http://www.nature.com/scitable/blog/brain-metrics/what_does_meg_measure?isForced
ID: 174108 • Letter: H
Question
http://www.nature.com/scitable/blog/brain-metrics/what_does_meg_measure?isForcedMobile=Y from the article answer
1. What is an EEG? Why has it been difficult to match components of the EEG to specific sources in the brain?
2. What does an MEG measure? What role has SQUID played in the development of MEG devices?
3. What are the advantages of MEG over functional magnetic resonance imaging (fMRI) for studying brain function?
4. What is the ultimate source of the tiny changes in magnetic fields detected by MEG?
Explanation / Answer
1. What is an EEG? EEG stands for electroencephalogram. It is a test used to record and detect the abnormalities in the electrical activity of the brain.
Why has it been difficult to match components of the EEG to specific sources in the brain?
The entire brain produces EEG signals. However, it is very difficult to match the signals to the portion of the brain from where it originates. This is because the EEG signals are detected first and then we attempt to work backwards and identify the portion of the brain from where it has originated. This is called the inverse problem.
2. What does an MEG measure? What role has SQUID played in the development of MEG devices?
MEG measures the magnetic fields that are produced due to the electrical activity of the brain.
SQUID, is an extremely sensitive magnetometer. It operates on the principle of quantum physics. It is a very precise instrument which is capable of accurately detecting the very small magnetic fields produced in the brain. Without the sensitivity of SQUID, the development of the MEG would perhaps have been impossible.
3. What are the advantages of MEG over functional magnetic resonance imaging (fMRI) for studying brain function?
In MEG, the activity of the brain can be followed with millisecond precision. In MRI (of which fMRI is a part) the response of Hydrogen atoms to radio waves in a magnetic field is utilized to detect changes. However, in MEG the magnetic fields produced by changes in the neural activity is measured. Hence, MEG would be expected to be more accurate. With fMRI it is not possible to accurately pinpoint the time of neural activity.
4. What is the ultimate source of the tiny changes in magnetic fields detected by MEG?
The electrical activity in the brain is the source of the tiny changes in the magnetic fields detected by MEG.
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