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1.
Medicine (Baltimore) ; 99(46): e23116, 2020 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-33181681

RESUMO

A recent paper in the journal Neuroreport suggested that, upon source localization, the semantic P600 localizes to executive function areas, that is, outside language. But is this true for all types of linguistic P600? We report a cross-sectional source localization study of a classical (agreement) syntactic paradigm.The results show a clear localization to the temporal lobe, in classical language areas.The P600 is probably not a unitary phenomenon in term of source localization, and the question whether it localizes within or outside the language system depends on the type of P600.


Assuntos
Mapeamento Encefálico/métodos , Potenciais Evocados/fisiologia , Idioma , Semântica , Lobo Temporal , Adulto , Compreensão/fisiologia , Eletroencefalografia/métodos , Fenômenos Eletromagnéticos , Feminino , Humanos , Masculino , Estimulação Luminosa/métodos , Lobo Temporal/diagnóstico por imagem , Lobo Temporal/fisiopatologia , Tomografia/métodos
2.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 1027-1030, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018160

RESUMO

Empathy which can understand and respond to the unique affective experiences of others plays an essential role in social interaction. Although many neuroimaging studies have investigated the neural mechanisms underlying empathy for social pain, how its mechanisms are modulated by trait empathy remains unknown. The present event-related potential (ERP) study used Chatroom Interact Task to examine how trait empathy modulates brain response to empathy for social rejection. The behavior results showed that participants were less pleasant when observing rejection compared to observing acceptance in both high- and low-levels empathy groups. The ERP results revealed more negative-going N2 for social acceptance compared to rejection in both groups, but there was no difference in N2 between high- and low- empathy group. However, the late components, i.e., the P3b, N400 and LPP, revealed significant difference between social acceptance and rejection in high empathic participants rather than low empathic participants. These findings suggested that individuals with high empathic traits could devote more attention and mental resources to process observing ostracism.


Assuntos
Empatia , Distância Social , Encéfalo , Eletroencefalografia , Potenciais Evocados , Feminino , Humanos , Masculino
3.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2475-2478, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018508

RESUMO

Cervical vagus nerve stimulation (VNS) is a neuromodulation therapy used in the treatment of several chronic disorders. In order to maximize the therapeutic effectiveness of VNS, it has become increasingly important to deliver fiber-specific neurostimulation, so that undesired effects can be minimized. Assessing the activation of different vagal fiber types through electrical stimulation is therefore essential for developing fiber-selective VNS therapies. Towards this goal, we conducted in silico investigations using a generic model of functionally distinct nerve fibers and clinically relevant cuff electrodes using COMSOL. Our model is constrained by histological observations from rat cervical vagus nerves and its outputs are validated against averaged compound nerve action potentials (CNAPs) obtained from rat vagus nerve recordings. We propose this model as an effective tool to design fiber-specific stimulation protocols before testing them in experimental animals.


Assuntos
Estimulação do Nervo Vago , Nervo Vago , Animais , Potenciais Evocados , Pescoço , Fibras Nervosas , Ratos
4.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2528-2531, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018521

RESUMO

Surgical removal of the seizure onset zone (SOZ) in epilepsy patients is a potentially curative treatment, but the process heavily relies on accurate localization of the SOZ via visual inspection. SPES (Single-pulse electrical stimulation) is a method recently used to explore inter-areal connectivity in vivo to probe functional brain networks such as language and motor networks, and to a much lesser degree, seizure networks. We hypothesized that a dynamical quantification of the connectivity networks derived from the evoked responses induced by SPES could also be used to localize the SOZ. To test our hypothesis, we used an intracranial EEG (iEEG) data set in which five epilepsy patients underwent extensive SPES evaluation. For each patient, and for each dataset that stimulated a different pair of electrodes, we constructed a state-space model from the patient's data. Specifically, we simultaneously estimated model parameters under an exogenous pulse input to a dynamical system whose state vector consisted of the response iEEG signals. Then, the size of the reachable state space, as quantified by the maximum singular value of the reachability matrix, σmax(R), was computed and denoted as the "largest" network response possible when stimulating the given pair. Our results suggest high agreement between σmax(R) and clinically annotated SOZ for patients with localizable SOZs.Clinical Relevance- Our study applies dynamical systems theory to identify epileptogenic brain regions, creating a novel tool that clinicians may use in surgical planning for medically-refractory epilepsy patients.


