[FieldTrip] Problem with EEG channels in ft_neighborselection when running cluster statistics

["Jörn M. Horschig"]

Hey Stephen,

You need to specify the position of your electrodes, which are mostly 
stored in an 'elec' structure. If you do not have that available, you 
can circumvent the problem by defining a cfg.layout. In that case, 
neighbouring sensors will be selected according to how they are placed 
in that layout-file you specify. That's not 100% correct of course, but 
at least an estimate how the sensors are positioned (note that a layout 
has only 2D coordinates). For example, you could use cfg.layout = 
'EEG1010.lay' as a start.

Anyway, could you try using a more recent version of FieldTrip? A few 
months ago, we changed the way the neighbourselection works (actually, 
you have to call cfg.neighbours = ft_neighbourselection manually, now). 
You can then also check with cfg.feedback = 'yes' whether the 
neighbourselection looks alright to you (that's the same as calling 
ft_neighbourplot)

Hope it helps! Best regards,
Jörn



On 9/17/2011 6:42 PM, Stephen Politzer-Ahles wrote:
> When attempting to run cluster statistics on my EEG data (originally 
> from Neuroscan .CNT, then processed in EEGLAB and finally imported to 
> fieldtrip) using ft_timelockstatistics(), I receive the following 
> error message:
>
> ??? Error using ==> ft_neighbourselection at 114
> Did not find gradiometer or electrode information.
>
> Error in ==> statistics_wrapper at 241
>     cfg.neighbours = ft_neighbourselection(cfg,varargin{1});
>
> Error in ==> ft_timelockstatistics at 123
> [stat, cfg] = statistics_wrapper(cfg, varargin{:});
>
> This seems to be because when I use cfg.channel = {'EEG'}; with my 
> data, the channel information (the variable "sens" used in 
> ft_neighbourselection) consists only of the list of channel labels:
>
> sens =  {'FPZ'    'CPZ'    'FP2'    'F7' .........}
>
> On the other hand, when I run timelockstatistics on the sample data 
> from the wiki, "sens" includes much more information:
>
> sens =
>
>       pnt: [151x3 double]
>       ori: [356x3 double]
>       tra: [184x356 double]
>     label: {151x1 cell}
>      unit: 'cm'
>
> I think most of that extra information is planar gradient data (i.e., 
> it comes from GA_FIC.grad). Since my data are EEG data, I assume it 
> wouldn't make sense to use ft_megplanar on them. So, assuming that I 
> need to get the extra channel location information into my EEG data, 
> does anyone have any ideas on how to do that?
>
> Best,
> Steve Politzer-Ahles
>
> -- 
> Stephen Politzer-Ahles
> University of Kansas
> Linguistics Department
> http://www.linguistics.ku.edu/
>
>
> _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip


-- 
Jörn M. Horschig
PhD Student
Donders Institute for Brain, Cognition and Behaviour
Centre for Cognitive Neuroimaging
Radboud University Nijmegen
Neuronal Oscillations Group

P.O. Box 9101
NL-6500 HB Nijmegen
The Netherlands

Contact:
E-Mail: jm.horschig at donders.ru.nl
Tel:    +31-(0)24-36-68493
Web: http://www.ru.nl/donders

Visiting address:
Trigon, room 2.30
Kapittelweg 29
NL-6525 EN Nijmegen
The Netherlands

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