The effect of unilateral tonic muscle activity with and without co-activation of the antagonists on motor cortex excitability has been studied in seven right handed healthy volunteers. Contralateral motor evoked potentials (MEPs) were recorded from the first dorsal interosseous muscles of right hands in response to transcranial magnetic stimulation (TMS) during relax, isometric index finger abduction and antagonistic co-activation. The intracortical facilitation (ICF), short- and long-latency intracortical inhibition (SICI and LICI) were investigated by paired-pulse TMS. The unilateral tonic activation of the right hand facilitated MEPs in response to single-pulse TMS. The increase of MEP amplitudes was significantly greater during isometric index finger abduction compared to co-activation of antagonist muscles. During paired-pulse TMS with short interstimulus intervals, the SICI (interstimulus interval of 3 ms) was not influenced by the unilateral tonic activity while ICF (interstimulus interval of 13 ms) was suppressed. During paired-pulse TMS with longer interstimulus interval (100 ms) the LICI was not influenced during isometric index finger abduction while during antagonistic co-activation the LICI was significantly less pronounced. The decreased LICI is assumed to reflect mechanisms underlying the co-activation of antagonists.

The aim of the present study was to investigate the effect of co-activation of antagonist muscles on long-latency intracortical inhibition (LICI) in comparison to isometric index finger abduction. EMG signals were recorded from the first dorsal interosseous muscle (FDI) in response to single-pulse and paired-pulse transcranial magnetic stimulation (TMS). In 10 healthy right-handed volunteers, TMS was used to estimate LICI at 3 different interstimulus intervals (ISIs) - 50, 100 and 150 ms. The intensity of the conditioning and test stimuli was 130 % of the motor threshold in relax. The stimulation procedure was repeated at rest and during tonic isometric index finger abduction and co-activation of antagonist muscles. At rest, LICI was significant at ISIs of 100 and 150 ms and not evident at ISI of 50 ms. During isometric index finger abduction and co-activation of antagonist muscles, LICI was evident at all used ISIs and was even better pronounced at 50 ms. At ISIs of 50 and 100 ms during abduction, LICI was significantly stronger in comparison to co-activation. During abduction and paired-pulse TMS, the mean values of cSP at all used ISIs were significantly shorter compared to single-pulse TMS. The shortening of cSP recorded in response to paired-pulse TMS was gradual, with increasing of ISI from 50 to 150 ms. In contrast, during co-activation, the duration of cSP was almost independent of the value of ISI and similar to the duration of cSP in response to single-pulse TMS.

The authors' aim was to investigate the changes of corticospinal excitability during kinesthetic illusions induced by tendon vibration. Motor-evoked potentials in response to transcranial magnetic stimulation were recorded from the vibrated flexor carpi radialis and its antagonist, extensor carpi radialis. The illusions were evoked under vision conditions without feedback for the position of the wrist (open or closed eyes). In these two conditions motor-evoked potential changes during vibration in the antagonist were not identical. This discrepancy may be a result of 2 simultaneously acting, different and opposite influences and the balance between them depends on visual conditions. Thus, the illusion was accompanied by the facilitation of corticospinal excitability in both vibrated muscle and its antagonist.

In this work we investigate an image based algorithm as a reliablemethod to perceive the eye movement and offer new possibilities for the activity recognition. In order to test the effectiveness of the algorithm, the eye movement data was recorded using an electrooculography system. Different patterns of eye movement were analyzed within the conducted study. Three different lighting and three activities were performed in order to evaluate the performance of the algorithm.

The interdependences between the maternal heart rate (mHR), the electrohysterogram (EHG) and the fetal heart rate (fHR) are of great interest, indicating the well developing of pregnancy, and they were initially analyzed in the current study by using the spectral coherence. The mHR and fHR were obtained by applying independent component analysis (ICA) and event-synchronous canceller (ESC) algorithms and considered together with the electrohysterogram (EHG) for analysis: their spectra and connectivity were evaluated within the multivariate analysis based on autoregressive model, its parameters being estimated by Kalman filter. The coherence analysis based on Fourier transform, the wavelet coherence and the partial directed coherence were then applied to obtain details about the influences among these signals and the directionality of their interdependences.

Methoden der Informationsfusion sind immer dann erforderlich, wenn Informationen (sensorieller Art oder aus anderen Quellen, z. B. aus Vorwissen) aus mehreren Quellen zusammengeführt (d. h. „fusioniert“) werden sollen.