Assuntos
Epilepsia Resistente a Medicamentos , Convulsões , Animais , Encéfalo , Eletrocorticografia , Potenciais Evocados , Humanos
5.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2857-2860, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018602

RESUMO

Parkinson's disease (PD) is a complex neurode-generative disorder that results into poverty of movements. Freezing of gait (FOG) is a common and severely incapacitating symptom of PD. However, the underlying neurophysiological mechanism of FOG is still unclear. Electroencephalogram (EEG) as a non-invasive brain signal measurement method has been repeatedly used to reveal the pathological reasons behind PD. Since PD affects movement abilities, one particular type of EEG pattern called Movement-related cortical potential (MRCP), which was shown to be related to the generation of movement intention, can be a useful tool in PD research. However, most MRCP studies in PD area focus on the upper-limb movement like finger movement, to the best knowledge of the authors, no study explored MRCP characteristics during lower extremity movement in PD patients, particularly PD patients with FOG. This paper intends to investigate the relationship between the characteristics of MRCP and FOG by comparing MRCP signals among three groups: healthy controls group, PD patients without FOG group, and PD patients with FOG group. These three groups of participants were recruited based on age-matching and gender proportion matching criteria. During the experiment, the Electromyography (EMG) from the tibialis anterior (TA) muscle and EEG were recorded when performing ankle dorsiflexion (AD) by the dominant foot. MRCP signals were extracted from EEG data based on the muscle activities in the TA muscle of the dominant foot. The results of this study show that, during lower limb activities, MRCP shares considerable similarities between PD patients and healthy participants. However, the amplitude of MRCP in PD patients (with and without FOG) is lower compared to the healthy participants. In addition, direct observations from the results show that MRCP from PD patients with FOG has higher amplitude but more variability in terms of amplitude and latency than those from PD patients without FOG.


Assuntos
Transtornos Neurológicos da Marcha , Doença de Parkinson , Potenciais Evocados , Marcha , Humanos , Movimento
6.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2877-2880, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018607

RESUMO

Error-related potentials (ErrPs) can reflect the brain's response to errors. Recently, it has been used in the studies on neural mechanisms of human cognition, such as error detection and conflict monitoring. Moreover, ErrPs have provided technical support for the development of brain-computer interface (BCI). However, the different effects of visual stimulation modes (dynamic or static) on ErrPs have not been revealed. This may seriously affect the recognition accuracy of the ErrPs in practical applications. Therefore, the aim of this study was to investigate how people respond to different types of visual stimulations. Nineteen participants were recruited in the ErrPs-based tasks with two visual stimulation modes (dynamic and static). The ErrPs were analyzed and the feature values (N1, P2, P3, N6 and P8, named by the occurrence time) were statistically compared. The results showed that the difference between correctness and error was reflected in P3, N6, P8 in dynamic stimulation; and N1, P3, N6 and P8 in static stimulation. In the event-related potential based on error, the differences between dynamic and static tasks were reflected in N1 and P2. In conclusion, this study found that the features with later occurrence were significantly affected by correctness and error in both cases, while the error-related change in N1 only existed under the static stimulation. We also found that the recognition of stimulation modes came earlier within about 300 ms after the start of visual stimulation.


Assuntos
Interfaces Cérebro-Computador , Eletroencefalografia , Encéfalo , Potenciais Evocados , Humanos , Estimulação Luminosa
7.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2885-2888, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018609

RESUMO

Human Machine Interfaces (HMIs) can provide critical support and improve daily task functionality for prosthesis users or social interaction for patients with locked-in syndrome using an assistive communication device. One goal in the development of sophisticated HMIs is to reduce the cognitive load (CL) they place on the user to promote the use of the technology. Electroencephalogram (EEG)-derived measures collected with wired wet-electrode systems have been used to assess CL in laboratory environments and have demonstrated acceptable test-retest reliability. Assessment of CL during real-world unconstrained HMI operation, however, requires the use of a wireless dry-electrode EEG system which provides easier electrode application and untethered movement. However, the test-retest reliability of wireless dry-electrode systems to quantify CL has not been explored. Ensuring the consistent capture of CL-related signals across multiple sessions is critical if these devices are to be used to assess how improvements in HMIs affect CL. Therefore, the current study used a wireless dry-electrode EEG system to compare Evoked Response Potential (ERP) features of a simple auditory oddball task to measure CL during two separate testing sessions a week apart. ERPs of 11 subjects were recorded while participants performed a virtual task at two difficulty levels. A significant correlation was found between the P300 component of the ERPs and subjective ratings of CL during both testing sessions. Furthermore, there was a statistically significant test-retest reliability for this same ERP feature and similar signal-to-noise ratios (SNRs) across sessions.Clinical Relevance- This is an initial step in validating wireless dry-electrode EEG systems to assess cognitive load across multiple sessions. The evidence presented is critical if dry-wireless EEG systems are to be used to identify aspects of HMIs that reduce CL in clinical and real-life environments. Assessing CL in unconstrained environments can better inform clinicians and technology developers in their design of future HMIs.


