Multichannel Systems MEA Manual - Manual (Page 53)

Stimulation
53
8 Stimulation
8.1 Using MEA Electrodes for Stimulation
You can use any MEA electrode(s) for stimulation. Simply connect the stimulus generator outputs to the
MEA amplifier. Please see the manual for the respective MEA amplifier and stimulus generator for more
details. As an alternative, you can also use special 60StimMEA with four pairs of large (250 x 50 μm)
stimulating electrodes and a special stimulation adapter, or target cells with an external electrode for
stimulation. This and the following chapters are intended for helping you to optimize the stimulation with
MEA electrodes.
All electrodes suffer under electrical stimulation, especially under long-term stimulation. The wear depends
on the stimulus and on the electrode type. When stimulating via MEA electrodes and with standard MEA
amplifiers, you will see a stimulus artifact on all amplifier channels during stimulation due to the high
charge that is injected into the circuit, and the following saturation of the filter amplifiers. The time
constant of the stimulus artifact depends on the amplifier bandwidth; if the lower cutoff frequency is quite
low, for example, 1 Hz, the stimulus artifact will be longer than with 10 Hz, for example. In most cases, it
will not be possible to record true signals that are close to the stimulus pulse. This can be avoided by using
a MEA amplifier with blanking circuit. The stimulating electrode can generally not be used for recording in
parallel to stimulation, because the injected charge is so high, and the time constant for discharging so low.
The screen shot shows a prominent stimulus artifact on all channels, followed by a response.
The stimulating electrode No. 61 has been grounded.
The next pictures demonstrate the blanking feature. On the left screen shot, you see the stimulus artifacts
on a non-stimulating electrode without blanking. On the right, you see the same electrode and stimulation
pattern, but with blanking. The stimulus artifacts have been completely avoided, making it possible to
detect signals shortly after the stimulus.