[Eeglablist] CSD maps in STUDY design

[Craig E. Tenke]

Dear Arno:

Your advice to Marco on how to use CSD with spectral data is incorrect. 
The Laplacian /must/ precede the spectral computation. If the the 
spectral transformation is done first, the result is /not /an 
interpretable CSD. The implications of this error can be quite profound 
(cf. Fig. 1 of Tenke and Kayser, 2005). As a general rule, a CSD 
transform can only be applied to linearly-transformed surface potential 
data to be physiologically meaningful, although the underlying algorithm 
can be applied to any data, as shown by your example.

regards from NY,

Craig Tenke
Jürgen Kayser


On 1/18/2013 8:59 PM, Arnaud Delorme wrote:
> Dear Marco,
>
> based on another email I sent earlier to the list.
>
> /% merge all channel location structures for the STUDY/
> /mergelocs = eeg_mergelocs(ALLEEG.chanlocs);/
> ////
> /% get ERSP results (scalp maps) - for example scalp topography of 
> spectrum in the alpha band/
> /[STUDY spec ] = std_specplot(STUDY,ALLEEG,'channels', { 
> mergelocs.labels }, 'topofreq', [8 12]);
> /
> /
> /
> then you may use one of the many laplacian function eeg_laplac.m is a 
> good one although you will have to rebuild a dataset to use it. 
> Something like
>
> /TMP = EEG(1);/
> /TMP.chanlocs = mergelocs;/
> /TMP.data = squeeze(spec{1});/
> /CSD = eeg_laplac(TMP, 1);/
>
> /% plot average CSD scalp topography/
> /average_CSD = mean(CSD,2); % average across subjects/
> /figure; topoplot(average_CSD, mergelocs);/
>
> Best,
>
> Arno
>
>
> On 17 Jan 2013, at 13:56, Marco Montalto wrote:
>
>> Dear List,
>>
>> Is there a way of producing CSD (current source density) maps in 
>> EEGLAB, in a STUDY design?
>>
>> Marco Montalto

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