Does anyone know how to work with Motor Evoked Potentials (MEPs)?

Dear all,

I am working for the first time with Transcranial Magnetic Stimulation and Motor Evoked Potentials (MEPs). I am recording MEPs' amplitude as the peak-to-peak value. But does anyone know hot to normalize raw MEPs? Somewhere I read z-score, somewhere that is needed a logarithm (but how can I choose the right base?). I can really understand anything about it.

P.S. I must say that I am really new to statistics.