The document provides an overview of MEG and brain signals. It discusses:
1) How MEG measures the magnetic fields generated by intracellular and extracellular current flows in the brain.
2) The origin and properties of the neuroelectric/neuromagnetic signal, including that a dipole moment is generated from synchronized activity of neurons.
3) How MEG detects mainly tangential sources on the cortical surface rather than radial sources.
4) Common oscillatory patterns measured with MEG like gamma, beta, alpha, and theta oscillations and how their power changes with cognitive tasks.
This document discusses neural coding and how neurons encode information during cognitive tasks. It summarizes research using single-unit neural recordings in rats performing a directional control task. Three key findings are presented:
1) Neural firing rates in areas like PM and M1 encoded information about trial outcomes and the rat's learning progress over multiple sessions.
2) Precise spike timing provided information about the rat's cognitive state, with more synchronized activity observed early in learning.
3) Network modeling revealed changes in functional connectivity between neurons associated with synaptic plasticity, with more optimized patterns emerging as the rat became proficient at the task.
Introduction to Modern Methods and Tools for Biologically Plausible Modelling...SSA KPI
1. The document discusses modern methods and tools for biologically plausible modeling of neural structures in the brain.
2. It reviews several neuron and synapse models of varying complexity, from detailed models to more simplified integrate-and-fire models.
3. Learning and memory mechanisms are discussed from the single neuron level to the network level, including models of spike-timing dependent plasticity and the role of local calcium dynamics in synaptic plasticity. Open issues in learning and memory are also noted.
MagnetoenCephaloGraphy (MEG) is a technique for mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain, using very sensitive magnetometers.
Magnetoencephalography (meg) and diffusion tensor imagingAdonis Sfera, MD
The document discusses using magnetoencephalography (MEG) and diffusion tensor imaging (DTI) to better diagnose mild traumatic brain injury (mTBI) and post-traumatic stress disorder (PTSD). Conventional imaging like CT and MRI often miss injuries from mTBI and find nothing abnormal for PTSD. MEG can detect abnormal low-frequency brain signals from injured areas in mTBI patients. DTI can find reduced anisotropy in white matter tracts, providing evidence of axonal injuries linked to areas generating MEG signals. Combining MEG and DTI findings provides stronger evidence of neuronal injury in mTBI than conventional imaging alone. MEG may also detect hyperactivated brain networks involved in PTSD
The document provides an overview of magnetic resonance imaging (MRI), including how it works, the types of images it can produce, and its applications in various parts of the body. It explains that MRI uses strong magnetic fields and radio waves to align hydrogen protons in the body and produce signals used to form images. Key applications mentioned include neuroimaging, musculoskeletal imaging, and evaluating diseases of the abdomen, blood vessels, heart, breast and fetus.
A short description of the brain scanning method: electroencephalogram. In addition o the basic method, the slideshow also briefly describes the techniques strengths and weaknesses compared to other brain scanning techniques.
fMRI technology uses the nuclear magnetic resonance (NMR) phenomenon to form images of neural activity in the brain. It relies on the different magnetic properties of oxygenated and deoxygenated hemoglobin. When neurons are active in a region of the brain, blood flow to that region increases, altering the ratio of oxygenated to deoxygenated hemoglobin and causing a change in the MRI signal. Spatial encoding techniques allow fMRI to locate these signal changes within the brain and form a 3D image showing patterns of neural activity.
This document discusses neural coding and how neurons encode information during cognitive tasks. It summarizes research using single-unit neural recordings in rats performing a directional control task. Three key findings are presented:
1) Neural firing rates in areas like PM and M1 encoded information about trial outcomes and the rat's learning progress over multiple sessions.
2) Precise spike timing provided information about the rat's cognitive state, with more synchronized activity observed early in learning.
3) Network modeling revealed changes in functional connectivity between neurons associated with synaptic plasticity, with more optimized patterns emerging as the rat became proficient at the task.
Introduction to Modern Methods and Tools for Biologically Plausible Modelling...SSA KPI
1. The document discusses modern methods and tools for biologically plausible modeling of neural structures in the brain.
2. It reviews several neuron and synapse models of varying complexity, from detailed models to more simplified integrate-and-fire models.
3. Learning and memory mechanisms are discussed from the single neuron level to the network level, including models of spike-timing dependent plasticity and the role of local calcium dynamics in synaptic plasticity. Open issues in learning and memory are also noted.
