I notice that there's a button named 'small volume' at the lower left corner of the 'Results' window.

When could I use it?

How is it different from performing a 'region of interest' analysis which is also another button appeared after choosing a contrast for Results?

Also, I find the statistical part of SPM very difficult to understand. For example, at specify 1st-level, I can choose canonical HRF, FIR, etc... are there any courses for beginners dealing with that? I couldn't find relevant videos from SPM official web discussing these designs.

Thanks very much in advance!

Yours sincerely,

Andy