Multi Block design

AFNI Message Board
1

Hi all,

I have a task design in which for one of the condition, a series of shapes (4s) + fixation cross (2s) are repeated 6 times -> total block time of 36 seconds; and for the other condition a series of faces are presented for 4 seconds) + fixation cross (2-6 s with an average of 4seconds) -> total block length 48 seconds.

I used the regress_basis_multi option and I was going to set BLOCK(36,1) and BLOCK(48,1). But when looking at the documentation on 3dDeconvolve I saw that the duration is usually set between 1 and 30 seconds. Should I use a different regression basis then? Maybe a SPMG function?

Thank you!

2

If I've grasped your experimental design correctly, a more sensible approach might involve capturing individual trials of shapes/faces while excluding the fixation periods. In that case, I recommend using BLOCK(4,1) for both conditions. For a more adventurous option, you can try TENT(0,18,10) (assuming a TR of 2 seconds).

Gang Chen