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When starting Mr. Kick for the first time settings will be more or less
like the ones found in the configuration file ttDefault.mat.
We'll use these settings as the basis and mainly discuss changes to this
setup.
Simple Stimulus-Response
The first example should resemble the following: At some regular interval
we'll stimulate and measure the response, i.e. sample a sequence of data
(a sweep). The stimulation may be electrical, magnetic or any other that
can be trigged by a digital pulse.
This could be used for measuring the Hoffmann reflex, which will be
used as an example: A nerve is stimulated electrically and the response
is measured in the EMG of the enervated muscle.
The settings below are available from the file ttBasic0.mat.
Acquisition
The direct M-response is seen around 15 ms after stimulation. The H-reflex
follows around 40 ms after stimulation (m. Soleus). A sweep length of
100 ms is sufficient. It may be a good idea to include a pre-trig period
of say 20 ms to monitor muscle activity prior to the stimulation.
In order to measure a correct peak-peak value of the M and H-responses
a relatively high sample rate must be applied, e.g. 10 kHz.
Analog Input
For this purpose we'll need only one channel: The EMG from one muscle.
Label that channel, e.g. "Soleus" (clear On/Sampled for all other). The
sample rate should be set to High to achieve the 10 kHz. No filtering
should be applied as this may affect the peak-peak measurement of the
M- and H-responses.
Make sure the Gain or Sensitivity setting reflects the setting of the
EMG amplifier in use. A sensitivity of 500 µV/V might be a reasonable
starting point. The signal of this channel is grouped as EMG, and the
SI-unit is Volt (V). The EMG amplifier in this example supplies voltages
in the range from -10 to +10 V.
Classification: Y-Analysis
Classification will not be in use. But we can still monitor the H-reflex
during data acquisition: Let's display the peak-peak amplitude of the
signal in the time interval from 32 to 52 ms after stimulation. This is
set up in the Y-Analysis section of the Classification settings (lower
left).
You can show/hide the Y-analysis display via the Windows menu. It will
automatically hide as no classification is applied.
Trigger
Trigger settings control the sampling of sweeps, i.e. what will start
(trigger) the acquisition. We want to sample stimulus-responses at a regular
interval, say every four seconds. We'll choose Internal as the trig Mode/Source
for Mr. Kick to control this. In order to avoid anticipation it may be
a good idea not to stimulate exactly every four seconds. By setting Refractory
to 3.5 s and Max Interval to 4.5 s the inter stimuli interval will vary
randomly ±0.5 s around a 4 s mean.
Event Timing
For this simple example we simply connect the trigger input of the stimulator
to the output of event timer #0. In the hardware manual coming with the
MIO-board in use this output is labeled GPCTR0_OUT.
When trigger mode is Internal (or digital external) the output pulse
from event timer #0 is always synchronized to time zero in every sweep.
Only the Duration and Pulse Polarity settings are relevant here: The
Duration controls the duration of the pulse and may be used to control
the duration of the stimulus if the stimulator supports this. Pulse Polarity
should be set to High if the stimulator is trigged by a low-to-high pulse
transition or at high level.
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