hello, in my experiments some participants' auditory P1 responses are below the base line. in terms of wave form I am confident that it is a P1, but below the base line, the same holds also for N1, which is sometimes above the baseline (but it is a N1, depending on latency and wave form characteristics)
what can I do for that? this leads to loss of data.
Quick Clarification
What is the baseline in this case and why is this causing you to lose data?
baseline is the 0 point on voltage axis. when a supposed to be P1 peak is emerging with a negative voltage, then I can not use that value in statistical analysis for that participant. which leads to loss of data especially when comparing P1 amplitudes across conditions.
I definitely understand what you are saying. It is quite a common site. But what we have to look for here is if they are really P1 or not based on the morphology of the wave. If you are confident about it bot worry. Just use peak to peak amplitudes. That should solve your problems. But it would be great if you could post some pics of those waveforms.
I am agree with Nike Sir. Many times I also got P1 and P2 as a negative value. its happens when waveform comes below the baseline. As suggested by Nike Sir, In that case we can take peak-to-peak amplitude to solve such proble. I don't think you have to waste your data.If its ALLR you can take P1-N1, N1-P2 and P2-N2. For example if your P1 is -3microvolt and N1 is -8microvolt, then P1-N1 peak to peak amplitude will be 5miscrovolt. Similarly, if your P1 is 1microvolt and N1 is -3 microvolt, the P1-N1 peak to peak will be 4microvolt. Thanks!
Refer published articles, they have taken similar values.Thanks!
Thanks!
But its better to take absolute values, said by some experts.
thank you all for your interest and answers for my topic, they will be very usefull
will post more questions in near future :-)
Mehmet
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