[FieldTrip] ICA - not applying the backprojection matrix to the sensor description - Why?

[Grazia Di Pisa]

Dear all,

I’m currently trying to do ICA to remove eye blinks from my EEG data.
I've basically used the script on the tutorial, and even thou it says ‘removing 4 components’ then it gives me 'not applying the backprojection matrix to the sensor description’.

	<<	detected 0 visual
                removing 4 components
		keeping 57 components
		processing trials
		processing trial 166 from 166

		not applying the backprojection matrix to the sensor description
		the call to "ft_rejectcomponent" took 1 seconds and required the additional allocation of an estimated 245 MB	>> 

Shouldn’t it be 'applying the backprojection matrix to the sensor description’ in order to be effective?
If someone could give some explanation, it would be very much appreciated!

This is the script I used:

    cfg        = [];
    cfg.method = 'runica'; 
    cfg.channel = 'EEG'; 
    
    comp = ft_componentanalysis(cfg, data);

%% Identify the artifacts:

    figure
    cfg = [];
    cfg.component = 1:30;       
    cfg.layout    = 'biosemi64.lay'; 
    cfg.comment   = 'no';

    ft_topoplotIC(cfg, comp)

%% Further inspection of the time course of the components:

    cfg = [];
    cfg.layout = 'biosemi64.lay'; 
    cfg.viewmode = 'component';

    ft_databrowser(cfg, comp);                                             

 %% Remove components and backprojecting:
  
    cfg = []; 
    cfg.component = [2 53 54 61]; % to be removed component(s)
    cfg.demean   = 'no';
    cfg.updatesens = 'yes';

    data.ica.analysed = ft_rejectcomponent(cfg, comp);


best,
~ grazia




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