[FieldTrip] Separating MEG/EEG data

[Stephen Whitmarsh]

Hi Mona,

I'm not sure I understand your question but ill give it a go:

In Elekta, labels of magnetometers end in 1, (e.g. MEG10*1*), gradiometers
in (e.g. MEG22)2 and 3. The latter are the orthogonal 8-shaped coils that
are often combined, e.g. using ft_combineplanar. This will reduce the 204
gradiometers in 102 combined gradiometer, that FT assigns labels to,
showing you which sensors are combined, e.g. "MEG102+MEG103".

If you use ft_selectdata, or a cfg.channel configuration field, you can use
* as I mentioned before, or ? and other wildcards such as MEG, and MAG, to
select sensortypes.

Hope this helps,
Stephen

On 19 October 2016 at 18:42, Wong-Barnum, Mona <mona at sdsc.edu> wrote:

>
> Thanks Stephen, your code was very helpful (:
>
> My data has 2 gradiometers but it appears that there is only a single
> megplanar channel type.  Is there a way to further separate the 2
> gradiometers?
>
> Mona
>
>
> On Oct 18, 2016, at 10:22 PM, Stephen Whitmarsh <
> stephen.whitmarsh at gmail.com> wrote:
>
> Hi Mona,
>
> To add to Tzvetan:
>
> - You can in many FieldTrip functions specify on which channels you want
> to work (cfg.channel), e.g. in ft_preprocessing.
> - You can also split the data later using ft_selectdata, e.g.:
>
> cfg = []
> cfg.channel = 'MEG';
> data_MEG = ft_selectdata(cfg,data_combined);
>
> cfg = []
> cfg.channel = 'EEG';
> data_EEG = ft_selectdata(cfg,data_combined);
>
> - To selecting magnetometers or gradiometers you can use:
> cfg.channel = 'MEG*1'
> cfg.channel = {'MEG*2', 'MEG*3'}
>
> Cheers,
> Stephen
>
>
> On 19 October 2016 at 01:17, Wong-Barnum, Mona <mona at sdsc.edu> wrote:
>
>>
>>         I have Elekta Neuromag .fif files which contains MEG and EEG
>> data.  What steps do I need to do to separate the MEG from EEG and the 3
>> different MEG sensor data (magnetometer, 2 gradiometer)?
>>
>>         I have been looking through the FieldTrip documentation but
>> haven’t found what I need.  All help is appreciated.
>>
>> thanks,
>> Mona
>>
>>
>> *********************************************
>>     Mona Wong
>>     Web & iPad Application Developer
>>     San Diego Supercomputer Center
>>
>>     "Strive not to be a success, but
>>     rather to be of value."
>>                                 --- Albert Einstein
>> *********************************************
>>
>>
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>
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>
> *********************************************
>     Mona Wong
>     Web & iPad Application Developer
>     San Diego Supercomputer Center
>
>     "To handle yourself, use your head;
>     to handle others, use your heart."
>
> -- Eleanor Roosevelt
> *********************************************
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