[Eeglablist] responses to "Time to apply 128 electrodes"

[Jim Kroger]

When I posted this request I must have used "reply to all" as the 
responses came to me instead of the list. I've compiled them here for 
interested readers and archival purposes. Thanks for the responses, 
and apologies if I omitted any response.
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From: "Li Yong" <liyong98 at mails.tsinghua.edu.cn>

It is very easy to place electrodes in the EEG system of biosemi company.
It takes me only about no more than half an hour to fix all 128 electrodes.
The neuroscan systme may be difficult to fix electrodes.
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From: "Li Yong" <liyong98 at mails.tsinghua.edu.cn>

I always do the experiment alone.
In the neuroscan system, the electrodes and wires are both in the 
cap, you had to arrange the cap while applying electrode gel .Because 
no electrodes or wires are attached to the cap of the biosemi system, 
the only thing need to do is separating the hair when electrode gel 
is applied. And the active electrodes make it no use to detect the 
residence below 50 K ohm. So the preparation time for experiment is 
reduced. You can get more details in the www.biosemi.com.

The more electrodes the better. In the 128 system, there is also much 
difference between the EEG recorded from neighbor electrodes on the 
scalp.
The average inter-electrode distance of 128 system is about 2.25 cm, 
and that of 64 system is about 3.3 cm.  EEG system with the distance 
between electrodes averaging less than 2.5 cm can provide sufficient 
topography [1].


[1]  A. Gevins, et al. High resolution EEG: 124-channel recording 
spatial deblurring and MRI integration methods. Electroenceph. Clin. 
Neurophysiol., 1994, 90: 337~358.
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From: "Joe McArdle \(NIDCD\)" <mcardle at nidcd.nih.gov>

Hi Jim, it takes a long time. I beta tested the 128 system and with 2 other
people helping me it took well over an hour to get decent impedance values.
I use a 64 channel quick cap now and it takes about 40 minutes if I work
alone. I've used EGI caps and Neuroscan quickcaps. I like the quickcap
better. Also the newly reformulated quickgel works great, and does not
require prepping the electrodes.

You know, there is a Neuroscan list similar to this one. You should join it
and ask your question there. You will probably get lots of helpful advice. I
always have when I've asked.

Best of luck,, Joe
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From: "Maurits, NM" <n.m.maurits at neuro.azg.nl>

Dear Jim,

We have a 128-channel system where we use ElectroCap  head caps. It 
takes an experienced technician 20-30 minutes to apply all electrodes 
using a syringe and a blunt needle. We use a mixture of 50% normal 
paste and 50% scrub paste. We aim at getting all impedances  below 20 
kOhm, but in practice most are between 3-10 kOhm. We have a TMS 
headbox (Dutch company)  and measure using Onyx software (also 
Dutch). Hope this helps.

Best regards,
Natasha Maurits.
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From: M D <astramia at yahoo.com>

Hi Jim

We just ran an experiment with 24 participants. The 128 electrode cap 
took approx 40 minutes to one hour to apply to a participants head 
depending on our ability to get impedances down. We also ran approx 8 
other physiological measures, but I am trying to give you an estimate 
of about how much time the 128  lead cap took.
I had help from Jeremy who is experienced in these matters and he 
made all the difference in the world as he was able to get impedances 
down pretty fast so it may take longer for someone who is not 
experienced at getting impedances down.

Margery Doyle at <mailto:mdoyl at ai.uwf.edu>mdoyl at ai.uwf.edu
Jeremy Higgins <mailto:jhiggins at ai.uwf.edu>jhiggins at ai.uwf.edu
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From: M D <astramia at yahoo.com>

Hi
  We were using a NeuroScan with an Electro Cap International 128 lead 
cap system and we did  have two people working on one participant at 
a time. However, Jeremy did do most of the impeadance work. I helped 
put electrode gel in the holes and put all the other 
psychophysiological electrodes on the participant.
Hope that additional information helps
Margery Doyle UWF IHMC
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From: "Dykman, Roscoe A" <DykmanRoscoeA at uams.edu>

It takes no longer than-10-15 minutes in babies. Ross Dykman
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From: Darren Weber <Darren.Weber at flinders.edu.au>

Hi Jim,

I allow 2 hours.  It can be quicker, but I've found it better to 
allow the extra time, in case some electrodes are difficult.  Also, 
dont forget about quick insert electrodes.  Impedance testing is 
important, but sometimes I have to settle for < 10 kOhms rather than 
5 kOhms on all electrodes.
There are some differences between caps and gels etc., but it's too 
hard to discuss this here.  I've mainly used ECI electro-caps (tin).

Best regards, Darren
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From: Theresa Vaughan <vaughan at wadsworth.org>

Hi Jim,

Seems like a long time. We use a 64-channel Electrocap.  It takes 
about 15 minutes. I have never done one with 128 channels but I think 
that the additional channels would add too much time.

Theresa