71210 Bioelectromagnetism - Exercises Autumn 2004

Magnetoencephalography

1. Inhomogeneities do not affect MEG lead field flow lines in a cylindrically symmetric case
   1. True
   2. False
2. Referring to the previous question, does the poorly conducting skull have an effect on MEG lead field in realistic case
   1. No
   2. yes
3. Ideal MEG sensors should exhibit a large gain relative to the brain activity and should simultaneously effectively attenuate the environmental noise. Two coils wound in opposite directions may be used to cancel the earth's magnetic field. This kind of sensor is called
   1. gradiometer
   2. radiometer
   3. magnetometer
4. Comparison of MEG and EEG half sensitivity volumes indicates that
   1. they exhibit similar sensitivities, depending on the recording configuration
   2. MEG exhibits more concentrated half-sensitivity, since the poorly conducting skull has no significant effect on lead fields
   3. EEG exhibits clearly more concentrated half-sensitivities in each channel, since the number of channels may be larger

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