Activation vs. baseline

[Pascal Fries]

Dear Valdimir,

OK. I had been asking, because coherence (and also power) have a bias that
is sample size dependent. For those measures, particularly for coherence, I
would suggest to use equal sample sizes.

As far as I can judge, this problem is not there for amplitude.

Then it is to the cluterrandanalysis experts to help you with that
particular analysis.

Best, Pascal


  _____

From: FieldTrip discussion list [mailto:FIELDTRIP at NIC.SURFNET.NL] On Behalf
Of Vladimir Litvak
Sent: Monday, February 27, 2006 10:13 AM
To: FIELDTRIP at NIC.SURFNET.NL
Subject: Re: [FIELDTRIP] Activation vs. baseline



Amplitude at the sensor level.



Vladimir



-----Original Message-----
From: FieldTrip discussion list [mailto:FIELDTRIP at NIC.SURFNET.NL] On Behalf
Of Pascal Fries
Sent: Monday, February 27, 2006 11:05 AM
To: FIELDTRIP at NIC.SURFNET.NL
Subject: Re: [FIELDTRIP] Activation vs. baseline





Dear Vladimir,



what aspect of the two data pieces are you comparing? Power? Coherence?
Amplitude? At the sensor or at the source level?



Best, Pascal





Pascal Fries
Principal Investigator
Neuronal Coherence Group
F. C. Donders Centre for Cognitive Neuroimaging
Radboud University Nijmegen

Kapittelweg 29
6525 EN Nijmegen
The Netherlands

Phone: (+31) (0)24 36 10657
Fax:   (+31) (0)24 36 10989
e-mail: pascal.fries at fcdonders.ru.nl
website: www.ru.nl/fcdonders/






  _____


From: FieldTrip discussion list [mailto:FIELDTRIP at NIC.SURFNET.NL] On Behalf
Of Vladimir Litvak
Sent: Monday, February 27, 2006 9:24 AM
To: FIELDTRIP at NIC.SURFNET.NL
Subject: [FIELDTRIP] Activation vs. baseline

Dear Eric and all,



I'm playing with 'Activation vs. baseline' option in clusterrandanalysis.
The problem is that my baseline is about 100ms while the activation period
is 300 ms. I cannot extend the baseline since the raw data I have is already
segmented. What is the right thing to do in this situation? Should I divide
the activation period into 3 segments and test them separately? Or maybe
replicate the baseline 3 times, concatenate and use this as baseline for the
whole period?



Thanks,



Vladimir

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