MagnetoenCephaloGraphy (MEG) is a technique for mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain, using very sensitive magnetometers.
Magnetoencephalography (meg) and diffusion tensor imagingAdonis Sfera, MD
The document discusses using magnetoencephalography (MEG) and diffusion tensor imaging (DTI) to better diagnose mild traumatic brain injury (mTBI) and post-traumatic stress disorder (PTSD). Conventional imaging like CT and MRI often miss injuries from mTBI and find nothing abnormal for PTSD. MEG can detect abnormal low-frequency brain signals from injured areas in mTBI patients. DTI can find reduced anisotropy in white matter tracts, providing evidence of axonal injuries linked to areas generating MEG signals. Combining MEG and DTI findings provides stronger evidence of neuronal injury in mTBI than conventional imaging alone. MEG may also detect hyperactivated brain networks involved in PTSD
The document provides an overview of magnetic resonance imaging (MRI), including how it works, the types of images it can produce, and its applications in various parts of the body. It explains that MRI uses strong magnetic fields and radio waves to align hydrogen protons in the body and produce signals used to form images. Key applications mentioned include neuroimaging, musculoskeletal imaging, and evaluating diseases of the abdomen, blood vessels, heart, breast and fetus.
A short description of the brain scanning method: electroencephalogram. In addition o the basic method, the slideshow also briefly describes the techniques strengths and weaknesses compared to other brain scanning techniques.
fMRI technology uses the nuclear magnetic resonance (NMR) phenomenon to form images of neural activity in the brain. It relies on the different magnetic properties of oxygenated and deoxygenated hemoglobin. When neurons are active in a region of the brain, blood flow to that region increases, altering the ratio of oxygenated to deoxygenated hemoglobin and causing a change in the MRI signal. Spatial encoding techniques allow fMRI to locate these signal changes within the brain and form a 3D image showing patterns of neural activity.
This document summarizes key aspects of ultrasound therapy. It discusses ultrasound transmission and propagation through tissues, the components of an ultrasound generator including the transducer and piezoelectric effect, physiological effects including thermal and non-thermal effects, techniques for application, indications and contraindications.
MEG measures magnetic fields produced by electrical activity in the brain. It provides high spatial resolution to localize brain regions activated during specific cognitive tasks and can help localize epileptic seizures. While MEG was first developed in the 1970s, advances over decades now allow it to map brain rhythms, language processing, connectivity between regions, and development from prenatal periods to learning. Key applications include epilepsy evaluation, mapping functional areas near brain tumors to guide surgery, and monitoring stroke recovery and chronic pain.
The document summarizes testing of the autonomic nervous system, including the sympathetic and parasympathetic divisions. It describes several tests used to evaluate autonomic function clinically, including heart rate variability tests like deep breathing and Valsalva maneuver, as well as sympathetic skin response testing. Preparation of patients and protocols for each test are provided. The tests can help diagnose autonomic dysfunction and define its severity and distribution.
The document describes four autonomic function tests related to the cardiovascular system: 1) Heart rate variation during respiration measures vagal control of heart rate, 2) Heart rate variation during postural change assesses parasympathetic response, 3) The Valsalva maneuver evaluates sympathetic and parasympathetic function by measuring blood pressure and heart rate responses to forced exhalation, 4) The cold pressor test increases blood pressure by submerging a hand in ice water to stimulate the sympathetic nervous system. These tests are used to evaluate autonomic nervous system integrity.
This document discusses how analytics can help drive business performance in the semiconductor manufacturing industry. It provides an overview of the industry, key metrics like wafer size, node size, yield, utilization, and OEE. It also discusses data sources in semiconductor manufacturing and losses that occur. Analytics can help identify issues, optimize processes, and improve efficiency, yield, and decision making to help manufacturers address challenges and scale production.
The effect of conditional probability of chord progression in Western music c...Seung-Goo Kim
The effect of conditional probability of chord progression in Western music corpus on brain response: an MEG study. “Joint symposium in celebration of the 20th anniversary of Korea-German Society for Music” (organized by Dr. Suk Won Yi). Seoul, South Korea. Sep 11, 2010.
This document provides information on setting up an oxygen gas cylinder filling station, including an estimated cost and project report. It notes that manufacturers of oxygen cylinder filling plants can provide engineering support until the machine is performing well and operators are properly trained, so not to waste time in setting up the station.
