source projection

Sanja Kovacevic sanja at UNM.EDU
Fri Aug 19 23:43:42 CEST 2005

Oh, I forgot to mention that I used meplanar with the
source projection option. I tracked the problem down to
axial2planar (line 309 of megplanar: planar.grad =
axial2planar([], axial.grad)). Axial2planar does not
return the field "type" in planar.grad, and therefore
compute_leadfield could not recognize the sensor type and
gives "the forward model does not look like EEG, nor like
MEG" error.


On Fri, 19 Aug 2005 11:42:21 -0600
  Sanja Kovacevic <sanja at UNM.EDU> wrote:
> Hi Robert,
> I've tried using megrealign and megplanar with the CTF
>275 ch data, however I run into problems with source
>projection. First, for megrealign there was a warning
>about the higher order synthetic gradiometer
>configuration. Nevertheless, megrealign ran, but after
>freqanalysis the resulting tfr values for several
>channels were much higher (3 orders of magnitude) than
>for the rest of the channels (which was not the case for
>the original not realigned data). Second, megplanar
>stopped running with "the forward model does not look
>like EEG, nor like MEG" error. I've saved the CTF data
>with the 3rd order noise cancellation on (via newDs
>-filter) and then read these noise canceled data into
>fieldtrip. However, I've only read in MEG and STIM
>channels, I haven't read in the reference channels. Do
>you have any thoughts on what might be going on?
> I appreciate your help,
> Sanja
> On Fri, 12 Aug 2005 14:02:20 +0200
>  Robert Oostenveld <r.oostenveld at FCDONDERS.RU.NL> wrote:
>> Hi Sanja,
>> On 11-aug-2005, at 22:52, Sanja Kovacevic wrote:
>>> I am trying to use
>>>meginterpolate/freqanalysis/combineplanar to get
>>> the tfr
>>> data in the planar gradiometer system, instead of the
>>>original 275
>>> ch axial.
>>> However, combineplanar needs planarchannelset, but this
>>>function is
>>> not
>>> included in the 20050811 distribution. Could you include
>>> function in
>>> the next distribution?
>> Please find the function attached to this mail. I will
>>add it to the  next daily releases, sorry that it was
>> The attached version however does not include the 275ch
>>CTF system  yet, but it is easy to add. You basically
>>only have to make a table  with the planar channel labels
>>that should be combined, and the name  of the combined
>>channel (i.e. the original name). I would appreciate  it
>>if you would send me the table information for the CTF
>>275 system,  I will then update the release version as
>>> I have a set of questions related to meginterpolate: Can
>>> be used
>>> for ploting the planar data? Should I use a default
>>>single sphere
>>> model for
>>> each subject or a single sphere model particular for a
>>>subject for
>>> realignment? Should "nominal" sensor locations be used
>>>as a
>>> template for
>>> each subject, or do you recommend taking an average
>>>across subjects
>>> for the
>>> template?
>> Yes, but only for combineplanar'ed data in combination
>>with  topoplotTFR. It is conceptually not possible to
>>make a topography of  the "raw" planar data itself, but
>>you can do a multiplotER and  multiplotTFR of the planar
>>data. However, that would require another  lay file. The
>>NM122all.lay file is one for the Neuromag system that
>>plots the 122 planar channels at 66 locations, with
>>horizontal and  vertical channel next to each other.
>> If you do not specify a layout in the cfg of
>>multiplotTFR, the  private subfunction createlayout will
>>construct a layout on the fly  based on the gradiometer
>>positions. Usually the plotting is more  controlled with
>>a manually eddited layout file, but the automatic one can
>>serve as starting point. Looking into the code, I
>>now realise  that there still are some loose ends. The
>>megplanar function does not  return the planar gadiometer
>>definition. Please have a look at the  private functions
>>axial2planar and createlayout, and use them  together to
>>construct a planar layout file.
>> best regards,
>> Robert

Sanja Kovacevic
Research Assistant
MIND Imaging Center
Albuquerque, New Mexico, USA
Phone: +1 (505) 272 3327
Fax: +1 (505) 272 4056

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