Electroencephalography (EEG) is a non-invasive technique used to record cortical neurons' electrical activity using electrodes placed on the scalp. It has become a promising avenue for research ...beyond state-of-the-art EEG research that is conducted under static conditions. EEG signals are always contaminated by artifacts and other physiological signals. Artifact contamination increases with the intensity of movement.
In the last decade (since 2010), researchers have started to implement EEG measurements in dynamic setups to increase the overall ecological validity of the studies. Many different methods are used to remove non-brain activity from the EEG signal, and there are no clear guidelines on which method should be used in dynamic setups and for specific movement intensities.
Currently, the most common methods for removing artifacts in movement studies are methods based on independent component analysis. However, the choice of method for artifact removal depends on the type and intensity of movement, which affects the characteristics of the artifacts and the EEG parameters of interest. When dealing with EEG under non-static conditions, special care must be taken already in the designing period of an experiment. Software and hardware solutions must be combined to achieve sufficient removal of unwanted signals from EEG measurements.
We have provided recommendations for the use of each method depending on the intensity of the movement and highlighted the advantages and disadvantages of the methods. However, due to the current gap in the literature, further development and evaluation of methods for artifact removal in EEG data during locomotion is needed.
This review examined 83 articles using neuroimaging modalities to investigate the neural correlates underlying static and dynamic human balance control, with aims to support future mobile ...neuroimaging research in the balance control domain. Furthermore, this review analyzed the mobility of the neuroimaging hardware and research paradigms as well as the analytical methodology to identify and remove movement artifact in the acquired brain signal. We found that the majority of static balance control tasks utilized mechanical perturbations to invoke feet-in-place responses (27 out of 38 studies), while cognitive dual-task conditions were commonly used to challenge balance in dynamic balance control tasks (20 out of 32 studies). While frequency analysis and event related potential characteristics supported enhanced brain activation during static balance control, that in dynamic balance control studies was supported by spatial and frequency analysis. Twenty-three of the 50 studies utilizing EEG utilized independent component analysis to remove movement artifacts from the acquired brain signals. Lastly, only eight studies used truly mobile neuroimaging hardware systems. This review provides evidence to support an increase in brain activation in balance control tasks, regardless of mechanical, cognitive, or sensory challenges. Furthermore, the current body of literature demonstrates the use of advanced signal processing methodologies to analyze brain activity during movement. However, the static nature of neuroimaging hardware and conventional balance control paradigms prevent full mobility and limit our knowledge of neural mechanisms underlying balance control.
Cutaneous ultrasonography can be challenging in children. We aim to identify the most complicated cases and the best timing for assessment.
We retrospectively reviewed sonographic exams in pediatric ...patients from our cutaneous ultrasonography clinic over a two-year period. Movement artifacts were classified according to their consequences and their frequency was studied in relation to the age of the patient, location of the lesion, and underlying pathology.
The overall frequency of exams affected by movement artifacts was 16.76% (91/543) and all belonged to children younger than 4 years of age. The frequency of impaired sonographies was particularly low in patients aged 0 to 4 months (12.77%; 6/47) and particularly high in children aged from 4 to 12 months (56.60%; 60/106). Regarding location, exams were more frequently disadvantaged when assessing the head and neck area (44.53%; 61/137). In relation to pathology, developmental anomalies showed a significantly higher frequency of exams damaged by movement artifacts (41.82%; 23/55).
Cutaneous ultrasonography without sedation can be particularly difficult in children aged between 4 and 12 months, especially when lesions are located on the head and neck and a Doppler exam is required. When assessing congenital lesions, the first four months of life are ideal for a first examination.
Continuous-wave near-infrared spectroscopy and imaging enable tissue hemodynamics and oxygenation to be determined non-invasively. Movements of the investigated subject can cause movement artifacts ...(MAs) in the recorded signals. The strength and type of MAs induced depend on the measurement principle. The aim of the present study was to investigate the quantitative relationship between different single-distance (SD) and multi-distance (MD) measurement methods and their susceptibility to MAs. We found that each method induces MAs to a different degree, and that MD methods are more robust against MAs than SD methods.
The widespread use of remote technology has moved medical care services into individuals’ homes. In this perspective, the ubiquitous computing research proposes self-management and remote monitoring ...to help patients with healthcare in low-cost everyday home usage systems based on the latest technological advances in sensors, communication, and portability. This work analyzes recent publications on the paradigm of continuous monitoring through wearable and portable systems, focusing on photoplethysmography (PPG) advances and referencing the current systematic study proposed by Fine et al. The study revised the literature highlighting the pros and cons of using the PPG system for fitness, wellbeing, and medical devices. However, future works should focus on the standardization of the practical use and assessment of the quality of the PPGs’ output. For clinical parameter extraction methodology in terms of biological sites of application and signal processing methods, PPG is the most convenient and widely used system potentially suitable for the decentralized paradigm of continuous monitoring healthcare concepts.
