Artifacts

2017 ◽  
pp. 98-127
Author(s):  
Riitta Hari ◽  
Aina Puce
Keyword(s):  
Data Analysis ◽  
Eye Movements ◽  
Cardiac Activity ◽  
Signal Space Separation ◽  
Eeg Data ◽  
Eeg Recordings ◽  
Power Line Noise ◽  
Post Hoc ◽  
Space Separation ◽  
The Brain

This chapter focuses on different types of biological and nonbiological artifacts in MEG and EEG recordings, and discusses methods for their recognition and removal. Examples are given of various physiological artifacts, including eye movements, eyeblinks, saccades, muscle, and cardiac activity. Nonbiological artifacts, such as power-line noise, are also demonstrated. Some examples are given to illustrate how these unwanted signals can be identified and removed from MEG and EEG signals with methods such as independent component analysis (as applied to EEG data) and temporal signal-space separation (applied to MEG data). However, prevention of artifacts is always preferable to removing or compensating for them post hoc during data analysis. The chapter concludes with a discussion of how to ensure that signals are emanating from the brain and not from other sources.

scholarly journals A two for one special: EEG hyperscanning using a single-person EEG recording setup

2021 ◽  
Author(s):  
Caitriona Douglas ◽  
Antoine Tremblay ◽  
Aaron J Newman
Keyword(s):  
Event Related Potential ◽  
Oscillatory Activity ◽  
Simultaneous Acquisition ◽  
Single Person ◽  
Eeg Data ◽  
Stimulus Timing ◽  
Audio Data ◽  
Eeg Recordings ◽  
Post Hoc ◽  
Precise Time

EEG hyperscanning refers to recording electroencephalographic (EEG) data from multiple participants simultaneously. Many hyperscanning experimental designs seek to mimic naturalistic behavior, relying on unpredictable participant-generated stimuli. The majority of this research has focused on neural oscillatory activity that is quantified over hundreds of milliseconds or more. This contrasts with traditional event-related potential (ERP) research in which analysis focuses on transient responses, often only tens of milliseconds in duration. Deriving ERPs requires precise time-locking between stimuli and EEG recordings, and thus typically relies on pre-set stimuli that are presented to participants by a system that controls stimulus timing and synchronization with an EEG system. EEG hyperscanning methods typically use separate EEG amplifiers for each participant, increasing cost and complexity — including challenges in synchronizing data between systems. Here, we describe a method that allows for simultaneous acquisition of EEG data from a pair of participants engaged in conversation, using a single EEG system with simultaneous audio data collection that is synchronized with the EEG recording. This allows for the post-hoc insertion of trigger codes so that it is possible to analyze ERPs time-locked to specific events. We further demonstrate methods for deriving ERPs elicited by another person’s spontaneous speech, using this setup.

scholarly journals EEG Deblurring Techniques in a Clinical Context

2004 ◽  
Vol 43 (01) ◽  
pp. 114-117 ◽  
Author(s):  
F. Cincotti ◽  
C. Babiloni ◽  
C. Miniussi ◽  
F. Carducci ◽  
D. Moretti ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Magnetic Resonance Images ◽  
Head Model ◽  
Clinical Environment ◽  
Clinical Context ◽  
Time Period ◽  
Realistic Head Model ◽  
Eeg Data ◽  
Eeg Recordings ◽  
The Brain

Summary Objectives: EEG scalp potential distributions recorded in humans are affected by low spatial resolution and by the dependence on the electrical reference used. High resolution EEG technologies are available to drastically increase the spatial resolution of the raw EEG. Such technologies include the computation of surface Laplacian (SL) of the recorded potentials, as well as the use of realistic head models to estimate the cortical sources via linear inverse procedure (low resolution brain electromagnetic tomography, LORETA). However, these deblurring procedures are generally used in conjunction with EEG recordings with 64-128 scalp electrodes and with realistic head models obtained via sequential magnetic resonance images (MRIs) of the subjects. Such recording setup it is not often available in the clinical context, due to both the unavailability of these technologies and the scarce compliance of the patients with them. In this study we addressed the use of SL and LORETA deblurring techniques to analyze data from a standard 10-20 system (19 electrodes) in a group of Alzheimer disease (AD) patients. Methods: EEG data related to unilateral finger movements were gathered from 10 patients affected by AD. SL and LORETA techniques were applied for source estimation of EEG data. The use of MRIs for the construction of head models was avoided by using the quasi-realistic head model of the Brain Imaging Neurology Institute of Montreal. Results: A similar cortical activity estimated by the SL and LORETA techniques was observed during an identical time period of the acquired EEG data in the examined population. Conclusions: The results of the present study suggest that both SL and LORETA approaches can be usefully applied in the clinical context, by using quasi-realistic head modeling and a standard 10-20 system as electrode montage (19 electrodes). These results represent a reciprocal cross-validation of the two mathematically independent techniques in a clinical environment.

