freqdescriptives

Matsuhashi, Masao (NIH/NINDS) matsuham at NINDS.NIH.GOV
Sun Oct 31 20:32:14 CET 2004


Dear Robert,

1. Thanks to your suggestion, now I can somehow calculate and plot the
planar distribution of coherence. It goes something like this.
=============================
% data -> planar gradiometer interpolation (before freq analysis)
cfg.planar         = 'yes';
cfg.planarmethod='fitplane';
dataP=meginterpolate(cfg,data);     %Huge!!
% freq analysis (MTM)
cfg=[];
cfg.method = 'fft';
cfg.foilim = [0,20]
cfg.tapsmofrq=0.5;
cfg.sgncmb = channelcombination({'MEG' 'REF'},dataP.label);
cfg.output     = 'powandcsd'
cfg.pad='maxperlen';
cfg.keeptrials = 'yes'
[freqP] = freqanalysis(cfg, dataP)
% calc coherence
freqPR=freqdescriptives(cfg, freqP)
% combine V/H channels
for n=1:274
    freqPRC.powspctrm(n,:)=mean(freqPR.powspctrm([n;n+274],:));
    freqPRC.powspctrmsem(n,:)=mean(freqPR.powspctrmsem([n;n+274],:));
    freqPRC.cohspctrm(n,:)=mean(freqPR.cohspctrm([n;n+274],:));
    freqPRC.cohspctrmsem(n,:)=mean(freqPR.cohspctrmsem([n;n+274],:));
    freqPRC.labelcmb(n,:)=freqPR.labelcmb(n,:);
    freqPRC.label{n}=freqPR.label{n}(1:5);
end
n=275   %REF channel
freqPRC.powspctrm(n,:)=mean(freqPR.powspctrm([n+274],:));
freqPRC.powspctrmsem(n,:)=mean(freqPR.powspctrmsem([n+274],:));
freqPRC.label(n,:)=freqPR.label(n+274,:)
================================

2. Do you have any suggestion which of three simple interpolation method
('orig' | 'sincos' | 'fitplane') to use in megplanar?
The 'orig' method requires less memory, but seems less reliable.... I
checked with SEF N20m data and the 'orig' method produced four peaks in the
gradient contour map. The 'fitplane' seems best among the three in this
respect, am I right?

3. Thank you for the suggestion of EOG artifact. Finally, I noticed it was
my silly mistake that I found such strange source distribution. I am now
using
>> cfg.funparameter='coh';
Instead of
>> cfg.funparameter='pow';
This way I can see nice picture. Thank you again!!

Regards,
Masaa

------------------------------------------------
Masao Matsuhashi, MD, DMS
NINDS, NIH
Tel: 1-301-594-9139
E-mail: MatsuhaM at ninds.nih.gov
------------------------------------------------




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