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Signal detection
In this example, we are performing the EDA analysis on the Stroop task. There are 3 focus areas:
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If you see the following error, you need to adjust the threshold:
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ADD SCREENSHOT OF THE SIGNAL WITH MARKERS
EPOCH WIDTH IS A CHOICE. NEED TO FIND OUT WHAT CHOICE IS THE BEST.
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Event type: EDA → Skin Conductance Response
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In the next window, you can the select what measures you want exported: Event count: how many SCRs were found in the focus area Value: the signal value at the marker location (or epoch onset location); this should theoretically be the same as Maximum Maximum: peak value of the SCR Minimum: this is important! You cannot interpret the amplitude of the SCR without considering the baseline!For example, your baseline might be 8.5 and the maximum 10.8 microsiemens. 10.8 microsiemens is NOT the amplitiude of the SCR! the amplitude is 10.8 minus 8.5 microsiemens. So we have to either request an amplitude measurement or subtract the minimum from the maximum. |
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Each epoch is one SCR and the values you requested in the previous step are listed in order.
WHY DOES IT SAY EVENT COUNT 2 for epoch 2?
Alternative analysis
This analysis is part of a Biopac video tutorial. What it does is, it asks you to select an area around the SCR (from the onset to the peak but that can be widened) and then it exports summary measures for this selected period. The problem with that is that we do not care about the mean and standard deviation of the signal between onset and peak of the SCRs. Using the minimum, maximum and number of SCRs is still useful. Instead of this analysis, I recommend the epoch analysis.
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When you select Event amplitude, the following window pops up. We select “Amplitude at first event only”. This might cause the event amplitude and count to be zero.
When you select Event count, select where you want to look for the events and select your EDA channel that contains the water droplet markers.
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