scholarly journals Conditional Entropy: A Potential Digital Marker for Stress

Entropy ◽  
2021 ◽  
Vol 23 (3) ◽  
pp. 286
Author(s):  
Soheil Keshmiri
Keyword(s):  
Resting State ◽  
Nearest Neighbor ◽  
Brain Activity ◽  
Solution Concept ◽  
Conditional Entropy ◽  
K Nearest Neighbor ◽  
Brain Response ◽  
Substantial Progress ◽  
Eeg Recordings ◽  
The Brain

Recent decades have witnessed a substantial progress in the utilization of brain activity for the identification of stress digital markers. In particular, the success of entropic measures for this purpose is very appealing, considering (1) their suitability for capturing both linear and non-linear characteristics of brain activity recordings and (2) their direct association with the brain signal variability. These findings rely on external stimuli to induce the brain stress response. On the other hand, research suggests that the use of different types of experimentally induced psychological and physical stressors could potentially yield differential impacts on the brain response to stress and therefore should be dissociated from more general patterns. The present study takes a step toward addressing this issue by introducing conditional entropy (CE) as a potential electroencephalography (EEG)-based resting-state digital marker of stress. For this purpose, we use the resting-state multi-channel EEG recordings of 20 individuals whose responses to stress-related questionnaires show significantly higher and lower level of stress. Through the application of representational similarity analysis (RSA) and K-nearest-neighbor (KNN) classification, we verify the potential that the use of CE can offer to the solution concept of finding an effective digital marker for stress.

scholarly journals Millimeter (MM) wave and microwave frequency radiation produce deeply penetrating effects: the biology and the physics

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Martin L. Pall
Keyword(s):  
Magnetic Fields ◽  
Electric Fields ◽  
Cardiac Activity ◽  
Maximum Level ◽  
Voltage Sensor ◽  
The Body ◽  
Time Varying ◽  
The Brain ◽  
Mm Waves

Abstract Millimeter wave (MM-wave) electromagnetic fields (EMFs) are predicted to not produce penetrating effects in the body. The electric but not magnetic part of MM-EMFs are almost completely absorbed within the outer 1 mm of the body. Rodents are reported to have penetrating MM-wave impacts on the brain, the myocardium, liver, kidney and bone marrow. MM-waves produce electromagnetic sensitivity-like changes in rodent, frog and skate tissues. In humans, MM-waves have penetrating effects including impacts on the brain, producing EEG changes and other neurological/neuropsychiatric changes, increases in apparent electromagnetic hypersensitivity and produce changes on ulcers and cardiac activity. This review focuses on several issues required to understand penetrating effects of MM-waves and microwaves: 1. Electronically generated EMFs are coherent, producing much higher electrical and magnetic forces then do natural incoherent EMFs. 2. The fixed relationship between electrical and magnetic fields found in EMFs in a vacuum or highly permeable medium such as air, predicted by Maxwell’s equations, breaks down in other materials. Specifically, MM-wave electrical fields are almost completely absorbed in the outer 1 mm of the body due to the high dielectric constant of biological aqueous phases. However, the magnetic fields are very highly penetrating. 3. Time-varying magnetic fields have central roles in producing highly penetrating effects. The primary mechanism of EMF action is voltage-gated calcium channel (VGCC) activation with the EMFs acting via their forces on the voltage sensor, rather than by depolarization of the plasma membrane. Two distinct mechanisms, an indirect and a direct mechanism, are consistent with and predicted by the physics, to explain penetrating MM-wave VGCC activation via the voltage sensor. Time-varying coherent magnetic fields, as predicted by the Maxwell–Faraday version of Faraday’s law of induction, can put forces on ions dissolved in aqueous phases deep within the body, regenerating coherent electric fields which activate the VGCC voltage sensor. In addition, time-varying magnetic fields can directly put forces on the 20 charges in the VGCC voltage sensor. There are three very important findings here which are rarely recognized in the EMF scientific literature: coherence of electronically generated EMFs; the key role of time-varying magnetic fields in generating highly penetrating effects; the key role of both modulating and pure EMF pulses in greatly increasing very short term high level time-variation of magnetic and electric fields. It is probable that genuine safety guidelines must keep nanosecond timescale-variation of coherent electric and magnetic fields below some maximum level in order to produce genuine safety. These findings have important implications with regard to 5G radiation.

scholarly journals Utility of temporally-extended signal space separation algorithm for magnetic noise from vagal nerve stimulators

2013 ◽  
Vol 124 (7) ◽  
pp. 1277-1282 ◽  
Author(s):  
Yosuke Kakisaka ◽  
John C. Mosher ◽  
Zhong I. Wang ◽  
Kazutaka Jin ◽  
Anne-Sophie Dubarry ◽  
...  
Keyword(s):  
Vagal Nerve ◽  
Magnetic Noise ◽  
Separation Algorithm ◽  
Signal Space ◽  
Signal Space Separation ◽  
Space Separation

Calibration of a multichannel MEG system based on the Signal Space Separation method

2012 ◽  
Vol 57 (15) ◽  
pp. 4855-4870 ◽  
Author(s):  
F Chella ◽  
F Zappasodi ◽  
L Marzetti ◽  
S Della Penna ◽  
V Pizzella
Keyword(s):  
Separation Method ◽  
Signal Space ◽  
Signal Space Separation ◽  
Space Separation

