SSVEP-BCI system for the first time. Specifically, the steady-state motion visual evoked potentials (SSMVEP) paradigm, which has been shown to induce less visual discomfort, was chosen as the experimental paradigm. Two processing pipelines were proposed for the detection of IC and NC states. The first one was using CNN as a multi-class classifier to discriminate between all the states in IC and NC state (FFT-CNN). The second one was using CNN to discriminate between IC and NC states, and using canonical correlation analysis (CCA) to perform classification tasks within the IC (FFT-CNN-CCA). We demonstrated that both pipelines achieved a significant increase in accuracy for low-performance healthy participants when traditional algorithms such as CCA threshold were used. Furthermore, the FFT-CNN-CCA pipeline achieved better performance than the FFT-CNN pipeline based on the stroke patients' data. In summary, we showed that CNN can be used for robust detection in an asynchronous SSMVEP-BCI with great potential for out-of-lab BCI applications.
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PMID:A Convolutional Neural Network for the Detection of Asynchronous Steady State Motion Visual Evoked Potential. 3107 Oct 44