Reducing Helium Use for GMAW on Nickel Based Alloys - QuickViewMATHESON
This document discusses reducing the use of helium in gas metal arc welding (GMAW) applications on nickel-based alloys. It notes that helium is a non-renewable resource with an unpredictable supply and fluctuating prices. While helium creates a hot arc useful for thicker materials, it also has disadvantages like inconsistent welds and heat-related damage. The document promotes using Matheson Select shielding gas mixtures that can reduce helium use by up to 90% while improving weld quality and expanding the usable voltage range. It presents the mixture as a single setup solution for short circuit, spray arc, and pulsed spray welding of stainless steels, Inconel, Hastelloy, and Mon
Test your Electrical Equipment with Thermographic Imagingleedyweb
Thermographic Imaging, also known as Infrared Imaging is a method of detecting thermal levels in electrical systems. Leedy Electric West specializes is using these scans to evaluate your electrical system for safety and early detection of electrical trouble spots. Contact Leedy Electric West at (813)630-2698 for more information. Thermographic Imaging for Central Florida
Hydrogen is the most abundant element in the universe and is found in stars and gas giant planets. It is the lightest element and is non-toxic, odorless and highly flammable. English scientist Henry Cavendish discovered hydrogen in 1766 by running an experiment using zinc and hydrochloric acid. The name hydrogen comes from Greek meaning "water-former" as burning hydrogen produces water. Today, hydrogen is used to make ammonia, refine metals, and power rockets. Most hydrogen on Earth is found in water, though some exists underground. In stars, hydrogen fuses to form helium, releasing heat and energy.
This document summarizes the history, physical properties, and applications of titanium and helium. It discusses how titanium was discovered in 1791 and isolated in 1910. It is a strong, lightweight metal that is resistant to corrosion. Its major uses are in aerospace alloys and implants due to its strength and biocompatibility. Helium was first detected in the sun in 1868 and isolated on Earth in 1895. It is odorless and inert. Its main uses are in MRI machines for cooling magnets and as a shield gas for welding.
This document discusses the history and types of lasers. It describes how lasers work using the principles of stimulated and spontaneous emission to produce population inversion and pumping. The main types of lasers covered are solid state lasers like Nd:YAG and ruby, gas lasers like He-Ne and CO2, liquid/dye lasers using materials like coumarin dye, and semiconductor lasers made from compounds like GaAs. Applications discussed include industrial uses in welding, cutting, and heat treatment, as well as medical, holography, construction, defense, and laser light shows.
1. The document discusses developing computational and statistical models to better understand how the brain separates and identifies different sound sources from mixtures of sounds entering the ears.
2. It explores using these models to simulate neural activity along the auditory pathway and improve artificial recognition of sounds from neuronal data, with the goal of advancing hearing aids and understanding normal hearing.
3. Developing these models and statistical techniques requires an interdisciplinary approach combining neuroscience, mathematics, and data science to solve the complex problem of how the brain processes sound.
In this study,
We propose a EEG analysis model using a nonlinear oscillator with one degree of freedom.
It doesn’t have a random term.
our study method identifies six model parameters experimentally.
Here is the detail: https://kenyu-life.com/2018/11/03/modeling_of_eeg/
Created by Kenyu Uehara
Introduction to Modern Methods and Tools for Biologically Plausible Modelling...SSA KPI
This document provides an overview of modern methods and tools for biologically plausible modeling of neural structures in the brain. It discusses modeling at different levels, from the system level looking at the brain as a whole, down to the subcellular and molecular levels examining individual neurons and ion channels. At each level, it outlines key research methods used to study the brain experimentally and different modeling approaches, including population and dynamical models, formal neural networks, and detailed single-cell models. The document also reviews seminal work in neuroscience like Hodgkin and Huxley's equations for modeling ion channel dynamics and spike generation in neurons.
This document summarizes research conducted at the Sir Peter Mansfield Magnetic Resonance Centre using multimodal neuroimaging techniques including fMRI, MEG, and structural MRI. It discusses findings such as increasing BOLD contrast and functional sensitivity at higher magnetic field strengths for fMRI. It also shows retinotopic mapping results using MEG and comparisons of neural responses measured with fMRI and MEG for different visual stimuli. In general, the document highlights the complementary information provided by multimodal neuroimaging approaches for studying brain structure and function.
