Biophysical Aspects of EEG and MEG Generation

2017 ◽  
Author(s):  
Wytse J. Wadman ◽  
Fernando H. Lopes da Silva
Keyword(s):  
Electromagnetic Fields ◽  
Maxwell Equations ◽  
Brain Activity ◽  
Electrical Field ◽  
The Third ◽  
Scalp Eeg ◽  
External Electromagnetic Fields ◽  
The Common ◽  
The Brain ◽  
Physical Principles

This chapter reviews the essential physical principles involved in the generation of electroencephalographic (EEG) and magnetoencephalographic (MEG) signals. The general laws governing the electrophysiology of neuronal activity are analyzed within the formalism of the Maxwell equations that constitute the basis for understanding electromagnetic fields in general. Three main topics are discussed. The first is the forward problem: How can one calculate the electrical field that results from a known configuration of neuronal sources? The second is the inverse problem: Given an electrical field as a function of space and time mostly recorded at the scalp (EEG/MEG), how can one reconstruct the underlying generators at the brain level? The third is the reverse problem: How can brain activity be modulated by external electromagnetic fields with diagnostic and/or therapeutic objectives? The chapter emphasizes the importance of understanding the common biophysical framework concerning these three main topics of brain electrical and magnetic activities.

Causes and Consequences of Sports Concussion

2014 ◽  
Vol 42 (2) ◽  
pp. 128-132 ◽  
Author(s):  
Jonathan C. Edwards ◽  
Jeffrey D. Bodle
Keyword(s):  
Consensus Statement ◽  
Cellular Level ◽  
The Body ◽  
Professional Organizations ◽  
Sports Concussion ◽  
The Third ◽  
Orthopedic Surgeons ◽  
The Common ◽  
The Impact ◽  
The Brain

The Consensus Statement of the Third International Congress on Concussion in Sport in November 2008 defined concussion as a “complex pathophysiologic process affecting the brain, induced by traumatic biochemical forces.” Definitions of concussion vary slightly between various professional organizations of neurosurgeons, neurologists, and orthopedic surgeons, but all share the common characteristics of trauma affecting the head or body resulting in transient neurologic deficits or symptoms. Underlying the symptoms of concussion is a complex pathophysiologic process at the cellular level. While concussion is typically thought of as resulting from a direct impact to the head, a concussion can also be sustained as a result of an impact to the body causing the force of the impact to be transmitted to and absorbed by the brain.

scholarly journals Estimating directed connectivity from cortical recordings and reconstructed sources

2015 ◽  
Author(s):  
Margarita Papadopoulou ◽  
Karl J Friston ◽  
Daniele Marinazzo
Keyword(s):  
Cognitive Neuroscience ◽  
Brain Activity ◽  
Macaque Monkey ◽  
Sensor Data ◽  
Directed Transfer Function ◽  
Non Invasive ◽  
Scalp Eeg ◽  
Electrical Brain Activity ◽  
Source Level ◽  
The Brain

In cognitive neuroscience, electrical brain activity is most commonly recorded at the scalp. In order to infer the contributions and connectivity of underlying neuronal sources within the brain, it is necessary to reconstruct sensor data at the source level. Several approaches to this reconstruction have been developed, thereby solving the so-called implicit inverse problem (Michel et al. 2004). However, a unifying premise against which to validate these source reconstructions is seldom available. The dataset provided in this work, in which brain activity is simultaneously recorded on the scalp (non-invasively) by electroencephalography (EEG) and on the cortex (invasively) by electrocorticography (ECoG), can be of a great help in this direction. These multimodal recordings were obtained from a macaque monkey under in wakefulness and sedation. Our primary goal was to establish the connectivity architecture between two sources of interest (frontal and parietal), and to assess how their coupling changes over the conditions. We chose these sources because previous studies have shown that the connections between them are modified by anaesthesia (Boly et al. 2012). Our secondary goal was to evaluate the consistency of the connectivity results when analyzing sources recorded from invasive data (128 implanted ECoG sources) and source activity reconstructed from scalp recordings (19 EEG sensors) at the same locations as the ECoG sources. We conclude that the directed connectivity in the frequency domain between cortical sources reconstructed from scalp EEG is qualitatively similar to the connectivity inferred directly from cortical recordings, using both data-driven (directed transfer function; DTF) and biologically grounded (dynamic causal modelling; DCM) methods. Furthermore, the connectivity changes identified were consistent with previous findings (Boly et al. 2012). Our findings suggest that inferences about directed connectivity based upon non-invasive electrophysiological data have construct validity in relation to invasive recordings.

scholarly journals Spatiotemporal Analysis of Brain Activity During Understanding Honorific Expressions

2011 ◽  
Vol 15 (9) ◽  
pp. 1211-1220 ◽  
Author(s):  
Michio Sugeno ◽  
◽  
Takahiro Yamanoi ◽  
Keyword(s):  
Right Hemisphere ◽  
Brain Activity ◽  
Spatiotemporal Analysis ◽  
The Other ◽  
Dipole Source ◽  
Current Dipole ◽  
The Common ◽  
The Right ◽  
Spatiotemporal Processes ◽  
The Brain

