[FieldTrip] how to set lambda for resting state lcmv-beamformer

[Frederic Roux]

Dear fieldtrip users,

I am trying to compute a spatial filter
to localize alpha-band activity in an
eyes closed resting state meg recording
using the LCMV-method.

The condition of my covariance matrix is > 1*10e6
so I set lambda = 0.01. When I then plot the NAI
I find two clusters of activity: 
one in the center of the head,
one in the occipital cortex.

In Exercise 5 of the tutorial, it is 
mentioned to set lambda to 1e-29 in order 
to suppresses the center of head artifact.

I wanted to ask if anybody could tell me what the
rationale was to set lambda = 1e-29? 
Is there a standardized way to compute lambda?

Best regards,

Fred

-- 
Frédéric Roux, PhD student
Department of Neurophysiology
Max Planck Institute for Brain Research
D-60529 Frankfurt am Main
Frederic.Roux at brain.mpg.de
+49(0)69630183225

 		 	   		  
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