Dear Urs,
It's actually the other way around. Electrodes close to the reference
have lower amplitude responses and the reference itself will be zero.
This would be taken into account if we had forward model computation
for different references. Since at the moment we don't have this
feature you should switch to average reference and then it wouldn't
matter what the original reference was.
Best,
Vladimir
On 20 May 2011, at 11:42, Urs Bachofner <[log in to unmask]> wrote:
> Hi Vladimir!
>
> Thanks a lot for your last answer, apparently I'm not the only one who had this question.
>
> But I have another one that I already mentioned in my last E-mail:
>
> Considering the location of the reference electrode in different EEG nets, it should be clear that electrodes closer to that reference will have a higher amplitude recorded than electrodes which are more distant. I'm not exactly sure how big and relevant this difference is but shouldn't we have a preprocessing step that alleviates this bias by checking the coordinates of the electrodes involved and their distance to the reference electrode?
> I think if we don't eliminate this bias we will always have an overestimated activation around the reference electrode in 3D source localisation.
>
> Thanks a lot for your opinion in this matter.
>
> Urs
>
>
> Am 20.05.2011 12:19, schrieb Vladimir Litvak:
>> see
>>
>> http://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=SPM;5681190f.1105
>>
>>
>> On 20 May 2011, at 10:54, Jing Kan<[log in to unmask]> wrote:
>>
>>> Dear SPM experts,
>>>
>>> May I ask a basic question about the data-preprocessing?
>>>
>>> In terms of the SPM tutorial I read, we can do the preprocessing either
>>> with the order "epoch" and then "filter" or "filter" and then "epoch".
>>>
>>> May I ask is it any effect with these two different ways?
>>>
>>> Many thanks,
>>>
>>> Jing
>
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