Assuntos
Eletroencefalografia , Potenciais Evocados , Cognição , Eletrodos , Humanos , Reprodutibilidade dos Testes
8.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2973-2976, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018630

RESUMO

Event-related potential (ERP) speller can be utilized in device control and communication for locked-in or severely injured patients. However, problems such as inter-subject performance instability and ERP-illiteracy are still unresolved. Therefore, it is necessary to predict classification performance before performing an ERP speller in order to use it efficiently. In this study, we investigated the correlations with ERP speller performance using a resting-state before an ERP speller. In specific, we used spectral power and functional connectivity according to four brain regions and five frequency bands. As a result, the delta power in the frontal region and functional connectivity in the delta, alpha, gamma bands are significantly correlated with the ERP speller performance. Also, we predicted the ERP speller performance using EEG features in the resting-state. These findings may contribute to investigating the ERP-illiteracy and considering the appropriate alternatives for each user.


Assuntos
Interfaces Cérebro-Computador , Encéfalo , Eletroencefalografia , Potenciais Evocados , Lobo Frontal , Humanos
9.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3003-3006, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018637

RESUMO

Exploring the brain response to stimuli of healthy people in passive state is helpful to understand the brain response mechanism of unresponsive people. Event-related potential (ERP) can reflect the time synchronization of potentials, which is a feasible objective electrophysiological index reflecting the functional status of the brain. In this paper, we used the subjects' own name (SON) as target stimuli and compared with the nontarget stimuli (others' name) of Three Chinese Characters (3CC) and Two Chinese Characters (2CC) with the same stimuli duration (600ms) and inter stimuli interval (500ms-800ms). Thirteen healthy subjects attended in this study with four conditions ( [active, passive]×[3CC, 2CC] ). We compared the ERP waveforms, the behavior performance, and the classification of four different conditions. ERP results show that the P300 amplitude of conditions with 3CC nontargets is higher than that of conditions with 2CC nontargets. Behavioral results show that the grand accuracy is 97% when the nontargets are 3CC, while the grand accuracy is only 94% when the nontargets are 2CC. The reaction time is also different from the two nontargets (605ms with 3CC vs 635ms with 2CC). Classification results illustrate that in active condition, the accuracy rate is 82.1% when the nontarget is 3CC, and that is 80.9% in passive condition, which are 4.2% and 6.4% higher than the accuracy rate under 2CC cases in both active and passive conditions. This study can provide a scheme for grading diagnosis of consciousness detection, and further applying to clinical evaluation.Clinical Relevance- This study can provide a better paradigm basis for clinical evaluation of unresponsive patients (such as disorder of consciousness, DOC) and may become an effective auxiliary means for clinical rating scales.


Assuntos
Potencial Evocado P300 , Potenciais Evocados , Encéfalo , Potenciais Evocados Auditivos , Potenciais Evocados Visuais , Humanos
10.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3216-3219, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018689

RESUMO

Real-time monitoring of mental workload (MWL) is a crucial step to build closed-loop adaptive aiding systems for human-machine systems. MWL estimators based on spontaneous electroencephalography (EEG) and event-related potentials (ERPs) have shown great potentials to achieve this goal. However, the previous studies show that the between-task robustness of these EEG/ERP-based MWL estimators is still an unsolved intractable question. This study attempts to examine the task-irrelevant auditory event-related potentials (tir-aERPs) as MWL indicators. A working memory task (verbal n-back) and a visuo-motor task (multi-attribute task battery, MATB), both with two difficulty levels (easy and hard), were used in the experiment, along with task-irrelevant auditory probes that did not need any response from the participants. EEG was recorded from ten participants when they were performing the tasks. The tir-aERPs elicited by the auditory probes were extracted and analyzed. The results show that the amplitudes of N1, early P3a (eP3a) and the late reorienting negativity (RON) significantly decreased with the increasing MWL in both n-back and MATB. Task type has no obvious influence on the amplitudes and topological layout of the MWL-sensitive tir-aERPs features. These results suggest that the tir-aERPs are potentially more constant MWL indicators across very different task types. Therefore, the tir-aERPs should be taken into consideration in future task-independent MWL monitoring studies.


