Low-Density EEG Correction With Multivariate Decomposition and Subspace Reconstruction

A hybrid method is proposed for removing artifacts from electroencephalographic (EEG) signals. This relies on the integration of artifact subspace reconstruction (ASR) with multivariate empirical mode decomposition (EMD). The method can be applied when few EEG sensors are available, a condition in which existing techniques are not effective, and it was tested with two public datasets: 1) semisynthetic data and 2) experimental data with artifacts. One to four EEG sensors were taken into account, and the proposal was compared to both ASR and multivariate EMD (MEMD) alone. The proposed method efficiently removed muscular, ocular, or eye-blink artifacts on both semisynthetic and experimental data. Unexpectedly, the ASR alone also showed compatible performance on semisynthetic data. However, ASR did not work properly when experimental data were considered. Finally, MEMD was found less effective than both ASR and MEMD-ASR

Active and Passive Brain-Computer Interfaces Integrated with Extended Reality for Applications in Health 4.0

This paper presents the integration of extended reality (XR) with brain-computer interfaces (BCI) to open up new possibilities in the health 4.0 framework. Such integrated systems are here investigated with respect to an active and a passive BCI paradigm. Regarding the active BCI, the XR part consists of providing visual and vibrotactile feedbacks to help the user during motor imagery tasks. Therefore, XR aims to enhance the neurofeedback by enhancing the user engagement. Meanwhile, in the passive BCI, user engagement monitoring allows the adaptivity of a XR-based rehabilitation game for children. Preliminary results suggest that the XR neurofeedback helps the BCI users to carry on motor imagery tasks with up to 84% classification accuracy, and that the level of emotional and cognitive engagement can be detected with an accuracy greater than 75%

Paving the Way for Motor Imagery-Based Tele-Rehabilitation through a Fully Wearable BCI System

The present study introduces a brain–computer interface designed and prototyped to be wearable and usable in daily life. Eight dry electroencephalographic sensors were adopted to acquire the brain activity associated with motor imagery. Multimodal feedback in extended reality was exploited to improve the online detection of neurological phenomena. Twenty-seven healthy subjects used the proposed system in five sessions to investigate the effects of feedback on motor imagery. The sample was divided into two equal-sized groups: a “neurofeedback” group, which performed motor imagery while receiving feedback, and a “control” group, which performed motor imagery with no feedback. Questionnaires were administered to participants aiming to investigate the usability of the proposed system and an individual’s ability to imagine movements. The highest mean classification accuracy across the subjects of the control group was about 62% with 3% associated type A uncertainty, and it was 69% with 3% uncertainty for the neurofeedback group. Moreover, the results in some cases were significantly higher for the neurofeedback group. The perceived usability by all participants was high. Overall, the study aimed at highlighting the advantages and the pitfalls of using a wearable brain–computer interface with dry sensors. Notably, this technology can be adopted for safe and economically viable tele-rehabilitation

Multimodal Feedback in Assisting a Wearable Brain-Computer Interface Based on Motor Imagery

A multimodal sensory feedback was exploited in the present study to improve the detection of neurological phenomena associated with motor imagery. At this aim, visual and haptic feedback were simultaneously delivered to the user of a brain-computer interface. The motor imagery-based brain-computer interface was built by using a wearable and portable electroencephalograph with only eight dry electrodes, a haptic suit, and a purposely implemented virtual reality application. Preliminary experiments were carried out with six subjects participating in five sessions on different days. The subjects were randomly divided into “control group” and “neurofeedback group”. The former performed pure motor imagery without receiving any feedback, while the latter received multimodal feedback as a response to their imaginative act. Results of a cross validation showed that at most 61% of classification accuracy was achieved in performing the pure motor imagination. On the contrary, subjects of the “neurofeedback group” achieved up to 82% mean accuracy, with a peak of 91% in one of the sessions. However, no improvement in pure motor imagery was observed, either when practicing with pure motor imagery or with feedback

Real-time estimation of EEG-based engagement in different tasks

: Objective.Recent trends in brain-computer interface (BCI) research concern the passive monitoring of brain activity, which aim to monitor a wide variety of cognitive states. Engagement is such a cognitive state, which is of interest in contexts such as learning, entertainment or rehabilitation. This study proposes a novel approach for real-time estimation of engagement during different tasks using electroencephalography (EEG).Approach.Twenty-three healthy subjects participated in the BCI experiment. A modified version of the d2 test was used to elicit engagement. Within-subject classification models which discriminate between engaging and resting states were trained based on EEG recorded during a d2 test based paradigm. The EEG was recorded using eight electrodes and the classification model was based on filter-bank common spatial patterns and a linear discriminant analysis. The classification models were evaluated in cross-task applications, namely when playing Tetris at different speeds (i.e. slow, medium, fast) and when watching two videos (i.e. advertisement and landscape video). Additionally, subjects' perceived engagement was quantified using a questionnaire.Main results.The models achieved a classification accuracy of 90% on average when tested on an independent d2 test paradigm recording. Subjects' perceived and estimated engagement were found to be greater during the advertisement compared to the landscape video (p= 0.025 andp<0.001, respectively); greater during medium and fast compared to slow Tetris speed (p<0.001, respectively); not different between medium and fast Tetris speeds. Additionally, a common linear relationship was observed for perceived and estimated engagement (rrm= 0.44,p<0.001). Finally, theta and alpha band powers were investigated, which respectively increased and decreased during more engaging states.Significance.This study proposes a task-specific EEG engagement estimation model with cross-task capabilities, offering a framework for real-world applications

