Investigation and comparison of some models for removing ocular artefacts from EEG signals

An investigation of ocular artefacts (OAs) in the human electroencephalogram (EEG) to quantify the effectiveness of OA removal, and to find the most effective model for removing OAs online is described. It was found unnecessary to use the vertical and horizontal EOGs of both eyes, although more than one EOG signal is required for adequate OA removal. The model using the vertical right EOG and the two horizontal EOGs was the best overall, but in most cases the use of only the vertical and horizontal right EOGs was sufficient. OAs were not completely removed by any of the models investigated, suggesting that more complex models are necessary.     

Non-invasive estimation of myocardial infarction by means of a heart-model-based imaging approach: A simulation study

In the study, a new myocardial infarction (MI) estimation method was developed for estimating Ml in the three-dimensional myocardium by means of a heart-model-based inverse approach. The site and size of Ml are estimated from body surface electrocardiograms by minimising multiple objective functions of the measured body surface potential maps (BSPMs) and the heart-model-generated BSPMs. Computer simulations were conducted to evaluate the performance of the developed method, using a single-site Ml and dual-site Ml protocols. The simulation results show that, for the single-site Ml, the averaged spatial distance (SD) between the weighting centres of the ‘true’ and estimated Mls, and the averaged relative error (RE) between the numbers of the ‘true’ and estimated infarcted units are 3.0±0.6/3.6±0.6 mm and 0.11±0.02/0.14±0.02, respectively, when 5μV/10μV Gaussian white noise was added to the body surface potentials. For the dual-site Ml, the averaged SD between the weighting centres of the ‘true’ and estimated Mls, and the averaged RE between the numbers of the ‘trus’ and estimated infarcted units are 3.8±0.7/3.9±0.7 mm and 0.12±0.02/0.14±0.03, respectively, when 5μV/10μV Gaussian white noise was added to the body surface potentials. The simulation results suggest the feasibility of applying the heart-model-based imaging approach to the estimation of myocardial infarction from body surface potentials.     

Influence of diet on metastasis and tumor dormancy

Tumor metastasis is responsible for most cancer deaths, and can occur after long periods of tumor dormancy. Information learned from experimental studies on tumor metastasis and dormancy is shedding light on mechanisms responsible and possible therapeutic approaches. ‘Seed’ (the cancer cell) and ‘soil’ (the microenvironment of the secondary organ) factors contribute to metastatic outcome. This review considers the possibility that various dietary components may affect both ‘seed’ and ‘soil’ compartments, thereby influencing the growth of metastases, and discusses an experimental study on dietary genistein that illustrates this concept. While studies on human diet are complex, the possibility that relatively non-toxic dietary intervention strategies could impact on metastasis and patient survival is attractive and worthy of further study in appropriate experimental models of metastasis and tumor dormancy.     

The removal of ocular artefacts from the electroencephalogram: a review

The causes of ocular artefacts (OAs) in the human electroencephalogram (EEG) are explained and methods for their removal and their effectiveness are discussed. Recommendations for the best procedures to adopt are given together with suggestions for future research. Analogue subtraction techniques are found to be inferior to time domain techniques based on parameter estimation using the method of least squares applied to a linear function of the electro-occulograms (EOGs). Ways of assessing the effectiveness of different models for time domain removal of OAs are discussed. It is concluded that autoregressive modelling of the error terms, or else differenced data, must be used to reduce the effects of correlation in the background EEG. The most generally suitable model for the removal of random eye and blink artefacts should contain terms proportional to the right vertical EOG and the two horizontal EOGs. The EOGs should be linearly filtered to remove noise frequency components in excess of 8 Hz. Adaptive methods are preferred as on line OA removal would be desirable but for the fact that this may result in distortion of stimulus-related responses present. A number of difficulties remain and there are some suggestions for future research.     

Spectra of data sampled at frequency-modulated rates in application to cardiovascular signals: Part 2 evaluation of Fourier transform algorithms

For three direct Fourier transform algorithms we quantified the influence of pulse frequency modulation (PFM) on the spectral estimation of pulse amplitude modulation (PAM). The simulation study is based on sinusoid functions sampled according to a pulse sequence which is the output of an integral pulse frequency modulator (IPFM). One algorithm exactly reproduces the theoretical spectrum derived in Part 1. The other two, including the classical FFT, scale all PFM-induced components in a different way, and in addition, generate higher modulating frequency harmonics. For a PFM depth below 30%, the sum of spurious PFM components is almost linearly dependent on this modulation depth, for all three algorithms. Dividing the effect of PFM in a ‘harmonic’ and ‘aliasing’ distortion, we found that the FFT has a relatively high harmonic distortion, compared to an algorithm that takes into account the non-uniform character of the data. In the cardiovascular (worst) case of 30% modulation in heart rate (PFM) at a frequency of 0.1 Hz, the FFT spectrum of beat-to-beat systolic blood pressure variations contains approximately 20% of spurious components caused solely by the modulation in time occurrences of the blood pressure samples. The ‘non-uniform’ algorithm performs twice as well in this case.     

