You should just set it to the duration of your event. If all your events are of the same duration, then use that duration. If your events are of different durations, then use the average. This is a scaling parameter, so it will have no effect at all on p-values either at the lower or higher levels. It will only have an effect if you report the percent signal change.
On 8/25/17 9:40 AM, Tori Williams wrote:
Hi FreeSurfer Team,
I was wondering if you could provide a bit more clarification on what the "-refeventdur" flag is referring to in the mkanalysis-sess command? The description in the help screen states it should be the "duration (sec) of reference event for scaling." I am unsure what the "reference event" is. I couldn't find any additional info on the listserv, and the two examples I saw from tutorials used a value of "4" and another used a value of "16". Any clarification is greatly appreciated! Because the help for the flag is listed under the "Assume a shape" header, does it have something to do with the HRF?
Thanks so much! Tori
-- Victoria J. Williams, PhD Clinical Research Fellow
Interdisciplinary Brain Center Massachusetts General Hospital Harvard Medical School Department of Neurology 149 13th Street Charlestown, MA 02129
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