This paper discusses brain activity during the understanding of sentences from the perspective of Systemic Functional Linguistics. We focus on ideational meaning (propositional meaning in an ordinary sense) and interpersonal meaning (as is typically seen in honorific expressions). The present study is an experimental exploration of the spatiotemporal pathways of neuronal activation. Japanese sentences containing and not containing honorific expressions are compared in electroencephalography experiments. In these experiments, the sentences without honorific expressions have ideationalmeaning, but those with honorific expressions have both ideational and interpersonal meanings. Through the use of the equivalent current dipole source localization method, the spatiotemporal processes of activation of the brain are analyzed. There is a single pathway during the understanding of the sentences without honorific expressions; this pathway is mainly observed in the left hemisphere. On the other hand, there are three pathways in the case of the sentences with honorific expressions, two of which are observed in the right hemisphere. The remaining pathway is the same as the aforementioned single pathway. This fact strongly suggests that the common pathway is concerned with processing ideational meaning. The other two pathways observed during understanding of the sentences with honorific expressions are considered to be related to processing interpersonal meaning.

scholarly journals Object novelty and value coding segregate across functionally connected brain networks

2019 ◽  
Author(s):  
Ali Ghazizadeh ◽  
MohammadAmin Fakharian ◽  
Arash Amini ◽  
Whitney Griggs ◽  
David A. Leopold ◽  
...  
Keyword(s):  
Brain Activity ◽  
Brain Networks ◽  
Temporal Cortex ◽  
Common Currency ◽  
Activation Dynamics ◽  
Fractal Patterns ◽  
The Common ◽  
Ventral Temporal Cortex ◽  
Value Coding ◽  
The Brain

AbstractNovel and valuable objects are motivationally attractive for animals including primates. However, little is known about how novelty and value processing is organized across the brain. We used fMRI in macaques to map brain activity to fractal patterns varying in either novelty or value dimensions in the context of functionally connected brain networks determined at rest. Results show unique combinations of novelty and value coding across the brain networks. Networks in the ventral temporal cortex and in the parietal cortex showed preferential coding of novelty and value dimensions, respectively, while a wider network composed of temporal and prefrontal areas (TP network), along with functionally connected portions of the striatum, amygdala, and claustrum, responded to both dimensions with similar activation dynamics. Our results support emergence of a common currency signal in the TP network that may underlie the common attitudes toward novel and valuable objects.

On the Possibilities of Magnetogasodynamic Lubrication

1967 ◽  
Vol 89 (3) ◽  
pp. 314-322
Author(s):  
V. N. Constantinescu
Keyword(s):  
Magnetic Field ◽  
Differential Equation ◽  
Electromagnetic Fields ◽  
Approximate Solutions ◽  
Pressure Differential ◽  
Electrical Field ◽  
Gas Bearings ◽  
External Electromagnetic Fields ◽  
Transversal Magnetic ◽  
Film Lubrication

The problem of gas film lubrication is considered, by assuming the existence of an electrical conductibility for the gas and that the motion is subjected to the influence of external electromagnetic fields. The MGD-lubrication equations are written under a general form. Several external electromagnetic conditions are considered, divided in two classes: (a) transversal magnetic field, and (b) tangential magnetic field combined with transversal electrical field. For each case the pressure differential equation is deduced and the possibilities of obtaining approximate solutions are briefly discussed, as well as the existence of some limiting solutions. Finally, the possibilities of improving the operation of both self-acting and externally pressurized gas bearings are pointed out.

scholarly journals Measurement of Brain Activity Rate Based on Electroensefalographical Signals on Smokers

2018 ◽  
Vol 3 (1) ◽  
pp. 15
Author(s):  
Herry Setiawan
Keyword(s):  
Brain Activity ◽  
Ion Current ◽  
Sampled Data ◽  
Voltage Difference ◽  
The Third ◽  
China And India ◽  
Level Information ◽  
Increased Activity ◽  
The Brain ◽  
Continue Smoking

Indonesia as a country with 255,182,144 people (Central Bureau of Statistics, 2015) with the number of smokers reached 46.16 percent in the third rank with the largest number of smokers in the world after China and India, there are some elements in cigarettes one of them is nicotine, it will be one of the addictive additives. It's why smokers want to continue smoking cigarettes on a regular basis. It bounds to the brain receptors and in other organs. Increased activity in the orbitofrontal area of the cortex occurs when a smoker wants a cigarette, while in the prefrontal cortex experiences an increase in activity when smokers smoke cigarettes. Increased activity in the area will produce electrically along the scalp that can be measured using Electroencephalography (EEG). The voltage difference of the ion current will give the addiction level information to the cigarette so it can be classified. Classification is done in 4 classes namely low dependence, Moderate dependence and high dependence. From the results of the study we found that the level of brain activity of the frontal cortex increased. 52% of the 40 sampled data showed the highest increase in activity by reaching 53.17% in the highly dependent addiction category.