Assuntos
Eletroencefalografia , Potenciais Evocados , Humanos , Memória de Curto Prazo , Carga de Trabalho
11.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3477-3480, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018752

RESUMO

New methods for the analysis of electrically-evoked compound action potentials (eCAPs) are described. Mammalian nerves tend to have broad multi-modal distributions of fibre diameters, which translates into a spread of conduction velocities. The method of velocity selective recording (VSR) is unable to distinguish between this spectral spread and the transfer function of the system. The concept of the velocity impulse function (VIF) is introduced as a tool to differentiate between these signal and system attributes. The new methods enable separate estimates of velocity spectral broadening and signal-to-noise ratio (SNR) to be obtained.


Assuntos
Potenciais Evocados , Potenciais de Ação , Animais
12.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3553-3556, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018770

RESUMO

Transcranial direct current stimulation (tDCS) provides a non-invasive approach to modulate brain functions. Some studies have shown that tDCS combined with working memory training can alter the effect of training. This study aims to investigate the effect of HD-tDCS over the left dorsolateral prefrontal cortex combined with N-back task on the amplitude of event related potentials (ERP). In the experiment, subjects performed N-back training for 30min every day with active or sham tDCS for 10 days. EEG data were recorded when subjects performing N-back tests prior to the training, 1 day and 20 days post the training, respectively. With the analyses of ERP components, it was found that there were no significant differences between active and sham groups. However, the results of post-test were significantly different from the pre-test. Subsequently, both in active group and in sham group, the amplitude of ERP increased in the frontoparietal and occipital regions 1 day post training. Those alterations were enhanced 20 days post training in the active group but not in the sham group. The results indicated the aftereffect of HD-tDCS to promote the effects of cognitive training, showing accumulative positive aftereffects on ERP 20 days after the stimulation.


Assuntos
Estimulação Transcraniana por Corrente Contínua , Potenciais Evocados , Aprendizagem , Memória de Curto Prazo , Córtex Pré-Frontal
13.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 553-556, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018049

RESUMO

The growing interest in the study of functional brain-heart interplay (BHI) has motivated the development of novel methodological frameworks for its quantification. While a combination of electroencephalography (EEG) and heartbeat-derived series has been widely used, the role of EEG preprocessing on a BHI quantification is yet unknown. To this extent, here we investigate on four different EEG electrical referencing techniques associated with BHI quantifications over 4-minute resting-state in 15 healthy subjects. BHI methods include the synthetic data generation model, heartbeat-evoked potentials, heartbeat-evoked oscillations, and maximal information coefficient (MIC). EEG signals were offline referenced under the Cz channel, common average, mastoids average, and Laplacian method, and statistical comparisons were performed to assess similarities between references and between BHI techniques. Results show a topographical agreement between BHI estimation methods depending on the specific EEG reference. Major differences between BHI methods occur with the Laplacian reference, while major differences between EEG references are with the MIC analysis. We conclude that the choice of EEG electrical reference may significantly affect a functional BHI quantification.


Assuntos
Encéfalo , Eletroencefalografia , Eletricidade , Potenciais Evocados , Voluntários Saudáveis , Humanos
14.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 1019-1022, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018158

RESUMO

The N2pc event-related potential component measures direction and time course of selective visual attention and represents an important biomarker in cognitive neuroscience. While its subtractive origin strongly influences the amplitude, thus hindering its detection, other external factors, such as subject's inefficiency to allocate attention to the cued target, or the heterogeneity of the visual context, may strongly affect the elicitation of the component itself. It would therefore be extremely important to create a tool that, using as few sweeps as possible, could reliably establish whether an N2pc is present in an individual subject. In the present work, we propose an approach by resorting to a time-frequency analysis of N2pc individual signals; in particular, power at each frequency band (α/ß/δ/θ) was computed in the N2 time range and correlated to the estimated amplitude of the N2pc. Preliminary results on fourteen human volunteers of a visual search design showed a very high correlation coefficient (over 0.9) between the low frequency bands power and the mean absolute amplitude of the component, using only 40 sweeps. Results also seemed to suggest that N2pc amplitude values higher than 0.5 µV could be accurately classified according to time-frequency indices.Clinical Relevance - The online detection of the N2pc presence in individual EEG datasets would allow not only to study the factors responsible of N2pc variability across subjects and conditions, but also to investigate novel search variants on participants with a predisposition to show an N2pc, reducing time and costs and the possibility to obtain biased results.


