2021 Day 2: Baseline correction (block average - trange) + Exporting HRF mean
I have two questions:
1) Regarding the parameters we need to insert in the block average function (in the trange) - is minus 2 will always be our best choice to insert in the 'tPre', no matter what is our study design?
2) When I export the HRF mean - in the Time Range option, is it better to insert a time range that includes mostly the peak of the HRF amplitude?
Thank you so much in advance!
I have always used -2 seconds. The idea is to get enough of time before the stimulus that you can get a reasonable average of the "baseline" signal. The Homer functions will subtract this "baseline" signal from the result so that the time from -2 to 0 before the stimulus onset is on average a value of 0 for HbO, HbR, and HbT.
Please bring up the question about export HRF Mean during the class today. In short, yes, choose a time range that includes the peak of the HRF. Let's say your stimulus goes from 0 to 5 sec. In this case we would typically choose a time range from 2 to 5 sec or 3 to 6 sec. We skip the first couple of seconds because the HRF is just growing at that point.