Pre-screening via sleep logs in sleep-disordered patients—Adaptational effects, yes or no?

Summary Question of the study  Sleep logs are common tools in sleep research and clinical routine. Usually sleep logs have to be completed during a 2-week period, with the first week serving as an adaptation to the instrument itself. In the present study, we investigated whether there is indeed such an adaptation bias or not. Patients and methods  A total of 236 chronically sleep-disordered outpatients completed the standardized sleep log ‘Abend-Morgen-Protokoll’ during a 2-week pre-screening period prior to the first visit in our sleep ambulance. Two sets of items were established, the ‘instrumental’ and the ‘therapeutic’ set. The respective ratings of the first and second week (week A, B) were compared to evaluate clinically relevant changes. Results  The ratings of several ‘instrumental’ items significantly differed between week A and B. However, these changes—on average—were only marginal and therefore of little clinical importance. Regarding the ‘therapeutic’ set of items, no systematic variations could be ascertained over the assessment period. Conclusion  The present investigation could not confirm the presence of adaptation biases (instrumental, therapeutic) in a large sample of chronically sleep-disordered outpatients. Therefore, we consider a 1-week pre-screening period via sleep log as sufficient for the diagnostic process in these patients.      

Detection of alpha electro-encephalogram onset following eye closure using four location-based techniques

Detection of alpha activity in the electro-encephalogram (EEG) has been used extensively in neurophysiological studies. Previously applied alpha parameterisation techniques, which utilise the amplitude information from a pair of differential electrodes, are often susceptible to interference from artifact signals. This is an issue if the purpose of detecting the change in alpha wave synchronisation is the basis of an environmental control system (ECS). An alternative approach to alpha activity detection is proposed that utilises the information from an array of electrodes on the scalp to estimate the apparent location of alpha activity in the brain. Four methods are described that successfully detect the onset of alpha EEG increase following eye closure by monitoring the apparent location of alpha activity in the head. The methods use Bartlett beamforming, a four-sphere anatomical head model, the MUSIC algorithm and a new ‘power vector’ technique. Of the methods described, the power vector technique is found to be the most successful. The power vector technique detects the alpha increase associated with eye closure in times that are, on average, 33% lower than previously applied alpha detection methods.     

Variability in use of cut-off scores and formats on the Edinburgh Postnatal Depression Scale – implications for clinical and research practice

Summary Objectives: i) To highlight the increasing use in the literature of unvalidated cut-off scores on the Edinburgh Depression Scale (EDS/EPDS), as well as different wording and formatting in the scale; ii) to investigate and discuss the possible impact of using an unvalidated cut-off score; iii) to highlight possible reasons for these ‘errors’; and iv) to make recommendations to clinicians and researchers who use the EDS/EPDS. Method: A convenience sample of studies that have used unvalidated cut-off scores, or different formatting, are cited as evidence that these types of ‘errors’ are occurring fairly frequently. Examination of previous data from one of the authors is undertaken to determine the effect of using an unvalidated cut-off score. Summary: Many studies report rates of high scorers on the EDS/EPDS using different cut-off scores to the validated ones. The effect of doing this on the overall rate can be substantial. The effect of using different formatting is not known, though excluding items from the EDS/EPDS must also make a substantial difference. Recommendations: We recommend that i) the validated score of 13 or more is used when reporting on probable major depression in postnatal English-speaking women, and 15 or more when reporting on antenatal English-speaking women; ii) that the wording used is “13 or more” (or equivalent), and not other terms that may cause confusion (e.g., ‘>12’; ‘more than 12’; ‘13’ etc), iii) if a different cut-off score to the validated one is used, a clear explanation is given as to why this has been done; and iv) that the scale should be worded and formatted as originally described by its authors.     