Abstract The use of surface electromyography (SEMG) in vibration studies is problematic since motion artifacts occupy the same frequency band with the SEMG signal containing information on ...synchronous motor unit activity. We hypothesize that using a harsher, 80–500 Hz band-pass filter and using rectification can help eliminate motion artifacts and provide a way to observe synchronous motor unit activity that is phase locked to vibration using SEMG recordings only. Multi Motor Unit (MMU) action potentials using intramuscular electrodes along with SEMG were recorded from the gastrocnemius medialis (GM) of six healthy male volunteers. Data were collected during whole body vibration, using vibration frequencies of 30 Hz, 35 Hz, 40 Hz or 50 Hz. A computer simulation was used to investigate the efficacy of filtering under different scenarios: with or without artifacts and/or motor unit synchronization. Our findings indicate that motor unit synchronization took place during WBV as verified by MMU recordings. A harsh filtering regimen along with rectification proved successful in demonstrating motor unit synchronization in SEMG recordings. Our findings were further supported by the results from the computer simulation, which indicated that filtering and rectification was efficient in discriminating motion artifacts from motor unit synchronization. We suggest that the proposed signal processing technique may provide a new methodology to evaluate the effects of vibration treatments using only SEMG. This is a major advantage, as this non-intrusive method is able to overcome movement artifacts and also indicate the synchronization of underlying motor units.
Movement-Related effects in fMRI time-series Friston, Karl J.; Williams, Steven; Howard, Robert ...
Magnetic resonance in medicine,
March 1996, Letnik:
35, Številka:
3
Journal Article
Recenzirano
This paper concerns the spatial and intensity transformations that are required to adjust for the confounding effects of subject movement during functional MRI (fMRI) activation studies. An approach ...is presented that models, and removes, movement‐related artifacts from fMRI time‐series. This approach is predicated on the observation that movement‐related effects are extant even after perfect realignment. Movement‐related effects can be divided into those that are a function of position of the object in the frame of reference of the scanner and those that are due to movement in previous scans. This second component depends on the history of excitation experienced by spins in a small volume and consequent differences in local saturation. The spin excitation history thus will itself be a function of previous positions, suggesting an autoregression‐moving average model for the effects of previous displacements on the current signal. A model is described as well as the adjustments for movement‐related components that ensue. The empirical analyses suggest that (in extreme situations) over 90% of fMRI signal can be attributed to movement, and that this artifactual component can be successfully removed.
Electroencephalogram(EEG) signal is often contaminated by electronic noise as well as movement artifacts. This paper presented an algorithm based on Canonical correlation analysis(CCA) to estimate ...multichannel EEG data. Different from previous studies, in which CCA was mainly used to detect the invariant features specific to each brain state, in this paper, the canonical variates computed by CCA were used to reconstruct the multi-channel EEG data. Firstly, two data sets, EEG signals and the reference signals based on prior knowledge were constructed. Next, canonical variates were computed by pro jecting the two data sets onto basis vectors. Finally,a least squares solution was used to estimate the multichannel EEG data. The experiment results suggested that the algorithm is capable of reconstructing the actual specific components with high quality. We also hint future possible application of the algorithm in the estimation of functional connectivity patterns at the end of the paper.
▶ Motor fMRI is invariably affected by movement artifacts. Most algorithms in literature were designed for slow changes of head position over several brain scans. ▶ This paper introduces a simple ...model-based method to remove motion artifacts during short duration movements. ▶ The proposed algorithm can account for head movement and field deformations due to movement, within and outside of the scanner's field of view. ▶ It uses information from the experimental design and subject kinematics to focus the artifact attenuation in time and space and minimize the loss of uncorrupted data. ▶ Applications of the algorithm on arm reaching experimental data obtained with blocked and event-related designs demonstrate attenuation of motion artifacts with minimal effect on the brain activations.
Behavioral analysis of multi-joint arm reaching has allowed important advances in understanding the control of voluntary movements. Complementing this analysis with functional magnetic resonance imaging (fMRI) would give insight into the neural mechanisms behind this control. However, fMRI is very sensitive to artifacts created by head motion and magnetic field deformation caused by the moving limbs. It is thus necessary to attenuate these motion artifacts in order to obtain correct activation patterns. Most algorithms in literature were designed for slow changes of head position over several brain scans and are not very effective on data when the movement is of duration below the resolution of a brain scan. This paper introduces a simple model-based method to remove motion artifacts during short duration movements. The proposed algorithm can account for head movement and field deformations due to movements within and outside of the scanner's field of view. It uses information from the experimental design and subject kinematics to focus the artifact attenuation in time and space and minimize the loss of uncorrupted data. Applications of the algorithm on arm reaching experimental data obtained with blocked and event-related designs demonstrate attenuation of motion artifacts with minimal effect on the brain activations.
Abstract Background/purpose Skin marker-based systems are used to accurately measure the three-dimensional motion of the temporomandibular joint. Since skin markers move relative to the underlying ...bone during jaw movements, the measured temporomandibular joint kinematics is subject to soft-tissue artifacts. A complete evaluation of soft-tissue artifacts for markers on the facial anatomical landmarks and on an optical frame during jaw opening/closing movements is not available. The purpose of this study was to further our knowledge using a commercial opto-electronic movement tracking system to measure marker movements, that were then compared to true values defined by a transoral rigid device attached to the incisors. Materials and methods Twenty healthy subjects performed jaw opening/closing movements at a self-selected pace while the 3D trajectories of 17 facial skin markers, three markers on an optical frame, and 4 markers on a transoral device were measured using a six-camera opto-electronic motion tracking system. Movements of the skin and optical frame markers relative to the head coordinate system defined by the transoral device (gold standard) were calculated. The movements of the head coordinate systems defined using different groups of skin markers relative to the gold standard were also analyzed. Results The results showed that nose-bridge markers had minimal displacements but the middle- and side-face markers had large displacements. Conclusions It appears that markers on the frontal nose bridge are good alternatives to transoral rigid devices for measuring mandibular motion, compared to optical frame markers and other skin markers on the face. The results of the current study will be helpful for establishing guidelines for marker placement when measuring mandibular movements in patients with potential temporomandibular disorders.
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