Dear Andy,
to convert onsets in seconds x into onsets in "scans" units y, you have to go with y = x/TR. In your example, the onsets in "scans" units would thus be 6s/3s = 2 and 15s/3s = 5, NOT 3 and 6. See attached screenshot. And if the onset starts at 0 s, then it's indeed 0 scans. Make sure that you also adjust the durations.
This is confusing at first sight. However, if you think about it, at 0 s no data has yet been acquired, so it's indeed appropriate to call it "0 scans". By the way, you're also be able to enter fractions like 0.5 volumes.
To avoid any confusion better go with seconds.
Best,
Helmut
|