389 research outputs found
Artifact Removal Methods in EEG Recordings: A Review
To obtain the correct analysis of electroencephalogram (EEG) signals, non-physiological and physiological artifacts should be removed from EEG signals. This study aims to give an overview on the existing methodology for removing physiological artifacts, e.g., ocular, cardiac, and muscle artifacts. The datasets, simulation platforms, and performance measures of artifact removal methods in previous related research are summarized. The advantages and disadvantages of each technique are discussed, including regression method, filtering method, blind source separation (BSS), wavelet transform (WT), empirical mode decomposition (EMD), singular spectrum analysis (SSA), and independent vector analysis (IVA). Also, the applications of hybrid approaches are presented, including discrete wavelet transform - adaptive filtering method (DWT-AFM), DWT-BSS, EMD-BSS, singular spectrum analysis - adaptive noise canceler (SSA-ANC), SSA-BSS, and EMD-IVA. Finally, a comparative analysis for these existing methods is provided based on their performance and merits. The result shows that hybrid methods can remove the artifacts more effectively than individual methods
Motion Artifacts Correction from Single-Channel EEG and fNIRS Signals using Novel Wavelet Packet Decomposition in Combination with Canonical Correlation Analysis
The electroencephalogram (EEG) and functional near-infrared spectroscopy
(fNIRS) signals, highly non-stationary in nature, greatly suffers from motion
artifacts while recorded using wearable sensors. This paper proposes two robust
methods: i) Wavelet packet decomposition (WPD), and ii) WPD in combination with
canonical correlation analysis (WPD-CCA), for motion artifact correction from
single-channel EEG and fNIRS signals. The efficacy of these proposed techniques
is tested using a benchmark dataset and the performance of the proposed methods
is measured using two well-established performance matrices: i) Difference in
the signal to noise ratio ({\Delta}SNR) and ii) Percentage reduction in motion
artifacts ({\eta}). The proposed WPD-based single-stage motion artifacts
correction technique produces the highest average {\Delta}SNR (29.44 dB) when
db2 wavelet packet is incorporated whereas the greatest average {\eta} (53.48%)
is obtained using db1 wavelet packet for all the available 23 EEG recordings.
Our proposed two-stage motion artifacts correction technique i.e. the WPD-CCA
method utilizing db1 wavelet packet has shown the best denoising performance
producing an average {\Delta}SNR and {\eta} values of 30.76 dB and 59.51%,
respectively for all the EEG recordings. On the other hand, the two-stage
motion artifacts removal technique i.e. WPD-CCA has produced the best average
{\Delta}SNR (16.55 dB, utilizing db1 wavelet packet) and largest average {\eta}
(41.40%, using fk8 wavelet packet). The highest average {\Delta}SNR and {\eta}
using single-stage artifacts removal techniques (WPD) are found as 16.11 dB and
26.40%, respectively for all the fNIRS signals using fk4 wavelet packet. In
both EEG and fNIRS modalities, the percentage reduction in motion artifacts
increases by 11.28% and 56.82%, respectively when two-stage WPD-CCA techniques
are employed.Comment: 25 pages, 10 figures and 2 table
Noise removal methods on ambulatory EEG: A Survey
Over many decades, research is being attempted for the removal of noise in
the ambulatory EEG. In this respect, an enormous number of research papers is
published for identification of noise removal, It is difficult to present a
detailed review of all these literature. Therefore, in this paper, an attempt
has been made to review the detection and removal of an noise. More than 100
research papers have been discussed to discern the techniques for detecting and
removal the ambulatory EEG. Further, the literature survey shows that the
pattern recognition required to detect ambulatory method, eye open and close,
varies with different conditions of EEG datasets. This is mainly due to the
fact that EEG detected under different conditions has different
characteristics. This is, in turn, necessitates the identification of pattern
recognition technique to effectively distinguish EEG noise data from a various
condition of EEG data
Study and analysis of motion artifacts for ambulatory electroencephalography
Motion artifacts contribute complexity in acquiring clean electroencephalography (EEG) data. It is one of the major challenges for ambulatory EEG. The performance of mobile health monitoring, neurological disorders diagnosis and surgeries can be significantly improved by reducing the motion artifacts. Although different papers have proposed various novel approaches for removing motion artifacts, the datasets used to validate those algorithms are questionable. In this paper, a unique EEG dataset was presented where ten different activities were performed. No such previous EEG recordings using EMOTIV EEG headset are available in research history that explicitly mentioned and considered a number of daily activities that induced motion artifacts in EEG recordings. Quantitative study shows that in comparison to correlation coefficient, the coherence analysis depicted a better similarity measure between motion artifacts and motion sensor data. Motion artifacts were characterized with very low frequency which overlapped with the Delta rhythm of the EEG. Also, a general wavelet transform based approach was presented to remove motion artifacts. Further experiment and analysis with more similarity metrics and longer recording duration for each activity is required to finalize the characteristics of motion artifacts and henceforth reliably identify and subsequently remove the motion artifacts in the contaminated EEG recordings
An EEG-based perceptual function integration network for application to drowsy driving
