Monitoring the stimulated electrode

Sounds little but silly but..

When I use voltage mode, is it safe to apply stimulation without switching the corresponding electrode to ground? That is, is there any harmful effect except output saturation when I apply voltage pulse directly to amplifier? The purpose is I want to see the direct reponse of the cell after the stimulation though the electrode.

Thanks...

Dear Johnny,

it is not possible to directly stimulate an MEA - electrode and monitor the corresponding response of the same MEA electrode by not-switching off the amplifier input.

The result will be a massive stimulation artifact over all MEA electrodes (you may give it a try to see what happens). The time constant for discharging the amp inputs and the MEA electrodes capacitance altogether exceeds the time alg for a cells response - hence you will not be able to see it.

However, what is availabel for the in vivo ME System is a so-called blanking circuit which switches off the amplifier input electronically - hence the stimulation electrode is then readily available for recording.

The BC (blanking circuit) will find its way also to the MEA1060 amplifier of the MEA60 system but this means a toatlly new hardware design of the amplifier. Expect a new system to be available in the third quarter of 2003.

regards

Michael

Dr.Michael Fejtl, CSO
Multi Channel Systems GmbH