This document describes a study that tested the effectiveness of using Signa gel with tripolar concentric ring electrodes (TCREs) to record electroencephalography (EEG) signals from the brain. TCREs are a type of electrode that can help reduce noise in EEG recordings compared to conventional disc electrodes. The study found that 10 mm diameter TCREs attached with Signa gel were able to clearly detect alpha wave brain activity, but smaller 6 mm and 4 mm TCREs were less consistent, possibly due to noisy connections to the recording interface. The results suggest Signa gel is suitable for impedance matching when using multiple TCREs to obtain high-resolution EEG recordings.
This document describes constructing a Monte Carlo model of a multi-population neural network to compare with mean field and population density methods. It summarizes modeling neural activity across populations with different physiological characteristics. Simulation results show the Monte Carlo method can accurately model population interactions and parameter variations, making it suitable for testing population density methods. The document concludes additional physiological variables should be included in future simulations.
The document discusses electrophysiology techniques used to study the electrical activity of neurons and other excitable cells. It begins by explaining that electrophysiology allows measurement of ionic currents across cell membranes and helps understand how cells and tissues function. Different techniques are then described, including intracellular recordings, patch clamp recordings, and extracellular recordings. The document outlines the historical development of the field and covers topics like resting membrane potentials, action potentials, ion channels, and how neurons encode and transmit information.
Ultrasound was used to image electric field induced changes in biological tissues and phantoms. Experiments measured changes in ultrasound echo amplitude and signal properties like mean and noise while applying electric fields of varying amplitude and frequency. Results showed the electric field caused measurable changes in ultrasound echo properties from both tissue and phantom samples, indicating ultrasound can detect electric field distributions and their effects on materials.
Envelope coding in the cochlear nucleus: a data mining approachAlbanLevy
This document analyzes spike train data from the cochlear nucleus using data mining techniques to better understand envelope coding. It finds that modern machine learning methods can extract modulation frequency from spike patterns without strong assumptions. Classification accuracy varies by neuron type and is highest for onset units, consistent with their role in encoding periodicity. Optimal timescales are sub-millisecond, and different preprocessing methods like interspike interval features or spike timing yield similar results. The analysis characterizes neurons' modulation transfer functions and suggests they act as low-pass filters for envelope information.
This document summarizes key aspects of ultrasound therapy. It discusses ultrasound transmission and propagation through tissues, the components of an ultrasound generator including the transducer and piezoelectric effect, physiological effects including thermal and non-thermal effects, techniques for application, indications and contraindications.
MEG measures magnetic fields produced by electrical activity in the brain. It provides high spatial resolution to localize brain regions activated during specific cognitive tasks and can help localize epileptic seizures. While MEG was first developed in the 1970s, advances over decades now allow it to map brain rhythms, language processing, connectivity between regions, and development from prenatal periods to learning. Key applications include epilepsy evaluation, mapping functional areas near brain tumors to guide surgery, and monitoring stroke recovery and chronic pain.
The document summarizes testing of the autonomic nervous system, including the sympathetic and parasympathetic divisions. It describes several tests used to evaluate autonomic function clinically, including heart rate variability tests like deep breathing and Valsalva maneuver, as well as sympathetic skin response testing. Preparation of patients and protocols for each test are provided. The tests can help diagnose autonomic dysfunction and define its severity and distribution.
The document describes four autonomic function tests related to the cardiovascular system: 1) Heart rate variation during respiration measures vagal control of heart rate, 2) Heart rate variation during postural change assesses parasympathetic response, 3) The Valsalva maneuver evaluates sympathetic and parasympathetic function by measuring blood pressure and heart rate responses to forced exhalation, 4) The cold pressor test increases blood pressure by submerging a hand in ice water to stimulate the sympathetic nervous system. These tests are used to evaluate autonomic nervous system integrity.
This document discusses how analytics can help drive business performance in the semiconductor manufacturing industry. It provides an overview of the industry, key metrics like wafer size, node size, yield, utilization, and OEE. It also discusses data sources in semiconductor manufacturing and losses that occur. Analytics can help identify issues, optimize processes, and improve efficiency, yield, and decision making to help manufacturers address challenges and scale production.