The acquisition of the fetal electrocardiogram (fECG) signal via abdominal electrodes placed on the maternal abdomen represents an alternative method to the one used currently in clinical practice. It has the advantage that is noninvasive and can be used for long term monitoring of the fetal wellbeing. However, the limit is the low signal to noise ratio (SNR). The abdominal signal (ADS) recorded with the electrodes contains not only the signal of interest, the fECG signal, but also other disturbing signals with a much higher energy than the fECG signal. One of the most disturbing signals is the power line interference (PLI) signal which has a frequency of 50 Hz and usually contains also its harmonics. In this paper different notch filters are implemented and their performance is evaluated on cancelling the PLI signal from the ADS. Because the morphology of the fECG signal represents an important tool of investigating the fetus health status, the influence of the filters on the shape of the signal is stressed out.

Interference of power line (PLI) (fundamental frequency and its harmonics) is usually present in biopotential measurements. Despite all countermeasures, the PLI still corrupts physiological signals, for example, electromyograms (EMG), electroencephalograms (EEG), and electrocardiograms (ECG). When analyzing the fetal ECG (fECG) recorded on the maternal abdomen, the PLI represents a particular strong noise component, being sometimes 10 times greater than the fECG signal, and thus impairing the extraction of any useful information regarding the fetal health state. Many signal processing methods for cancelling the PLI from biopotentials are available in the literature. In this review study, six different principles are analyzed and discussed, and their performance is evaluated on simulated data (three different scenarios), based on five quantitative performance indices.

The fetal electrocardiogram (fECG) obtained from the abdominal signals, to monitor the wellbeing of the fetus, is a weak signal, recorded by placing electrodes on the maternal abdomen surface. When recording the abdominal fECG, the main problem is to separate the fECG from the background noise, including the maternal electrocardiogram (mECG) and/or the power line interference (PLI), this leading to an improved fECG signal to noise ratio (SNR). This paper proposes and evaluates three types of recording configurations, having different reference location, and analyzes the performance of each recording setup, based on the corresponding SNRs, quantitatively evaluated. The fECG extraction is carried out in order to evaluate the performance of each proposed configuration.

Objective: The performance of human operators acting within closed-loop control systems is investigated in a classic tracking task. The dependence of the control error (tracking error) on the parameters display gain, kdisplay, and input signal frequency bandwidth, fg, which alter task difficulty and presumably the control delay, is studied with the aim of functionally specifying it via a model. Background: The human operator as an element of a cascaded human–machine control system (e.g., car driving or piloting an airplane) codetermines the overall system performance. Control performance of humans in continuous tracking has been described in earlier studies. Method: Using a handheld joystick, 10 participants tracked continuous random input signals. The parameters fg and kdisplay were altered between experiments. Results: Increased task difficulty promoted lengthened control delay and, consequently, increased control error. Tracking performance degraded profoundly with target deflection components above 1 Hz, confirming earlier reports. Conclusion: The control error is composed of a delay-induced component, a demand-based component, and a novel component: a human tracking limit. Accordingly, a new model that allows concepts of the observed control error to be split into these three components is suggested. Application: To achieve optimal performance in control systems that include a human operator (e.g., vehicles, remote controlled rovers, crane control), (a) tasks should be kept as simple as possible to achieve shortest control delays, and (b) task components requiring higher-frequency (>1 Hz) tracking actions should be avoided or automated by technical systems.

The analysis of the fetal heart rate (fHR) is important in detecting the fetal distress related with hypoxic episodes, noticed sometimes during the uterine activity, which can severely affect the fetus. Occasional synchrony between the fHR and the maternal heart rate (mHR) was reported and the mHR shows some variations during pregnancy and labor, especially when the contractions are very strong. The current study proposes a new strategy to investigate the relations between the fHR, the mHR and the uterine activity, by applying the time-variant Partial Directed Coherence (tvPDC).

The fetal electrocardiogram (fECG) signal recorded over the maternal abdomen has a weak power mainly due to the small source and the propagation medium formed from different types of tissue layers which have distinct conductivities. This two causes lead to an abdominal recorded fECG with an amplitude of approximate to 10 mu V. Thus, abdominal fECG is very sensitive to noise interference, mainly to the maternal electrocardiogram, mECG and powerline interference (PLI). The study presents new possibilities in obtaining reliable fECG signal, i.e. with diagnostic capabilities, from abdominal recordings. Four different concepts are defined and analyzed and the concentric ring electrodes for recording fECG are introduced.

Fetal ECG (fECG) signal offers valuable information about the health state of the fetus during pregnancy that can assist physicians taking timely the appropriate decisions during pregnancy and labor. Thus, the FECG signal extraction from composite abdominal signals (ADS) by powerful and advance signal processing methods is becoming more and more an important requirement for fetal monitoring. This paper presents the evaluation of four Independent Component Analysis (ICA) algorithms, when used for fECG extraction, and their performance comparison when considering the application of the Event Synchronous Canceller (ESC) as a preprocessing step that cancel the maternal ECG (mECG). The algorithms are evaluated when considering two data sets of simulated ADS.

