Methods: MEG 1

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  • Created by: CanveySam
  • Created on: 06-05-15 12:08
What does MEG stand for?
Magnetoencephalography
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What does MEG measure?
magnetic fields, generated by the brain
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How does MEG differ from EEG?
1) can be measured at a single point 2) no reference point needed 3) no electrical circuit
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What are the implications of an MEG not involving electrical circuits?
Signal unimpeded by skull, signal less spread out, therefore better spatial resolution
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What neurons and potentials are involved?
PYRAMIDAL and POSTYNAPTIC potentials (last 20ms)
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What is the right hand rule?
no - Radial dipole; yes - Tangential dipole
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2 methods of noise cancellation?
1) Sensor design 2) Shielded room (Faraday cage)
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What does SQUID stand for?
Superconducting Quantum Interference Device - high tech and expensive
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3 other noise removal methods?
1) filtering e.g. low pass, high pass, 50Hz 2) reference subtracted from SQUID 3) averaging e.g. over 100,000 trials
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How many MEG sensors are used?
Up to 275
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Compare position of sensors between MEG and EEG
EEG - stuck but head movements can cause transient artefacts. MEG - loose over so if the head moves the position changes
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what does ERF stand for?
Event Related Field
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what is used to transform data to a time frequency histogram?
time-frequency decomposition
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Why use MEG for mismatch negativity?
Faster, sensitive to source only, many sensors
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Compare MEG/EEG for dipoles
MEG - only measures tangential dipoles, EEG - measures both tangential and radial dipoles
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Is MEG or EEF more spatially precise?
MEG
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Is MEG or EEG better at picking up spikes?
EEG
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Is MEG or EEG less sensitive to deep sources?
MEG
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Is MEG or EEG better at timing?
MEG
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Card 2

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What does MEG measure?

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magnetic fields, generated by the brain

Card 3

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How does MEG differ from EEG?

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Card 4

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What are the implications of an MEG not involving electrical circuits?

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Card 5

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What neurons and potentials are involved?

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