A DEEP BREATHING EXERCISE MANAGEMENT IN ARCHERY TO MEMORIZING AL-QUR'AN TO STUDENT OF TAHFIDZ QUR'AN AT SMP AD-DHUHA JEMBER

2021 ◽  
Vol 2 (1) ◽  
pp. 1-6
Author(s):  
Akhmad Efrizal Amrullah ◽  
Ridlo Hafidz Faqih ◽  
Miftakhur Rohman ◽  
Candra Aditya Hermansyah
Keyword(s):  
Data Analysis ◽  
Design Method ◽  
Memory Capacity ◽  
Rank Test ◽  
P Value ◽  
Deep Breathing ◽  
Brain Oxygenation ◽  
Breathing Exercises ◽  
Quasi Experimental ◽  
The Brain

Memorizing Al-Qur'an is an effort to maintain the purity of the Al-Qur'an. The Qur'an tahfidz program is one of the activities intended to prevent the Qur'an from changing and falsifying either partially or completely. As the name implies, this program is applied to tahfidz Qur'an student to memorize Al-Qur'an under the guidance of their teacher. Memorization ability is determined by memory capacity which indicates brain health, one of which is influenced by the supply of oxygen to the brain. One way to maintain brain oxygenation is the management of deep breathing exercises combined with archery. The purpose of this study was to determine the effect of deep breathing exercises management in archery to achievement of memorizing the Qur'an. This research was held at SMP Ad-Dhuha Jember with a quasi-experimental one group pretest-posttest design method and was conducted in April-June 2019. The type of sample used was a total sampling of 34 respondents. Data analysis used the Wilcoxon Signed-Rank Test. The results showed an increase in the achievement of memorizing Al-Qur'an among students of the tahfidz Qur'an after managing deep breathing exercises with archery. Data analysis with alpha (α) <0.05 indicates a p value of 0.000 so that Ho is rejected. Thus there is an effect of deep breathing exercises management in archery on the achievement of memorizing the Al-Qur'an. A strong memory is needed to keep memorizing Al-Qur'an. To help increase the memory capacity of the brain, it requires an adequate supply of oxygen. Deep breathing exercises management combined with archery can be a way to maintain brain oxygenation. This exercise focuses on fullfiling oxygen needs, which in the process of memorizing the brain's memory functions are widely used.

A fuzzy sensitivity analysis approach to estimate brain effective connectivity and its application to epileptic seizure detection

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Nader Moharamzadeh ◽  
Ali Motie Nasrabadi
Keyword(s):  
Time Series ◽  
Sensitivity Analysis ◽  
Effective Connectivity ◽  
Multivariate Time Series ◽  
Inference System ◽  
Eeg Data ◽  
Adaptive Neurofuzzy Inference System ◽  
Intracranial Electroencephalography ◽  
Fuzzy Network ◽  
The Brain

Abstract The brain is considered to be the most complicated organ in human body. Inferring and quantification of effective (causal) connectivity among regions of the brain is an important step in characterization of its complicated functions. The proposed method is comprised of modeling multivariate time series with Adaptive Neurofuzzy Inference System (ANFIS) and carrying out a sensitivity analysis using Fuzzy network parameters as a new approach to introduce a connectivity measure for detecting causal interactions between interactive input time series. The results of simulations indicate that this method is successful in detecting causal connectivity. After validating the performance of the proposed method on synthetic linear and nonlinear interconnected time series, it is applied to epileptic intracranial Electroencephalography (EEG) signals. The result of applying the proposed method on Freiburg epileptic intracranial EEG data recorded during seizure shows that the proposed method is capable of discriminating between the seizure and non-seizure states of the brain.

scholarly journals Migraine with Prolonged Aura: Correlation of Clinical and EEG Features

1995 ◽  
Vol 8 (2) ◽  
pp. 109-114 ◽  
Author(s):  
A. O. Ogunyemi
Keyword(s):  
Cerebral Cortex ◽  
Migraine With Aura ◽  
Slow Waves ◽  
Spreading Cortical Depression ◽  
Eeg Abnormalities ◽  
Cortical Depression ◽  
Eeg Changes ◽  
Eeg Recordings ◽  
The Brain

Migraine with prolonged aura has rarely been examined with regard to the sequence of the neurological symptoms and the associated EEG changes. This report describes five patients who underwent clinical assessment and EEG recordings during attacks of migraine with prolonged aura. CT scan of the brain was obtained in four of them. Follow-up EEG was also obtained. The aura symptoms either preceded the headache or were coincident with it. The aura symptoms evolved in a manner consistent with posterior-to-anterior dysfunction of the cerebral cortex. The EEG abnormalities were non-epileptiform and consisted of focal delta slow waves or theta slow waves. The EEG abnormalities showed good correlation with the patients' aura symptoms and resolved when the patients became symptom free. The posterior-to-anterior sequence of the aura symptoms is in accord with the findings during cerebral blood flow studies in patients having migraine with aura. Also the symptoms and EEG changes in our patients indicate dysfunction of the cerebral cortex, consistent with the notion that spreading cortical depression may be the underlying pathophysiological event in migraine with aura.

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