[Eeglablist] Low density system questions

[Scott Makeig]

Usually the 'CNS' reference electrode is (in Biosemi) part of a CNS-DRL
pair. If it is here a single reference electrode then you should'nt need to
rereference unless you want to do source analysis. But remember that
electrodes placed near the reference channel will record very little
signal, because they and the reference will have nearly the same signal,
and each EEG channel is the difference between two (or more) electrodes.

Scott

On Sat, May 2, 2020 at 5:04 PM Fran Copelli <fcopelli at ryerson.ca> wrote:

> Hi Scott — thanks for your reply — but the system is actually the Starstim
> 20 from Neuroelectrics; we are using 18 scalp channels following a 1020
> system layout. I’m not sure if the same rule applies to this system— can
> you advise?
>
>
> On May 2, 2020, at 4:45 PM, Scott Makeig <smakeig at gmail.com> wrote:
>
> 
> If you are using a Biosemi system (with CMS-DRL electrodes) then you must
> re-reference to eliminate a <=40 dB noise contamination (see the Biosemi
> website). You may reference as you wish -- using average reference is
> typically a good choice.
>
> Scott Makeig
>
> On Sat, May 2, 2020 at 8:40 AM Fran Copelli <fcopelli at ryerson.ca> wrote:
>
>> Dear list,
>>
>> My colleague is collecting data using a low density (18 channel) system.
>> With so few channels, what are the guidelines regarding a) whether noisy
>> channels should be deleted or interpolated and b) what is the maximum
>> value
>> to remove and still have interpretable data.
>>
>> My second question is regarding referencing. The manual for the system
>> suggests that all data is referenced to CMS. Should we be rereferencing to
>> another channel/to the average? Is average referencing suitable for such a
>> low density system? Note that there are no mastoids to reference, only
>> scalp and eye channels.
>>
>>
>> Thanks very much and looking forward to hearing any suggestions,
>>
>> Fran
>>
>> Fran
>>
>> SMART Lab, Psychology Department
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>
>
> --
> Scott Makeig, Research Scientist and Director, Swartz Center for
> Computational Neuroscience, Institute for Neural Computation, University of
> California San Diego, La Jolla CA 92093-0559, http://sccn.ucsd.edu/~scott
>
>

-- 
Scott Makeig, Research Scientist and Director, Swartz Center for
Computational Neuroscience, Institute for Neural Computation, University of
California San Diego, La Jolla CA 92093-0961, http://sccn.ucsd.edu/~scott