scholarly journals Convection Enhanced Delivery of Topotecan for Gliomas: A Single-Center Experience

Pharmaceutics ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 39
Author(s):  
Pavan S. Upadhyayula ◽  
Eleonora F. Spinazzi ◽  
Michael G. Argenziano ◽  
Peter Canoll ◽  
Jeffrey N. Bruce
Keyword(s):  
Pressure Gradient ◽  
Malignant Glioma ◽  
Brain Parenchyma ◽  
Single Center ◽  
Convection Enhanced Delivery ◽  
Single Center Experience ◽  
Institutional Experience ◽  
The Common ◽  
The Brain ◽  
Physical Principles

A key limitation to glioma treatment involves the blood brain barrier (BBB). Convection enhanced delivery (CED) is a technique that uses a catheter placed directly into the brain parenchyma to infuse treatments using a pressure gradient. In this manuscript, we describe the physical principles behind CED along with the common pitfalls and methods for optimizing convection. Finally, we highlight our institutional experience using topotecan CED for the treatment of malignant glioma.

Advantages of Complementary Stereo Images as Viewed with the Low-Temperature Field-Emission SEM

1992 ◽  
Vol 50 (2) ◽  
pp. 1314-1315
Author(s):  
William P. Wergin ◽  
Eric F. Erbe
Keyword(s):  
Fold Increase ◽  
Horizontal Displacement ◽  
Three Dimensions ◽  
Stereo Image ◽  
Stereo Pair ◽  
Sem Micrograph ◽  
Left And Right ◽  
The Common ◽  
The Brain ◽  
Pair Analysis

The eye-brain complex allows those of us with normal vision to perceive and evaluate our surroundings in three-dimensions (3-D). The principle factor that makes this possible is parallax - the horizontal displacement of objects that results from the independent views that the left and right eyes detect and simultaneously transmit to the brain for superimposition. The common SEM micrograph is a 2-D representation of a 3-D specimen. Depriving the brain of the 3-D view can lead to erroneous conclusions about the relative sizes, positions and convergence of structures within a specimen. In addition, Walter has suggested that the stereo image contains information equivalent to a two-fold increase in magnification over that found in a 2-D image. Because of these factors, stereo pair analysis should be routinely employed when studying specimens.Imaging complementary faces of a fractured specimen is a second method by which the topography of a specimen can be more accurately evaluated.

Complexity Measures of Brain Electrophysiological Activity

2010 ◽  
Vol 24 (2) ◽  
pp. 131-135 ◽  
Author(s):  
Włodzimierz Klonowski ◽  
Pawel Stepien ◽  
Robert Stepien
Keyword(s):  
Brain Activity ◽  
Deterministic Chaos ◽  
Epileptic Seizures ◽  
Eeg Signal ◽  
Eeg Signals ◽  
Complexity Measures ◽  
Electrophysiological Activity ◽  
Signal Complexity ◽  
Physiological Sleep ◽  
The Brain

Over 20 years ago, Watt and Hameroff (1987 ) suggested that consciousness may be described as a manifestation of deterministic chaos in the brain/mind. To analyze EEG-signal complexity, we used Higuchi’s fractal dimension in time domain and symbolic analysis methods. Our results of analysis of EEG-signals under anesthesia, during physiological sleep, and during epileptic seizures lead to a conclusion similar to that of Watt and Hameroff: Brain activity, measured by complexity of the EEG-signal, diminishes (becomes less chaotic) when consciousness is being “switched off”. So, consciousness may be described as a manifestation of deterministic chaos in the brain/mind.

Relation Between Level of Prefrontal Activity and Subject's Performance

1999 ◽  
Vol 13 (2) ◽  
pp. 117-125 ◽  
Author(s):  
Laurence Casini ◽  
Françoise Macar ◽  
Marie-Hélène Giard
Keyword(s):  
Brain Activity ◽  
Sensory Information ◽  
Practice Phase ◽  
Trained Subjects ◽  
Anagram Task ◽  
Economic Information ◽  
Long Duration ◽  
Level Of Activity ◽  
The Brain ◽  
Processing Mechanism

Abstract The experiment reported here was aimed at determining whether the level of brain activity can be related to performance in trained subjects. Two tasks were compared: a temporal and a linguistic task. An array of four letters appeared on a screen. In the temporal task, subjects had to decide whether the letters remained on the screen for a short or a long duration as learned in a practice phase. In the linguistic task, they had to determine whether the four letters could form a word or not (anagram task). These tasks allowed us to compare the level of brain activity obtained in correct and incorrect responses. The current density measures recorded over prefrontal areas showed a relationship between the performance and the level of activity in the temporal task only. The level of activity obtained with correct responses was lower than that obtained with incorrect responses. This suggests that a good temporal performance could be the result of an efficacious, but economic, information-processing mechanism in the brain. In addition, the absence of this relation in the anagram task results in the question of whether this relation is specific to the processing of sensory information only.

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