The effect of conditional probability of chord progression in Western music c...Seung-Goo Kim
The effect of conditional probability of chord progression in Western music corpus on brain response: an MEG study. “Joint symposium in celebration of the 20th anniversary of Korea-German Society for Music” (organized by Dr. Suk Won Yi). Seoul, South Korea. Sep 11, 2010.
This document provides information on setting up an oxygen gas cylinder filling station, including an estimated cost and project report. It notes that manufacturers of oxygen cylinder filling plants can provide engineering support until the machine is performing well and operators are properly trained, so not to waste time in setting up the station.
Reducing Helium Use for GMAW on Nickel Based Alloys - QuickViewMATHESON
This document discusses reducing the use of helium in gas metal arc welding (GMAW) applications on nickel-based alloys. It notes that helium is a non-renewable resource with an unpredictable supply and fluctuating prices. While helium creates a hot arc useful for thicker materials, it also has disadvantages like inconsistent welds and heat-related damage. The document promotes using Matheson Select shielding gas mixtures that can reduce helium use by up to 90% while improving weld quality and expanding the usable voltage range. It presents the mixture as a single setup solution for short circuit, spray arc, and pulsed spray welding of stainless steels, Inconel, Hastelloy, and Mon
Test your Electrical Equipment with Thermographic Imagingleedyweb
Thermographic Imaging, also known as Infrared Imaging is a method of detecting thermal levels in electrical systems. Leedy Electric West specializes is using these scans to evaluate your electrical system for safety and early detection of electrical trouble spots. Contact Leedy Electric West at (813)630-2698 for more information. Thermographic Imaging for Central Florida
Hydrogen is the most abundant element in the universe and is found in stars and gas giant planets. It is the lightest element and is non-toxic, odorless and highly flammable. English scientist Henry Cavendish discovered hydrogen in 1766 by running an experiment using zinc and hydrochloric acid. The name hydrogen comes from Greek meaning "water-former" as burning hydrogen produces water. Today, hydrogen is used to make ammonia, refine metals, and power rockets. Most hydrogen on Earth is found in water, though some exists underground. In stars, hydrogen fuses to form helium, releasing heat and energy.
This document summarizes the history, physical properties, and applications of titanium and helium. It discusses how titanium was discovered in 1791 and isolated in 1910. It is a strong, lightweight metal that is resistant to corrosion. Its major uses are in aerospace alloys and implants due to its strength and biocompatibility. Helium was first detected in the sun in 1868 and isolated on Earth in 1895. It is odorless and inert. Its main uses are in MRI machines for cooling magnets and as a shield gas for welding.
This document discusses the history and types of lasers. It describes how lasers work using the principles of stimulated and spontaneous emission to produce population inversion and pumping. The main types of lasers covered are solid state lasers like Nd:YAG and ruby, gas lasers like He-Ne and CO2, liquid/dye lasers using materials like coumarin dye, and semiconductor lasers made from compounds like GaAs. Applications discussed include industrial uses in welding, cutting, and heat treatment, as well as medical, holography, construction, defense, and laser light shows.
1. The document discusses developing computational and statistical models to better understand how the brain separates and identifies different sound sources from mixtures of sounds entering the ears.
2. It explores using these models to simulate neural activity along the auditory pathway and improve artificial recognition of sounds from neuronal data, with the goal of advancing hearing aids and understanding normal hearing.
3. Developing these models and statistical techniques requires an interdisciplinary approach combining neuroscience, mathematics, and data science to solve the complex problem of how the brain processes sound.
In this study,
We propose a EEG analysis model using a nonlinear oscillator with one degree of freedom.
It doesn’t have a random term.
our study method identifies six model parameters experimentally.
Here is the detail: https://kenyu-life.com/2018/11/03/modeling_of_eeg/
Created by Kenyu Uehara
Introduction to Modern Methods and Tools for Biologically Plausible Modelling...SSA KPI
This document provides an overview of modern methods and tools for biologically plausible modeling of neural structures in the brain. It discusses modeling at different levels, from the system level looking at the brain as a whole, down to the subcellular and molecular levels examining individual neurons and ion channels. At each level, it outlines key research methods used to study the brain experimentally and different modeling approaches, including population and dynamical models, formal neural networks, and detailed single-cell models. The document also reviews seminal work in neuroscience like Hodgkin and Huxley's equations for modeling ion channel dynamics and spike generation in neurons.
