Testing MEA impedance with Matlab

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Testing MEA impedance with Matlab

Post  mkuykendal on Wed Apr 18, 2012 5:22 am

Hi MCS,

In my experimentation I use a MEA1060-Up-BC amplifier coupled with an STG2004 and Matlab. I control all of my stimulation routines with Matlab, and I'm interesting in incorporating a method for impedance testing on-the-fly prior to each experiment. This is very important because as the electrode arrays degrade, I need to provide more current to evoke neuronal action potentials, and I need to have a method for determining an appropriate stimulation range based on the electrode impedance. Additionally, I am doing triggered electrical recording with MCRack, and I'm wondering if there a way to load the electrical recordings directly into Matlab.

Ideally, I would like to have a Matlab function that will send a very small current to the MEA (which I can already do), trigger an electrical recording in MCRack (also already doing), load the electrode raw data file "Ztest.mcd" into Matlab (don't know how) and then extract the voltage from the trace (I'm not sure how to stimulate with a sine wave to measure the complex impedance). Also, perhaps it is mostly the resistive portion of the impedance that is really changing (leakage currents) as the MEA degrades, and so even a DC measurement of the voltage could be helpful.

Thank you for your assistance.
Best regards,
Michelle Kuykendal
Georgia Tech

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Re: Testing MEA impedance with Matlab

Post  Thomas on Wed Apr 18, 2012 6:20 pm

Dear Michelle,

we offer a DLL that allows to import mcd files into Matlab (MCStream.dll). this one should enable you to get the Ztest.mcd into Matlab.
However I am a bit uncertain, if your concept really adresses the primary problem.

You are stimulating with current. As of Ohms law, we will need a different Voltage (compliance voltage) to drive this current depending on the electrode impedance. Correcting once again to Voltage would not amke to much sense in my eyes.

Cheers

Thomas

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