Finger interaction during maximal radial and ulnar deviation efforts: experimental data and linear neural network modeling

The purpose of this study was to characterize finger interactions during radial/ulnar deviation, including interactions with flexion movements. Subjects performed single-finger and multi-finger maximal voluntary contraction (MVC), and maximal forces and various indices of interaction among the fingers were quantified. MVCs in radial/ulnar deviation were 50–80% as strong as in flexion. Along with the ‘master’ fingers (i.e., those explicitly instructed to produce force), substantial force production was also observed in ‘slave’ fingers (i.e., those not explicitly instructed to produce force), a phenomenon termed: force ‘enslaving’. In addition, a drop in MVC during multi-finger tasks as compared to single finger tasks (force ‘deficit’) was also observed. A previously unreported phenomenon that we term: ‘preferred direction enslaving’ was also apparent; both master and slave fingers produced force in the instructed direction with a non-zero perpendicular component. Due to the architectural separation of the involved muscles, preferred direction enslaving provides strong evidence that enslaving results from neural rather than biomechanical factors. A final new phenomenon: ‘negative deficit’, or force ‘facilitation’ was observed in 46.4% of the trials in 21 out of 23 subjects during multi-finger lateral efforts and was further demonstrative of extensive interconnection among neurons serving hand muscles. The data were modeled with high accuracy (∼4% mean square error) using a linear neural network with motor ‘commands’ as inputs and finger forces as outputs. The proposed network, equivalent to linear regression, can be used to determine the extent to which finger forces are influenced by peripheral constraints during functional prehensile activities.     

Fractal dynamics of polarized bioelectrodes

This study is concerned with mathematical modelling of the fundamental relationship which exists between the current density and the overpotential across the metalsolution interface in the linear range using methods of system theory enhanced by ‘fractal’ concepts. A primer for both 1/f-type scaling and ‘anomalous’ relaxation/dispersion concepts is provided, followed by a brief review of the research history pertinent to the metal electrode polarization dynamics. Next, the ‘fractal relaxation systems’ approach is introduced to characterize, systems which attenuate with a fractional power-low dependence on frequency through a ‘scaling exponent’. The ‘singularity structure’ which is a scaling, rational system function is proposed to expand fractal systems in terms of basic subsystems individually representing elementary exponential relaxations and collectively exhibiting scaling properties. We stress that the ‘singularity structure’ carries scaling information identical to the conventional ‘distribution of relaxation times’ function. ‘Structure scale’ and ‘view scale’ concepts are presented in the due course to streamline the analysis of scaling phenomena in general and the polarization impedance in particular. System theory-wise, the notable result is that the fractional power function attenuation, or equivalently, the logarithmic nature of the distribution function translates into the ‘self-similar’ pattern replication of the system singularities in the s-plane. The singularity arrangement is governed by a recursive rule solely based on the knowledge of the fractional power factor or the scaling exponent.     

Information system for biomedical equipment management in a wide-area environment

An information system used in managing the inventory of equipment at the local health units (LHUs) of the Emilia Romagna region is presented. The system aims at efficient management of information on medical equipment and at supporting regional administrators in financial planning. The system uses ‘classification files’ and ‘working files’. The classification files can be either defined at national (classification of producers, models and equipment types) or local (classification of suppliers and hospital departments) level. The working files are used to store all information necessary for the inventory of equipment in the local health unit (equipment inventory file) and results of automatic annual economic computations (residual values and amortisation quota file). Starting from data stored in the above-mentioned files the system can perform several procedures, such as control on data entry, economic computations and report printings. The main aspects of these operations are described in detail. Finally, some information on biomedical equipment of one of the largest local health units of the Emilia Romagna region, obtained from elaboration of system data, is shown and discussed.     

Haemostatic investigations: The impact of new technologies

Blood loss following trauma is controlled by a complex series of interactions involving the vascular surface, blood platelets and ‘activated’ coagulation factors. Activation of the coagulation cascade involves a series of zymogen to enzyme transformations with each enzyme associating with a co-factor on a ‘surface’ such as negatively charged platelet membrane phospholipid to form reaction complexes. In physiological terms it is possible that this system is continuously switched on producing low levels of activated serine proteases which are continuously being neutralised by protease inhibitors and co-factor neutralising reactions which down-regulate blood clotting processes, thus maintaining patency of the vascular tree. It is in this context that the concept of identifying molecular markers of haemostatic activation is well recognised. The haemostatic investigations now include biochemical and immunological investigations in order to detect small concentrations of products from intravascular thrombin generation, platelet-specific proteins released as a consequence of platelet release reaction, circulating activated clotting factors, activation peptides and ‘activated clotting factor-inhibitor’ complexes. This review will concentrate on new markers of haemostasis which are currently being used in the investigation of thrombosis.     