How to successfully classify EEG in motor imagery BCI: a metrological analysis of the state of the art

Objective. Processing strategies are analyzed with respect to the classification of electroencephalographic signals related to brain-computer interfaces (BCIs) based on motor imagery (MI). A review of literature is carried out to understand the achievements in MI classification, the most promising trends, and the challenges in replicating these results. Main focus is placed on performance by means of a rigorous metrological analysis carried out in compliance with the international vocabulary of metrology. Hence, classification accuracy and its uncertainty are considered, as well as repeatability and reproducibility.Approach.The paper works included in the review concern the classification of electroencephalographic signals in motor-imagery-based BCIs. Article search was carried out in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses standard and 89 studies were included.Main results.Statistically-based analyses show that brain-inspired approaches are increasingly proposed, and that these are particularly successful in discriminating against multiple classes. Notably, many proposals involve convolutional neural networks. Instead, classical machine learning approaches are still effective for binary classifications. Many proposals combine common spatial pattern, least absolute shrinkage and selection operator, and support vector machines. Regarding reported classification accuracies, performance above the upper quartile is in the 85%-100% range for the binary case and in the 83%-93% range for multi-class one. Associated uncertainties are up to 6% while repeatability for a predetermined dataset is up to 8%. Reproducibility assessment was instead prevented by lack of standardization in experiments.Significance.By relying on the analyzed studies, the reader is guided towards the development of a successful processing strategy as a crucial part of a BCI. Moreover, it is suggested that future studies should extend these approaches on data from more subjects and with custom experiments, even by investigating online operation. This would also enable the quantification of the results reproducibility

Online processing for motor imagery-based brain-computer interfaces relying on EEG

This manuscript reports a comparison among three possible strategies for online processing of electroencephalo-graphic signals, in terms of their impact on the online classification accuracy. The comparison was carried out in the framework of brain-computer interfaces based on motor imagery. Filter bank common spatial pattern was exploited as a standard feature extraction technique along with a support vector machine for classification of the brain signals. This machine learning-based algorithm was trained offline and evaluated on independent evaluation data by means of the online processing strategies. Benchmark dataset were used, so that the online processing performance was compared to reference offline performances compatible with literature (at least 74 % classification accuracy). Results suggest that it is convenient to use the bigger part of the imagery period in training the algorithm prior to online classification accuracy. Moreover, using an enlarging window for evaluation appeared to be the best strategy to remain close to reference mean accuracy

Visual and haptic feedback in detecting motor imagery within a wearable brain-computer interface

This paper presents a wearable brain–computer interface relying on neurofeedback in extended reality for the enhancement of motor imagery training. Visual and vibrotactile feedback modalities were evaluated when presented either singularly or simultaneously. Only three acquisition channels and state-of-the-art vibrotactile chest-based feedback were employed. Experimental validation was carried out with eight subjects participating in two or three sessions on different days, with 360 trials per subject per session. Neurofeedback led to statistically significant improvement in performance over the two/three sessions, thus demonstrating for the first time functionality of a motor imagery-based instrument even by using an utmost wearable electroencephalograph and a commercial gaming vibrotactile suit. In the best cases, classification accuracy exceeded 80 % with more than 20 % improvement with respect to the initial performance. No feedback modality was generally preferable across the cohort study, but it is concluded that the best feedback modality may be subject-dependent

Conceptual design of a machine learning-based wearable soft sensor for non-invasive cardiovascular risk assessment

The number of elderly people is increasing, and heart diseases are a major issue in a healthy aging of population. Indeed, the possibility of hospital care is limited and the avoidance of crowded hospitals recently became even more essential. Meanwhile, the possibility to exploit e-health technology for home care would be desirable. In this framework, the concept design of a soft sensor for measuring cardiovascular risk of a patient in real time is here reported. ECG, blood oxygenation, body temperature, and data acquired from patients’ interviews are processed to extract characterizing features. These are then classified to assess the cardiovascular risk. Experimental results show that patients’ classification accuracy can be as high as 80% when employing a random forest classifier, even with few data employed for training. Finally, method evaluation was extended by exploiting further data and by means of a noise robustness test