[Eeglablist] has anyone used an actiCHamp and an ActiveTwo?

Fri Nov 9 04:49:27 PST 2012

Can't comment on 128 vs 64 ... but I have been using the Brain Products ActiChamp 64-channel system for about a year now. Things are great compared to a passive electrode system. We've been using a mannequin head to the mount the electrodes and then place on the subject. This has been fine since, the subject can read and fill out the IRB forms while you're placing the electrodes on the mannequin.

In terms of cost .. the Brain Products system was cheaper than BioSemi when I was searching around... I was choosing between BioSemi and BrainProducts.

I remember reading Pascual-Marqui's dipole error localization for 64 electrodes and above ... the error curve saturates near ~70 electrodes for a single "epileptic dipole" near the surface. This may not be case for other ERPs, and this may relate to Arnaud's comment.

Jason ... I have a friend who recently purchased a 256 BP actichamp system .... I can put you in contact with him

----------------------------------
Andrew Dimitrijevic PhD
Assistant Professor
Communication Sciences Research Center
https://csrc.cchmc.org/
Cincinnati Children's Hospital
Department of Otolaryngology, University of Cincinnati
3333 Burnet Ave. - S1.313
MLC 15008
Cincinnati, OH 45229-3026
tel. 513.636.3469
andrew.dimitrijevic at cchmc.org
http://csrc.cchmc.org/andrew-dimitrijevic

________________________________
From: eeglablist-bounces at sccn.ucsd.edu [eeglablist-bounces at sccn.ucsd.edu] on behalf of Arnaud Delorme [arno at ucsd.edu]
Sent: Thursday, November 08, 2012 9:16 PM
To: Patrick Simen
Cc: eeglablist at sccn.ucsd.edu
Subject: Re: [Eeglablist] has anyone used an actiCHamp and an ActiveTwo?

I disagree with Baris and Patrick. 128-channels is better than 64 in many ways. I had done some testing on source localization (comparing dipole localization error from 256 (ground truth) down to 19 electrodes) and below 72 channels, the error starts to increase (not published unfortunately).

Only record with 64 channels if you do not have the choice. If you are planning to scan electrode positions, use 128. If you are planning to coregister with the subject's MRI, definitely use 128.

In choosing between Biosemi and Brainproduct, Biosemi systems are less expensive than Brainproduct. However, with Biosemi, you cannot check electrode impedances. If you have the funds, you might want to get the Brainproduct system. If your funds are limited, you might want to get Biosemi. And remember there is also Neuroscan, EGI, Ant and Guger Technologies who all offer decent products as well.

Best,

Arno

On 8 Nov 2012, at 05:02, Patrick Simen wrote:

I only have experience with ActiCHamp, so it may be true that BioSemi is better.

However, I just wanted to say that I haven't found it at all difficult to reduce impedance with the BrainProducts system. It also didn't feel uncomfortable to me when I wore the cap several times and had the electrodes inserted by students (nor when I inserted them myself -- it was easy enough that I could prep myself completely and quickly without assistance from anybody else -- I just needed a handheld mirror to see the occipital electrodes).

The only thing I really noticed was that reducing impedance was far (!!) easier and more comfortable than the usual process with passive-electrode caps in my previous lab. But that would probably be true with any active electrode cap, I guess.

Incidentally, an engineer at Brain Products also told me something that agrees with what Baris says below: there's not much point in going beyond 64 electrodes.

Best,

Pat.

On Nov 7, 2012, at 11:10 PM, Baris Demiral wrote:

Yes I have experience with both. Use BioSemi. Here is my reasoning:

I used full BioSemi Active2 system (cap+amplifier+LabView+response bix etc.) Electrodes are easy to insert, small, easy to reduce impedance, comfortable. You put the gel before the electrodes are placed.

I used BProduct Active electrodes with Neuroscan amplifier+electrode box. Electrodes are very large, not easy to place the elctrodes on the cap, subjects feel discomfort. In order to reduce this effect you may need to place the electordes on the manican before you put it on the subject which is weird. Since you will have 128 electrodes !! Also, you ned to insert the gel after you put the electrodes through a small opening, which makes impedance reduction relatively hard to obtain.
Kinking problem is likely to occur due to the difficulty of placing the electrodes.

Buy BioSemi. even 64 channel is fine for many applications and source localization. 128 too much and not very necessary (read some papers related to source localization, you will notice that after 60 channels quality does not change much). Kinking proble is likely to occur due to the orientation of the cable placed initially in the beginning.

Feel free to call me if you need further help. But, I would suggest (if you are going to pay a lot of money in this business) go and observe the systems in the labs live.
Baris

On Fri, Nov 2, 2012 at 11:42 AM, Jason M Cowell <cowell at uchicago.edu<mailto:cowell at uchicago.edu>> wrote:
Hello,

Our lab is presently in the process of acquiring several active 128- electrode systems. Does anyone have experience with both the Brain Products actiCHamp and the BioSemi ActiveTwo? We are comparing both and are interested in the quality of these data, particularly in noise issues. Are either of the systems more compatible with EEGLAB? Any help or experience, particularly using the actiCHamp would be greatly appreciated.

Jason

Jason M Cowell, Ph.D.
Postdoctoral Scholar
Social Cognitive Neuroscience Lab
University of Chicago
5848 S. University Ave.
Chicago, IL 60637

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S. Baris Demiral
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Patrick Simen, Ph.D.
Assistant Professor, Neuroscience Department
Oberlin College
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www.oberlin.edu/faculty/psimen<http://www.oberlin.edu/faculty/psimen>

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