Persistent dorsal ophthalmic artery and ophthalmic artery arising from the middle meningeal artery diagnosed by MR angiography at 3 T

Introduction

A persistent dorsal ophthalmic artery (OA) is a rare variation that originates from the cavernous segment of the internal carotid artery (ICA) and enters the orbit via the superior orbital fissure (SOF). Occasionally, the OA also arises from the middle meningeal artery (MMA) and enters the orbit via the SOF. These two major variations of the OA have not been well described by magnetic resonance (MR) angiography. We evaluated their prevalence on MR angiography at 3 T.

Methods

We retrospectively reviewed our database of MR angiographic images obtained using a 3 T imager. Of images of 846 patients, we evaluated those of 826 patients (1,652 OAs) with special attention to OA origin and its course into the orbit. We excluded images of the 20 because quality was insufficient to assess.

Results

We found 7 (0.42 %) persistent dorsal OAs among 1,652 OAs (right/left, 6/1; male/female, 3/4). Twenty-four (1.45 %) OAs arose from the MMA (right/left/bilateral, 11/5/4; male/female, 10/10), three of which also demonstrated a small normally branching OA. In one patient, we observed both right persistent dorsal OA and left OA arising from the MMA.

Conclusions

Per OA, the prevalence of persistent dorsal OA was 0.42 % and of OA arising from the MMA, 1.45 %, with a tendency toward right-side predominance. OA arising from the MMA can be seen bilaterally; preprocedural knowledge of this variation is important because of the danger associated with endovascular procedures of the external carotid system when the OA arises from the MMA.     

Experimental and theoretical modelling of intra-aortic balloon pump operation

The performance of intra-aortic balloon pumping is assessed on the basis of a mock circulation and a theoretical model of arterial pulse propagation. The parameters investigated include timing of onset and speed of inflation and deflation as well as pumped air volume. The models used do not contain any active peripheral elements with regulatory capabilities and so the simulated heart adjusts its stroke volume mechanically according to the operating conditions. The observed and calculated changes of typical quantities in terms of ‘stroke’ volume, ‘LV’, ‘aortic’ and ‘peripheral’ pressures are to be attributed, therefore, to the influence of the mechanical pump operation without physiological reactions of the circulatory system as a whole. It is found that timing details of the counterpulsation have a minor influence on the overall mechanical pump performance. Accordingly, the influence of physiological reactions of the cardiovascular system to changes in pump operation seems to be far more important than the one caused by the purely mechanical changes themselves. However, rapid inflation and deflation of the balloon may be accompanied by severe opening or closing shocks, respectively.     

Complimentary Endothelial Cell/Smooth Muscle Cell Co-Culture Systems with Alternate Smooth Muscle Cell Phenotypes

Development of in vitro models of native and injured vasculature is crucial for better understanding altered wound healing in disease, device implantation, or tissue engineering. Conditions were optimized using polyethyleneteraphalate transwell filters for human aortic endothelial cell (HAEC)/smooth muscle cell (HASMC) co-cultures with divergent HASMC phenotypes (‘more or less secretory’) while maintaining quiescent HAECs. Resulting HASMC phenotype was studied at 48 and 72 h following co-culture initiation, and compared to serum and growth factor starved monocultured ‘forced contractile’ HASMCs. Forced contractile HASMCs demonstrated organized α-smooth muscle actin filaments, minimal interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) secretion, and low intracellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and tissue factor expression. Organization of α-smooth muscle actin was lost in ‘more secretory’ HASMCs in co-culture with HAECs, and IL-8 and MCP-1 secretion, as well as ICAM-1, VCAM-1, and tissue factor expression were significantly upregulated at both time points. Alternately, ‘less secretory’ HASMCs in co-culture with HAECs showed similar characteristics to forced contractile HASMCs at the 48 h time point, while by the 72 h time point they behaved similarly to ‘more secretory’ HASMCs. These co-culture systems could be useful in better understanding vascular healing, however there remain time constraint considerations for maintaining culture integrity/cell phenotype.     

Reasons women give for abortion: a review of the literature

The aim was to identify from empirical research that used quantitative or qualitative methods the reasons women give for having an abortion. A search was conducted of peer-reviewed, English language publications indexed in eight computerized databases with publication date 1996–2008, using keywords ‘abortion’ and ‘reason’ (Medline: ‘induced abortion’ OR ‘termination of pregnancy’ OR ‘elective abortion’ and ‘reason’). Inclusion criteria were empirical research on humans that identified women’s reasons for undergoing an abortion, conducted in ‘high-income’ countries. 19 eligible papers were found. Despite variation in methods of generating, collecting, and analysing reasons, and the inadequacy of methodological detail in some papers, all contributed to a consistent picture of the reasons women give for having an abortion, with three main categories (‘Woman-focused’, ‘Other-focused’, and ‘Material’) identified. Ambivalence was often evident in women’s awareness of reasons for continuing the pregnancy, but abortion was chosen because continuing with the pregnancy was assessed as having adverse effects on the life of the woman and significant others. Women’s reasons were complex and contingent, taking into account their own needs, a sense of responsibility to existing children and the potential child, and the contribution of significant others, including the genetic father.     