This document summarizes research conducted at the Sir Peter Mansfield Magnetic Resonance Centre using multimodal neuroimaging techniques including fMRI, MEG, and structural MRI. It discusses findings such as increasing BOLD contrast and functional sensitivity at higher magnetic field strengths for fMRI. It also shows retinotopic mapping results using MEG and comparisons of neural responses measured with fMRI and MEG for different visual stimuli. In general, the document highlights the complementary information provided by multimodal neuroimaging approaches for studying brain structure and function.
This document describes a study that tested the effectiveness of using Signa gel with tripolar concentric ring electrodes (TCREs) to record electroencephalography (EEG) signals from the brain. TCREs are a type of electrode that can help reduce noise in EEG recordings compared to conventional disc electrodes. The study found that 10 mm diameter TCREs attached with Signa gel were able to clearly detect alpha wave brain activity, but smaller 6 mm and 4 mm TCREs were less consistent, possibly due to noisy connections to the recording interface. The results suggest Signa gel is suitable for impedance matching when using multiple TCREs to obtain high-resolution EEG recordings.
This document describes constructing a Monte Carlo model of a multi-population neural network to compare with mean field and population density methods. It summarizes modeling neural activity across populations with different physiological characteristics. Simulation results show the Monte Carlo method can accurately model population interactions and parameter variations, making it suitable for testing population density methods. The document concludes additional physiological variables should be included in future simulations.
The document discusses electrophysiology techniques used to study the electrical activity of neurons and other excitable cells. It begins by explaining that electrophysiology allows measurement of ionic currents across cell membranes and helps understand how cells and tissues function. Different techniques are then described, including intracellular recordings, patch clamp recordings, and extracellular recordings. The document outlines the historical development of the field and covers topics like resting membrane potentials, action potentials, ion channels, and how neurons encode and transmit information.
Ultrasound was used to image electric field induced changes in biological tissues and phantoms. Experiments measured changes in ultrasound echo amplitude and signal properties like mean and noise while applying electric fields of varying amplitude and frequency. Results showed the electric field caused measurable changes in ultrasound echo properties from both tissue and phantom samples, indicating ultrasound can detect electric field distributions and their effects on materials.
Envelope coding in the cochlear nucleus: a data mining approachAlbanLevy
This document analyzes spike train data from the cochlear nucleus using data mining techniques to better understand envelope coding. It finds that modern machine learning methods can extract modulation frequency from spike patterns without strong assumptions. Classification accuracy varies by neuron type and is highest for onset units, consistent with their role in encoding periodicity. Optimal timescales are sub-millisecond, and different preprocessing methods like interspike interval features or spike timing yield similar results. The analysis characterizes neurons' modulation transfer functions and suggests they act as low-pass filters for envelope information.
Introduction to modern methods and tools for biologically plausible modeling ...SSA KPI
AACIMP 2010 Summer School lecture by Ruben Tikidji-Hamburyan. "Physics, Chemistry and Living Systems" stream. "Introduction to Modern Methods and Tools for Biologically Plausible Modeling of Neurons and Neural Networks" course. Part 1.
More info at http://summerschool.ssa.org.ua
1. The document describes experiments and models of visual cortex neurons and their responses to visual stimuli.
2. A 2-dimensional continuum model of visual cortex is presented, with excitatory and inhibitory neuron populations in different layers and types of synapses between them.
3. The model is able to simulate responses of neurons to changes in orientation of visual stimuli and capture effects of adaptation and stimulus contrast. Comparisons are made to experimental data.
The document provides information on electroencephalography (EEG) and magnetoencephalography (MEG). It discusses the history of EEG, how the signals are recorded, various montages used, neural basis of the signals, analysis methods for EEG including evoked potentials and artifacts. MEG is described as detecting the magnetic fields generated by electrical activity in the brain using SQUIDs, and its increased sensitivity to activity in sulcal walls compared to EEG. Key differences between the two methods are the orientation of measured fields relative to current flow in neurons.
MSEE Defense: Digital Processor to Monitor the Muscular Energy Drop in Surfac...rff001
This document describes a digital processor to monitor muscular energy drop in surface electromyograms (EMGs). The processor aims to monitor fatigue in muscles undergoing neuromuscular electrical stimulation (NMES) rehabilitation. It analyzes EMG signals to extract spectral parameters that quantify fatigue, like root mean square, average rectified value, and mean and medium frequencies. These parameters are used in a proposed NMES control system to monitor energy decrease and prevent total muscle fatigue. A digital processing unit was developed using MATLAB to validate the technique.
