Download Microelectrode Array (MEA) User Manual

Stimulation
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 user manual for the respective MEA amplifier and
stimulus generator for more details. As an alternative, you can also use special MEAs with four
pairs of large (250x50 µm) stimulating electrodes (MEA 200/30-stim) 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
e. g. 10 Hz. 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.
Figure 4
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.
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