Intrinsic joint kinematic planning. I: Reassessing the Listing’s law constraint in the control of three-dimensional arm movements

This study tested the validity of the assumption that intrinsic kinematic constraints, such as Listing’s law, can account for the geometric features of three-dimensional arm movements. In principle, if the arm joints follow a Listing’s constraint, the hand paths may be predicted. Four individuals performed ‘extended arm’, ‘radial’, ‘frontal plane’, and ‘random mixed’ movements to visual targets to test Listing’s law assumption. Three-dimensional rotation vectors of the upper arm and forearm were calculated from three-dimensional marker data. Data fitting techniques were used to test Donders’ and Listing’s laws. The coefficient values obtained from fitting rotation vectors to the surfaces described by a second-order equation were analyzed. The results showed that the coefficients that represent curvature and twist of the surfaces were often not significantly different from zero, particularly not during randomly mixed and extended arm movements. These coefficients for forearm rotations were larger compared to those for the upper arm segment rotations. The mean thickness of the rotation surfaces ranged between ≈1.7° and 4.7° for the rotation vectors of the upper arm segment and ≈2.6° and 7.5° for those of the forearm. During frontal plane movements, forearm rotations showed large twist scores while upper arm segment rotations showed large curvatures, although the thickness of the surfaces remained low. The curvatures, but not the thicknesses of the surfaces, were larger for large versus small amplitude radial movements. In conclusion, when examining the surfaces obtained for the different movement types, the rotation vectors may lie within manifolds that are anywhere between curved or twisted manifolds. However, a two-dimensional thick surface may roughly represent a global arm constraint. Our findings suggest that Listing’s law is implemented for some types of arm movement, such as pointing to targets with the extended arm and during radial reaching movements.     

Eye movements during action preparation

Looking at actions of others activates representations of similar own actions, that is, the action resonates. This may facilitate or interfere with the actions that one intends to make. We asked whether people promote or block those effects by making eye movements to or away from the actions of others. We investigated gaze behavior with a cup-clinking task: An actor shown on a video grabbed a cup and moved it toward the participant who next grabbed his own cup in the ‘same’ or in a different, ‘complementary’, way. In the ‘same’ condition, participants mostly looked at the place where the actor held the cup. In the ‘complementary’ condition, gaze behavior was similar at the start of the actor’s action. To our surprise, as the action reached completion, participants started to look at the cup’s site that corresponded to the grabbing instruction for their own action. A second experiment showed that this effect grew with delay of the go-signal. This indicates that a reason for the effect may be to support memorizing the instructed action. The bottom line of the study is that passively viewed scenes (passive in the sense that nothing in the observed scene is manipulated by the viewer) are scanned to support preparation of actions that one intends to make. We discuss how this finding relates to action resonance and how it relates to links between representations of actions and objects.     

Physiological consequences of thin filament cooperativity for vertebrate striated muscle contraction: a theoretical study

Bindings of both myosin and Ca²⁺ to the thin filament of vertebrate striated muscle are known to be strongly cooperative. Here the relation between these two sources of cooperativity and their consequences for physiological properties are assessed by comparing two models, with and without Monod-type myosin-binding cooperativity. In both models a thin filament regulatory unit (RU) is in either ‘off’ or ‘on’ state, and the equilibrium between them (K _on) is [Ca²⁺]-dependent. The calculations predict the following: (1) In both models, myosin binding stabilizes the RU in the ‘on’ state, causing troponin to trap Ca²⁺. This stabilization in turn increases the Ca²⁺-binding cooperativity, ensuring efficient regulation to occur in a narrow [Ca²⁺] range. (2) In the cooperative model, the RU is stabilized with a relatively low myosin affinity for actin (K∼ ∼1), while the non-cooperative model requires a much higher affinity (K∼ ∼ 10) to produce the same effect. (3) The cooperative model reproduces the known effects of [Ca²⁺] on the rate of force development and shortening velocity with a low K, but again the non-cooperative model requires a higher value. (4) Because of the finite value of K _on, the thin filaments can never be fully activated by increasing [Ca²⁺], indicating that contracting muscles are under strong influence of thin-filament cooperativity even at saturating [Ca²⁺]. Interpretation of data on muscle mechanics without considering these cooperative effects could therefore lead to a substantial (10-fold) overestimate of cross-bridge binding properties.