This experiment tested the effect of strobing lights at different frequencies (2 Hz, 10 Hz, and 20 Hz) on visual reaction time and brainwave activity, as measured by EEG. Twelve subjects performed a visual reaction time test in ambient light, dark, and dark conditions with each strobe frequency. Their average reaction times and alpha wave RMS values were calculated for each condition. Results found that 10 Hz strobing tended to decrease reaction time compared to dark conditions, while responses to 2 Hz and 20 Hz strobing were mixed, with some subjects faster and some slower. EEG activity spiked larger in response to flashes compared to dark conditions. Improvements could include better electrode contact and consistent lighting across subjects.
EEG records electric potentials from the brain using electrodes on the scalp. It has high temporal resolution but low spatial resolution. MEG records magnetic fields generated by neural activity using SQUID magnetometers and has similar properties as EEG. ERPs are extracted from EEG/MEG data by averaging time-locked responses to events and are characterized by polarity and latency. EEG/MEG/ERPs are useful for studying cognitive processes and clinical applications when high temporal resolution is required.
Experimental Neutrino Physics Concepts in Nutshell Son Cao
This document provides an overview of the key steps involved in designing and conducting neutrino oscillation experiments. It discusses how experimental neutrino physicists formulate hypotheses about neutrino oscillations, design experiments to test these hypotheses, build and operate detectors to collect data, and make statements based on the observed data. Specific examples from T2K and NOvA are used to illustrate how these experiments addressed challenges like creating neutrino beams, choosing detector locations, and identifying electron neutrinos emerging from muon neutrino beams. The document aims to provide theoretical physics students a practical guide for thinking about neutrino experiments.
1. Population models describe the activity of groups of similar neurons receiving common input. They include firing-rate models and the probability density approach.
2. The refractory density approach models populations using a hazard function that describes the probability of individual neurons firing. It can accurately model both stationary and non-stationary activity.
3. Conductance-based refractory density and firing-rate models can simulate the responses of coupled neuronal populations to different input patterns and reproduce experimental observations of population-level activity.
1. MEG introduction
Brain Signals
MEG seminar
Oct 06 2011
Bernhard Ross
Rotman Research Institute
Department of Medical Biophysics 400 fT
University of Toronto
1.0 s
2. Brain signals recorded with EEG and MEG
Understanding the neural mechanism underlying the EEG/MEG
signal and knowing about the possibilities and limitations of the
methods has a large impact on design and performance of a
successful study.
3. The origin of the neuroelectric / neuromagnetic signal
4. The origin of the neuroelectric / neuromagnetic signal
5. The origin of the neuroelectric / neuromagnetic signal
Ramon y Cajal
6. The origin of the neuroelectric / neuromagnetic signal
7. Intra-cellular current flow
Transmembrane current flow
Intracellular current flow
Extracellular current flow
The intracellular current
flow generates an
external
electromagnetic field
8. Source activity: The dipole moment
T
¡e
¡ e
dl
I
c
Dipolemoment:
q = I · dl
(Am, nAm)
9. Source activity: The dipole moment
Dipole moment of a
T single neuron:
¡e 0.2 . . . 0.5 pAm
¡ e
dl e.g.:
I I=0.5nA, dl=1mm
c
Dipolemoment:
q = I · dl
(Am, nAm)
10. Source activity: The dipole moment
Dipole moment of a
T single neuron:
¡e 0.2 . . . 0.5 pAm
¡ e
dl e.g.:
I ¡e I=0.5nA, dl=1mm
¡ e
n·I
c
Dipolemoment:
q = I · dl
(Am, nAm) Dipolemoment:
q = n · I · dl
11. Source activity: The dipole moment
Dipole moment of a
T single neuron:
¡e 0.2 . . . 0.5 pAm
¡ e
dl e.g.:
I ¡e I=0.5nA, dl=1mm
¡ e
n·I MEG/EEG evoked
c response:
1 . . . 100 nAm
n=2000 . . . 500,000
synchronously active
neurons
Dipolemoment:
q = I · dl
(Am, nAm) Dipolemoment:
q = n · I · dl
12. Source of the MEG: – Anatomical organization in columnar structures
FROM: Hutsler and Galuske Trends in Neuroscience, 2003, 26:429-435
Neurons in the neocortex are organized in a hierarchy of micro-
and macro-columns.