Assuntos
Neurociência Cognitiva , Eletroencefalografia , Atenção , Sinais (Psicologia) , Potenciais Evocados , Humanos
15.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2861-2864, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018603

RESUMO

Decoding olfactory cognition has been generating significant interest in recent years due to a wide range of applications, from diagnosing neurodegenerative disorders to consumer research and traditional medicine. In this study, we have investigated whether changes in odor stimuli evaluation across repeated stimuli presentation can be attributed to changes in brain perception of the stimuli. Epoch intervals representing olfactory sensory perception were extracted from electroencephalography (EEG) signals using minimum variance distortionless response (MVDR)-based single trial event related potential (ERP) approach to understand the evoked response to high pleasantness and low pleasantness stimuli. We found statistically significant changes in self reported stimuli evaluation between initial and final trials (p < 0.05) for both stimuli categories. However, the changes in ERP amplitude were found to be statistically significant only for the high pleasantness stimuli. This implies that olfactory stimuli of higher hedonic value recruit high-order cognitive processing that may be responsible for initial increased ERP response, as well as for rapid subsequent adaptation in processing the stimuli.


Assuntos
Potenciais Evocados , Odorantes , Encéfalo , Eletroencefalografia , Humanos , Olfato
16.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3260-3263, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018700

RESUMO

Auditory stream segregation is an important function of the auditory system, and the extent to which this function works has a major impact on listener's ability to recognize auditory objects in complex listening environments. However, cochlear implant (CI) listeners are poorly equipped for this challenge, mainly owing to the impoverished sensory information available via their implants. The purpose of this study was to examine two factors, i.e., frequency separation and time interval, affecting the auditory stream segregation in vocoder simulations simulating CI speech processing based on an event-related potential (ERP) experiment. The pure-tone stimuli were processed by a vocoding process, and presented to normal-hearing listeners in an ERP experiment. Experimental results showed that a large frequency separation or a short time interval led to a larger mismatch negativity (MMN) response. The MMN results in this work suggested that the degree of auditory stream segregation was affected by frequency separation and time interval, and MMN could serve as a potential index for future ERP studies on auditory stream segregation in CI users.


Assuntos
Implante Coclear , Implantes Cocleares , Estimulação Acústica , Percepção Auditiva , Potenciais Evocados , Humanos
17.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 4745-4748, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33019051

RESUMO

Brain-computer interfaces (BCIs) allow for translating electroencephalogram (EEG) into control commands, e.g., to control a quadcopter. This study, we developed a practical BCI based on steady-state visually evoked potential (SSVEP) for continuous control of a quadcopter from the first-person perspective. Users watched with the video stream from a camera on the quadcopter. An innovative user interface was developed by embedding 12 SSVEP flickers into the video stream, which corresponded to the flight commands of 'take-off,' 'land,' 'hover,' 'keep-going,' 'clockwise,' 'counter-clockwise' and rectilinear motions in six directions, respectively. The command was updated every 400ms by decoding the collected EEG data using a combined classification algorithm based on task-related component analysis (TRCA) and linear discriminant analysis (LDA). The quadcopter flew in the 3-D space according to the control vector that was determined by the latest four commands. Three novices participated in this study. They were asked to control the quadcopter by either the brain or hands to fly through a circle and land on the target zone. As a result, the time consumption ratio of brain-control to hand-control was as low as 1.34, which means the BCI performance was close to hands. The information transfer rate reached a peak of 401.79 bits/min in the simulated online experiment. These results demonstrate the proposed SSVEP-BCI system is efficient for controlling the quadcopter.


Assuntos
Interfaces Cérebro-Computador , Eletroencefalografia , Potenciais Evocados , Potenciais Evocados Visuais , Humanos , Movimento (Física)
18.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 4055-4058, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018889