© 2015 Elsevier B.V. All rights reserved. Drowsy driving is among the most critical causes of fatal crashes. Thus, the development of an effective algorithm for detecting a driver's cognitive state demands immediate attention. For decades, studies have observed clear evidence using electroencephalography that the brain's rhythmic activities fluctuate from alertness to drowsiness. Recognition of this physiological signal is the major consideration of neural engineering for designing a feasible countermeasure. This study proposed a perceptual function integration system which used spectral features from multiple independent brain sources for application to recognize the driver's vigilance state. The analysis of brain spectral dynamics demonstrated physiological evidenced that the activities of the multiple cortical sources were highly related to the changes of the vigilance state. The system performances showed a robust and improved accuracy as much as 88% higher than any of results performed by a single-source approach
Advanced Pipelines For Artifact Removal From EEG Data
Feature extraction and working with EEG data has become one the most
challenging studies these years. The raw EEG signal has various artifacts and
needs to be detected and separated from brain components. This study is part of
ERC. For removing artifacts from EEG data , this procedure done by a method
known as “semi-automatic ICs selection pipeline”.This method was developed
and verified by Cosynclab directed by Prof. Betti in Rome (where I spent my
internship). In particular, the thesis work aims to investigate another method for
complementing semi-automatic ICs selection pipeline and evaluate results
which conveys to increasing the accuracy of semi-automatic ICs selection
pipeline.The ICA algorithm derives independent sources from highly correlated
EEG signals statistically without concern for the actual location or configuration
of the EEG signal source . It is used to locate concurrent signal sources that are
either too close together or too broadly scattered to be separated using
conventional localization techniques. The primary issue in understanding ICA
output is determining the right dimension of the input channels and the
physiological and/or psychophysiological relevance of the resulting ICA source
channels.With semi-automatic ICs selection pipeline method more than 2600
ICs evaluated and 405 ICs labeled as brains and the rest classified as artifacts.
To evaluate these 405 ICs and increase possible accuracy another method was
used known as ICLabel. ICLabel projects had been proposed by EEGLAB. This
is a method based on Deep Learning and provides classification based on EEG
IC classifier1
. After running and comparing the two methods pipeline, then,we
designed an application for comparison and visualization output for both
methods which name is IC selection.With this application we realize some
modification needed for future steps for labeling with semi-automatic ICs
selection pipeline method and some artifacts could change from artifacts to
brain.Feature extraction and working with EEG data has become one the most
challenging studies these years. The raw EEG signal has various artifacts and
needs to be detected and separated from brain components. This study is part of
ERC. For removing artifacts from EEG data , this procedure done by a method
known as “semi-automatic ICs selection pipeline”.This method was developed
and verified by Cosynclab directed by Prof. Betti in Rome (where I spent my
internship). In particular, the thesis work aims to investigate another method for
complementing semi-automatic ICs selection pipeline and evaluate results
which conveys to increasing the accuracy of semi-automatic ICs selection
pipeline.The ICA algorithm derives independent sources from highly correlated
EEG signals statistically without concern for the actual location or configuration
of the EEG signal source . It is used to locate concurrent signal sources that are
either too close together or too broadly scattered to be separated using
conventional localization techniques. The primary issue in understanding ICA
output is determining the right dimension of the input channels and the
physiological and/or psychophysiological relevance of the resulting ICA source
channels.With semi-automatic ICs selection pipeline method more than 2600
ICs evaluated and 405 ICs labeled as brains and the rest classified as artifacts.
To evaluate these 405 ICs and increase possible accuracy another method was
used known as ICLabel. ICLabel projects had been proposed by EEGLAB. This
is a method based on Deep Learning and provides classification based on EEG
IC classifier1
. After running and comparing the two methods pipeline, then,we
designed an application for comparison and visualization output for both
methods which name is IC selection.With this application we realize some
modification needed for future steps for labeling with semi-automatic ICs
selection pipeline method and some artifacts could change from artifacts to
brain
Analysis of Dynamic Brain Imaging Data
Modern imaging techniques for probing brain function, including functional
Magnetic Resonance Imaging, intrinsic and extrinsic contrast optical imaging,
and magnetoencephalography, generate large data sets with complex content. In
this paper we develop appropriate techniques of analysis and visualization of
such imaging data, in order to separate the signal from the noise, as well as
to characterize the signal. The techniques developed fall into the general
category of multivariate time series analysis, and in particular we extensively
use the multitaper framework of spectral analysis. We develop specific
protocols for the analysis of fMRI, optical imaging and MEG data, and
illustrate the techniques by applications to real data sets generated by these
imaging modalities. In general, the analysis protocols involve two distinct
stages: `noise' characterization and suppression, and `signal' characterization
and visualization. An important general conclusion of our study is the utility
of a frequency-based representation, with short, moving analysis windows to
account for non-stationarity in the data. Of particular note are (a) the
development of a decomposition technique (`space-frequency singular value
decomposition') that is shown to be a useful means of characterizing the image
data, and (b) the development of an algorithm, based on multitaper methods, for
the removal of approximately periodic physiological artifacts arising from
cardiac and respiratory sources.Comment: 40 pages; 26 figures with subparts including 3 figures as .gif files.
