TENT function for estimating HRF

AFNI Message Board
1

Dear AFNI experts,

I am using TENT(0,20,11) in 3dDeconvolve with option “-iresp” to estimate impulse response to the stimuli onset.
(Here, TR = 2 sec)
In the event-related design, time difference between the onsets of the visual stimuli are ranged from 4 sec to 12 sec (InterStimuli-Interval: ISI).
Is using 11 TENT coefficients acceptable given that the ISI ranges from 4 sec to 12 sec?
I would like to estimate the impulse response in hippocampus, which is known to respond slowly after stimuli onset.
That is why I need to capture the response up to 20 sec, however, I am concerned that I cannot reliably estimate the response because of
short ISI in my experiment design.

Sincerely,
Sungshin Kim

2

I am concerned that I cannot reliably estimate the response because of short ISI in my experiment design.

Run your 3dDeconvolve script, and pay attention to any warning on the screen regarding the correlations for the design matrix. Any potential issue should show up there.