[FieldTrip] fieldtrip question - help needed

[jan-mathijs schoffelen]

Cara Sara,

I am not sure whether I totally understand your question. Are you  
referring to the example script 'fixing a missing sensor'?
When I look at it on our (renewed) wiki (still brings tears to my  
eyes), I don't see any mention of a layout.

I agree with you that the example however can be made a bit more  
clear. This is my take on it, starting from the back of the pipeline:

The 'fixing' algorithm replaces a 'dead' channel with the average  
signal recorded at its neighbours. In the current implementation, the  
description of the sensors and the data (=the grad-structure and the  
data.trial) which go into ft_channelrepair need to contain a full  
description of the sensor-array, including the faulty one. In other  
words, if your sensor array has 10 sensors, one of which you want to  
have repaired, the input to ft_channelrepair needs a data-structure  
containing data from the spatial location of those 10 sensors (this is  
in data.grad, and needed to determine which channels are the  
neighbours). For consistency, the time course of the faulty channel  
also needs to be there. The actual time courses of the faulty channel  
will not be used, and these can take any value. Depending on the  
hardware and recording protocol, a faulty channel is either present or  
not in the data. In the example script, the faulty channel was not  
even recorded, and this is the reason for the first part of the  
script: the creation of a dummy channel, initialized with 0's in order  
to make ft_channelrepair work. If, however, your dataset actually  
contains data on the faulty channel (which may look very noisy), you  
can skip the first part of the script, and directly go to the second  
part.

Best wishes,

Jan-Mathijs


On Jan 13, 2011, at 4:09 PM, s.rombetto at cib.na.cnr.it wrote:

> Hello
> can anybody spend some more words on the chapter "Fixing a missing  
> sensor"?
> I'm trying to use it with a AtB (like ITAB-Chieti) device...but I
> cannot understand how to use it. I've several troubles when I've to
> declare the layout, since I don't have a layout file, but I construct
> that starting from grad...
> Do you have any hint for me?
>
> Sara Rombetto
>
>
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Dr. J.M. (Jan-Mathijs) Schoffelen
Donders Institute for Brain, Cognition and Behaviour,
Centre for Cognitive Neuroimaging,
Radboud University Nijmegen, The Netherlands
J.Schoffelen at donders.ru.nl
Telephone: 0031-24-3614793