Originally submitted to the neuro-sys archive which was never publicly
announced (was 9804003
AUTOMATED ARTIFACT REMOVAL AND DETECTION OF MILD COGNITIVE IMPAIRMENT FROM SINGLE CHANNEL ELECTROENCEPHALOGRAPHY SIGNALS FOR REAL-TIME IMPLEMENTATIONS ON WEARABLES
Electroencephalogram (EEG) is a technique for recording asynchronous activation of neuronal firing inside the brain with non-invasive scalp electrodes. EEG signal is well studied to evaluate the cognitive state, detect brain diseases such as epilepsy, dementia, coma, autism spectral disorder (ASD), etc. In this dissertation, the EEG signal is studied for the early detection of the Mild Cognitive Impairment (MCI). MCI is the preliminary stage of Dementia that may ultimately lead to Alzheimers disease (AD) in the elderly people. Our goal is to develop a minimalistic MCI detection system that could be integrated to the wearable sensors. This contribution has three major aspects: 1) cleaning the EEG signal, 2) detecting MCI, and 3) predicting the severity of the MCI using the data obtained from a single-channel EEG electrode. Artifacts such as eye blink activities can corrupt the EEG signals. We investigate unsupervised and effective removal of ocular artifact (OA) from single-channel streaming raw EEG data. Wavelet transform (WT) decomposition technique was systematically evaluated for effectiveness of OA removal for a single-channel EEG system. Discrete Wavelet Transform (DWT) and Stationary Wavelet Transform (SWT), is studied with four WT basis functions: haar, coif3, sym3, and bior4.4. The performance of the artifact removal algorithm was evaluated by the correlation coefficients (CC), mutual information (MI), signal to artifact ratio (SAR), normalized mean square error (NMSE), and time-frequency analysis. It is demonstrated that WT can be an effective tool for unsupervised OA removal from single channel EEG data for real-time applications.For the MCI detection from the clean EEG data, we collected the scalp EEG data, while the subjects were stimulated with five auditory speech signals. We extracted 590 features from the Event-Related Potential (ERP) of the collected EEG signals, which included time and spectral domain characteristics of the response. The top 25 features, ranked by the random forest method, were used for classification models to identify subjects with MCI. Robustness of our model was tested using leave-one-out cross-validation while training the classifiers. Best results (leave-one-out cross-validation accuracy 87.9%, sensitivity 84.8%, specificity 95%, and F score 85%) were obtained using support vector machine (SVM) method with Radial Basis Kernel (RBF) (sigma = 10, cost = 102). Similar performances were also observed with logistic regression (LR), further validating the results. Our results suggest that single-channel EEG could provide a robust biomarker for early detection of MCI. We also developed a single channel Electro-encephalography (EEG) based MCI severity monitoring algorithm by generating the Montreal Cognitive Assessment (MoCA) scores from the features extracted from EEG. We performed multi-trial and single-trail analysis for the algorithm development of the MCI severity monitoring. We studied Multivariate Regression (MR), Ensemble Regression (ER), Support Vector Regression (SVR), and Ridge Regression (RR) for multi-trial and deep neural regression for the single-trial analysis. In the case of multi-trial, the best result was obtained from the ER. In our single-trial analysis, we constructed the time-frequency image from each trial and feed it to the convolutional deep neural network (CNN). Performance of the regression models was evaluated by the RMSE and the residual analysis. We obtained the best accuracy with the deep neural regression method
Concurrent fNIRS and EEG for brain function investigation: A systematic, methodology-focused review
Electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) stand as state-of-the-art techniques for non-invasive functional neuroimaging. On a unimodal basis, EEG has poor spatial resolution while presenting high temporal resolution. In contrast, fNIRS offers better spatial resolution, though it is constrained by its poor temporal resolution. One important merit shared by the EEG and fNIRS is that both modalities have favorable portability and could be integrated into a compatible experimental setup, providing a compelling ground for the development of a multimodal fNIRS-EEG integration analysis approach. Despite a growing number of studies using concurrent fNIRS-EEG designs reported in recent years, the methodological reference of past studies remains unclear. To fill this knowledge gap, this review critically summarizes the status of analysis methods currently used in concurrent fNIRS-EEG studies, providing an up-to-date overview and guideline for future projects to conduct concurrent fNIRS-EEG studies. A literature search was conducted using PubMed and Web of Science through 31 August 2021. After screening and qualification assessment, 92 studies involving concurrent fNIRS-EEG data recordings and analyses were included in the final methodological review. Specifically, three methodological categories of concurrent fNIRS-EEG data analyses, including EEG-informed fNIRS analyses, fNIRS-informed EEG analyses, and parallel fNIRS-EEG analyses, were identified and explained with detailed description. Finally, we highlighted current challenges and potential directions in concurrent fNIRS-EEG data analyses in future research
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