17. Not all sources appear equally in the MEG
A dipole tangential to the skull produces a
strong magnetic field outside the head.
A radial source may be missed in the MEG
31. Why do we have positive and negative response components?
FROM: Niedermeyer and Lopes da Silva
Two factors decide about the polarity of the response:
1. The nature of synaptic connection: excitatory or inhibitory.
2. The location of synaptic contact: apical or basal.
Generally, subsequent waves are generated in different micro circuits.
32. Event related responses
Early responses are strictly time-locked to the stimulus (exogenous
components)
Later responses are time-locked to internal processing (endogenous
components)
trade off around 250 ms (?)
33. The first human MEG recording
David Cohen, Jim Zimmerman, MIT, 1971
single channel SQUID sensor
34. The first human MEG recording
David Cohen, Jim Zimmerman, MIT, 1971
single channel SQUID sensor
35. The first human MEG recording
David Cohen, Jim Zimmerman, MIT, 1971
single channel SQUID sensor
36. The first human MEG recording
David Cohen, Jim Zimmerman, MIT, 1971
single channel SQUID sensor
37. The first human MEG recording
David Cohen, Jim Zimmerman, MIT, 1971
single channel SQUID sensor
Hans Berger, 1929
38. The first human MEG recording
David Cohen, Jim Zimmerman, MIT, 1971
single channel SQUID sensor
39. Beta oscillations 15-30 Hz
Beta oscillations have been first observed in the motor system.
Beta increased during preparation for a movement.
Beta decreased at initiation of the movement.
and beta increased again at the end of the movement
Beta oscillations are involved in sensorimotor integration
Modulation of beta oscillation have been found in the auditory and
visual system.
40. Gamma oscillations 30-80 Hz
Gamma oscillation have been first observed as a short burst after
stimulus onset in the visual modality - also with auditory and
somatosensory stimulation.
There is a large interest in gamma oscillation because of a strong
theoretical framework related to feature binding, attention,
consciousness ...
Gamma oscillations always increase in the active state
42. early gamma oscillation are
time (phase) locked to the
stimulus and can be detected
in the averaged sgnal
Endogenous gamma
oscillations are less strictly
time (phase) locked to the
stimulus. The signal is
canceled out in the average.
Instead we can analyze the
event related changes in the
magnitude of oscillation.
43. Event related changes in oscillatory activity
120
2
γ2 100
0
80 Time-frequency
-2
analysis of the MEG
2
γ1 50 signal
Signal Power Change (dB)
40 0
Change in signal
Frequency (Hz)
30 -2 strength relative to an
28
2 inactive pre-stimulus
β 24
interval
20 0
16 -2 The signal changes
14 are often termed
3
α 12 ’Event related
0
10 synchronisation (ERS)’
8 -3 and ’Event related
8 12 desynchronisation
7 6
6 (ERD)’
0
θ 5
4 -6
3 -12
-0.5 0 0.5 1 1.5 2
Time (s)
44. Synchrony between gamma oscillations
Source Strength (nAm) 100
50
0
-50
-100
-0.4 -0.2 0 0.2 0.4 0.6 0.8 1
Time (s)
45. Synchrony between gamma oscillations
Source Strength (nAm) 100
50
0
-50
-100
-0.4 -0.2 0 0.2 0.4 0.6 0.8 1
Time (s)
46. Synchrony between gamma oscillations
20
Source Strength (nAm)
10
0
-10
-20
-0.4 -0.2 0 0.2 0.4 0.6 0.8 1
Time (s)
47. Synchrony between gamma oscillations
10
Source Strength (nAm)
0
-10
-20
-30
-0.4 -0.2 0 0.2 0.4 0.6 0.8 1
Time (s)
48. Synchrony between gamma oscillations
20
Source Strength (nAm)
10
0
-10
-20
-0.4 -0.2 0 0.2 0.4 0.6 0.8 1
Time (s)
51. Analysis of oscillatory activity
Phase locked responses (averaging, phase statistics)
Event related changes in signal magnitude (ERS, ERD)
Coherence between sensor signals and between source signals
Event related changes in coherence
Analysis of coupling between frequency bands (gamma - theta)
Steady-state approaches