OK, my mistake. I'm not an EGI expert. I just remember there was this reference issue there.
Vladimir
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On 6 Aug 2010, at 18:03, Yury Petrov <[log in to unmask]> wrote:
> Vladimir, EGI has 129 or 257 channels, 1 of them is a reference. So there are 128 working channels in my EGI setup, for example. I am also not using the reference channel in my software, but I am thinking about doing it, it only makes sense when the average reference frame is used.
>
> On Aug 6, 2010, at Aug 6, 2010 | 12:55 PM, Vladimir Litvak wrote:
>
>> Dear Yury,
>>
>> In EGI there are 127 normal channels and one reference. It doesn't have an EGI-like name and there was no location for it in the location files we got from EGI. So presently it's not treated as EEG channel. This might explain your problem. In principle, this can be fixed but there has not been strong pressure from the EGI community to do this until now.
>>
>> Vladimir
>>
>> Sent from my iPad
>>
>> On 6 Aug 2010, at 17:30, Yury Petrov <[log in to unmask]> wrote:
>>
>>>> And how can one get the lead field matrix from SPM once it was calculated for my electrode locations?
>>>>
>>>>
>>>> If you do all the steps for inversion in SPM for some dataset using the template head, the first time you do an inversion leadfields will be computed and stored in the file whose name starts with SPMgainmatrix.... This is just a mat file, nothing fancy.
>>>
>>> Hi, Vladimir
>>>
>>> I used the Template cortex and egi128_GSN_HydroCel.sfp electrodes file, and I got the gain matrix 'G' from the SPM... file, but its first dimension is only 127 instead of 128. The 'label' variable from the same file has all 128 labels correctly. Any ideas?
>>>
>>> Yury
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