Wrong 3D chip?

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Wrong 3D chip?

Post  mcs on Wed Jun 11, 2008 3:12 am

Hi all!

I am trying to use the 3D chip MEA setup with acute hippocampal slices, and I was very happy, that I could see some really nice fEPSPs. However, when I fixated the slice with 4% formaldehyde, the fields still remained. They responded to KCl application, namely the amplitudes decreased. I removed the slice, but the fields were still there. Curiously, the signals were not present on the adjacent electrodes to the stimulator, but to 2 rows away. These “fEPSPs” are in the range of the biological signals (400-600 uV), and the waveform looks like a nice field in the CA1 str. radiatum. I used a biphasic (-1 to 1 V, 100 us) signal.

My question is: is it possible, that the brand new 3D chip is wrong? How can you explain, that upon stimulation (no slice is in the chip), you see signals on electrodes being far away from the stimulator, but not on neighboring points? This phenomenon is valid on practically every electrode, and not limited to “high” stimulus voltage, it is observable using really low (100 uV) voltage. I have tried a 2D MEA chip, and that works nicely.

Thanks for your response.

mcs

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Re: Wrong 3D chip?

Post  mcs on Wed Jun 11, 2008 3:13 am

Dear Szeg,

It seems, that you do observe stimulus artifacts on the 3D MEA, whereas they are not observed on a regular MEA.
It is quite common, that these artifacts are not just on electrodes near the stimulus electrode, but they can occur also on electrodes with close connecting lanes to the contact pads.

Are you operating a Blanking circuit system? If yes, do the artifacts disappear when blanking is enabled?
Did you set the SynchOut and select (and download) your stimulus electrode in MEA select?
Did you use the yellow spacer provided with the 3D MEA? If that one is not used the contacts from the glas insert to the PCB carrier will be damaged when inserted in the amplifier.

If you cannot solve your problem by checking this simple issues, please mail us screenshots, stimulus protocol and numbers of involved MEAs to support@multichannelsystems.com

Greetings

Thomas

mcs

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Re: Wrong 3D chip?

Post  mcs on Wed Jun 11, 2008 3:13 am

Dear Thomas,

Thanks for your response. Yes I agree, these signals must be stimulus artefacts. The main question is why are they so huge, and sometimes why are they look like a real fEPSP? I have checked the point you suggested again, but the situaton did not improve. I will send you an email with more data provided.

Best regards:

Szeg

mcs

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Re: Wrong 3D chip?

Post  mcs on Wed Jun 11, 2008 3:13 am

Great,

I hope the data will clarify the situation...

Thomas

mcs

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