Elektra Beckum NM20600A-A User Manual
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.
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
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.
closed.
Warning: If the regularization parameters are changed from the default ones,
the new values must be validated using known data.
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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