RESUMO

Recent mobile and wearable electroencephalogram (EEG)-sensing technologies have been demonstrated to be effective for measuring rapid changes of spatio-spectral EEG correlates of brain and cognitive functions of interest with more ecologically natural settings. However, commercial EEG products are available commonly with a fixed headset in terms of the number of electrodes and their locations to the scalp practically constrains their generalizability for different demands of EEG and brain-computer interface (BCI) study. While most progress focused on innovation of sensing hardware and conductive electrodes, less effort has been done to renovate mechanical structures of an EEG headset. Recently, an electrode-holder assembly infrastructure was designed to be capable of unlimitedly (re)assembling a desired n-channel electrode headset through a set of primary elements (i.e., LEGO-like headset). The present work empirically demonstrated one of its advantage regarding coordinating the homogeneous or heterogeneous sensors covering the target regions of the brain. Towards this objective, an 8-channel LEGO headset was assembled to conduct a simultaneous event-related potential (ERP) recording of the wet- and dry-electrode EEG systems and testify their signal quality during standing still versus treadmill walking. The results showed that both systems returned a comparable P300 signal-to-noise ratio (SNR) for standing, yet the dry system was more susceptible to the movement artifacts during slow walking. The LEGO headset infrastructure facilitates a desired benchmark study, e.g., comparing the signal quality of different electrodes on non-stationary subjects conducted in this work, or a specific EEG and BCI application.


Assuntos
Interfaces Cérebro-Computador , Caminhada , Eletrodos , Eletroencefalografia , Potenciais Evocados
19.
PLoS One ; 15(9): e0239612, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32966341

RESUMO

Diverse psychological mechanisms have been associated with modulations of different EEG frequencies. To the extent of our knowledge, there are few studies of the test-retest reliability of these modulations in the human brain. To assess evoked and induced alpha reliabilities related to cognitive processing, EEG data from twenty subjects were recorded in 58 derivations in two different sessions separated by 49.5 ± 48.9 (mean ± standard deviation) days. A visual oddball was selected as the cognitive task, and three main parameters were analyzed for evoked and induced alpha modulations (latency, amplitude and topography). Latency and amplitude for evoked and induced modulations showed stable behavior between the two sessions. The correlation between sessions for alpha evoked and induced topographies in the grand average (group level) was r = 0.923, p<0.001; r = 0.962, p<0.001, respectively. The within-subject correlation values for evoked modulation ranged from 0.472 to 0.974 (mean: 0.766), whereas induced activity showed a different range, 0.193 to 0.892 (mean: 0.655). Individual analysis of the test-retest reliability showed a higher heterogeneity in the induced modulation, probably due to the heterogeneous phases found in the second case. However, despite this heterogeneity in phase values for induced activity relative to the onset of the stimuli, an excellent correlation score was obtained for group topography, with values that were better than those of the grand average evoked topography. As a main conclusion, induced alpha activity can be observed as a stable and reproducible response in the cognitive processing of the human brain.


Assuntos
Ritmo alfa , Eletroencefalografia/normas , Potenciais Evocados , Adulto , Variação Biológica Individual , Encéfalo/fisiologia , Eletroencefalografia/métodos , Feminino , Humanos , Masculino , Reprodutibilidade dos Testes
20.
PLoS One ; 15(9): e0238872, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32915850

RESUMO

Association between electroencephalography (EEG) and individually personal information is being explored by the scientific community. Though person identification using EEG is an attraction among researchers, the complexity of sensing limits using such technologies in real-world applications. In this research, the challenge has been addressed by reducing the complexity of the brain signal acquisition and analysis processes. This was achieved by reducing the number of electrodes, simplifying the critical task without compromising accuracy. Event-related potentials (ERP), a.k.a. time-locked stimulation, was used to collect data from each subject's head. Following a relaxation period, each subject was visually presented a random four-digit number and then asked to think of it for 10 seconds. Fifteen trials were conducted with each subject with relaxation and visual stimulation phases preceding each mental recall segment. We introduce a novel derived feature, dubbed Inter-Hemispheric Amplitude Ratio (IHAR), which expresses the ratio of amplitudes of laterally corresponding electrode pairs. The feature was extracted after expanding the training set using signal augmentation techniques and tested with several machine learning (ML) algorithms, including Linear Discriminant Analysis (LDA), Support Vector Machine (SVM), and k-Nearest Neighbor (kNN). Most of the ML algorithms showed 100% accuracy with 14 electrodes, and according to our results, perfect accuracy can also be achieved using fewer electrodes. However, AF3, AF4, F7, and F8 electrode combination with kNN classifier which yielded 99.0±0.8% testing accuracy is the best for person identification to maintain both user-friendliness and performance. Surprisingly, the relaxation phase manifested the highest accuracy of the three phases.


Assuntos
Algoritmos , Identificação Biométrica/métodos , Encéfalo/fisiologia , Eletroencefalografia/métodos , Potenciais Evocados , Processamento de Imagem Assistida por Computador/métodos , Aprendizado de Máquina , Adulto , Análise Discriminante , Eletrodos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estimulação Luminosa , Máquina de Vetores de Suporte , Adulto Jovem
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