The abdominal signal recorded on the abdomen of a pregnant woman allows the fECG extraction for a further analysis. The main problem when using the ADSs is that they contain not only the signals of interest but also some disturbing signals that influence the fECG extraction methods. This study proposes an adaptive algorithm that removes the main PLI frequency and its harmonics from the real and simulated abdominal signals. The algorithm is quite stable and preserve the fECG morphology.

Nowadays, one the most prevalent arrhythmia is the atrial fibrillation (AF). The affection associated with AF can lead from problems like hypertension, to life threatening problems such as thromboembolic events. It can be identified using a routine electrocardiogram (ECG) investigation and is characterized by the chaotic-like oscillations, f-waves, which replace the P wave. In the present paper the evaluation of a previously proposed method is performed on simulated data sets which include noise components with different signal to noise ratios (SNR).

Current medical research aims to continuously improve diagnostic tools, and thus to develop new assessment methods, less invasive and when long-term monitoring is the case, as in telemonitoring systems less annoying for the patient. Many improvements of clinical investigations are directed by cost reduction; therefore, upgrading existing inexpensive techniques such as the direct recording of biosignals from the body surface is of utmost interest (Groves, 2008). Currently, research and development are mainly focused on offering reliable medical devices and techniques for disabled and elderly people (Alemdar et al., 2010; Feng et al. 2010; Tay, 2009; Mestre, 2005; Corchado, 2010; Fleury, 2010). Concomitantly, there are ethical and social aspects that make medical care also focus on the first years of life, including the prenatal period, since disorders and handicaps acquired during this time will be long lasting and an extreme load for the subject, for the family, and for the society, as well. Since these individuals are not autonomous, but totally dependent on the adults, the society is also responsible for their health for obvious ethical reasons. Therefore, prenatal health care is an important topic in biomedical research, and fetal monitoring is one of its most important components (Di Lieto et al., 2008; Ippolito et al., 2003; Kosa et al., 2008; Hod and Kerner, 2003; Dalfra, 2009; Kerner, 2004; Di Lieto, 2002). Fetal electrocardiogram (fECG) and electroencephalogram (fEEG) can be used to investigate the general wellbeing and the brain development. The current clinical methods are mainly based on the fetal heart rate variability (fHRV) analysis (Kovacs et al., 2000; Varady et al., 2003; Horvath et al., 2007). Currently, the noninvasive cardiotocographic technique is the standard clinical approach because its use is possible during both pregnancy and labor. Alternatively, the fetal Doppler ultrasound is used during pregnancy, but not during labor (1) because of its sensitivity to the movement either of the mother or of the fetus, and (2) because of the errors induced by the uterine activity. Furthermore, the side effect of long-term ultrasonic exposure on the fetus and young infants is not completely clear, and that is why this method is not recommended for

Atrial fibrillation (AF) is the most prevalent arrhythmia with which the physicians are confronted nowadays. This type of affection can lead from problems like hypertension, to life threatening problems such as thromboembolic events. It can be identified using a routine electrocardiogram (ECG) investigation and is characterized by the chaotic-like oscillations, f-waves, which replace the P wave. In the present paper a combination of two conceptually different methods is presented: the Event Synchronous Canceller, ESC, for the cancellation of the QRS-T and Independent Component Analysis, ICA, for the extraction of the AF signal. The proposed algorithm is applied successfully on both realistic simulated ECG with AF signals and on a database of real signals, St.-Petersburg Institute of Cardiological Technics 12-lead Arrhythmia Database from the MIT database Physionet.

The effect of subthreshold transcranial magnetic stimulation (TMS) on simple reaction time (RT) was examined. Subjects responded with isometric index finger abduction with and without TMS application. Motor evoked potentials and myoelectrical activity were recorded from the right first dorsal interosseous muscle. Single pulses TMS of four different subthreshold intensities were delivered to the left motor cortex at variable delays after visual Go-Signal. Regardless of the TMS intensity, RT depends significantly on the TMS delay. At shorter delays RT was shorter and at longer delays RT was longer. An "empty" interval was recognized in trials with intensities higher than 60% of motor threshold at rest. Two processes operate in premovement period: inhibitory effect of TMS tending to delay motor reaction and premovement facilitation starting 100 ms before response onset tending to accelerate the motor reaction. The impact effect of both mechanisms is a gradual shortening of RT.

Fetal monitoring using abdominally recorded signals (ADS) allows physicians to detect occurring changes in the well-being state of the fetus from the beginning of pregnancy. Mainly based on the fetal electrocardiogram (fECG), it provides the long-term fetal heart rate (fHR) and assessment of the fetal QRS morphology. But the fECG component in ADS is obscured by the maternal ECG (mECG), thus removal of the mECG from ADS improves fECG analysis. This study demonstrates the performance of the event-synchronous interference canceller (ESC) in mECG removal from ADS data, recorded during pregnancy and labor. Its advantage as a compensation method for extended ADS processing is discussed.