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MCE User’s Guide MCE windows and dialogs
NM20600A-A 2004-05-17 23
Figure 12 Minimum norm estimate options dialog
The [Regularization] slider and text field select and show the number of singu-
lar values of the data used in the estimate. If the noise level in the measurement
is low, increase the value to correctly estimate more complex source distribu-
tions. If the noise level is high, decrease its effect by decreasing the value. The
default value (30) is usually reasonable for averaged evoked responses.
Keeping the [Depth normalization] button pressed compensates for the ten-
dency of the estimate to produce too superficial sources.
The Elekta Neuromag™ and Vectorview™ have both magnetometer and gradi-
ometer sensors. In the estimation, the signals are analyzed in relation to the
noise level. The default values (5 fT/cm for gradiometers, 25 fT for magnetom-
eters) are reasonable in evoked response measurements, but if for some reason
their relative noise level changes, you can modify the values in this dialog. Press
the [Set noise levels manually] button and change the values in the text fields.
If the options are changed, the windows displaying the previous estimate are
closed.
Warning: If the regularization parameters are changed from the default ones,
the new values must be validated using known data.
12.3 Pre-processing dialog
The pre-processing dialog is opened by pressing the [Preprocessing] button in
the Options menu or automatically when you select a new data file.
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